Electrolyte-solution composition and secondary battery using same

Abstract

An electrolyte-solution composition and a secondary battery using the same. The electrolyte-solution composition is configured in contact with an aluminous surface of a cathode. The electrolyte-solution composition includes an electrolyte solution and a hydroxyquinoline compound. With the hydroxyquinoline compound included in the electrolyte-solution composition, oxidation and corrosion occurred on the aluminous surface, which are caused by the electrolyte-solution composition, is reduced. Accordingly, the capacity of the secondary battery is improved, and the occurrence of self-discharge phenomenon is avoided.

Description

[Technical Field]

[0001] This case relates to an electrolyte composition and a secondary battery thereof, and more particularly to an electrolyte composition that improves battery performance through additives and a secondary battery thereof. [Previous Technology]

[0002] In today's rapidly developing technological world, the performance of consumer electronics and electric vehicles is constantly improving, and their energy demand is also increasing. Due to their portability and rechargeability, rechargeable batteries are currently the mainstream energy storage method, and lithium-ion batteries are the type with the greatest development potential.

[0003] Aluminum metal not only possesses advantages such as high conductivity, low density, and low cost, but also forms a natural oxide layer (Al2O3) on its surface that helps resist corrosion. Therefore, aluminum foil is the most common choice as the positive electrode current collector in lithium-ion batteries. However, lithium salts in lithium-ion electrolytes, such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium hexafluorophosphate (LiPF6), and lithium perchlorate (LiClO4), can still oxidize and corrode the aluminum foil, causing aluminum ions to dissolve into the electrolyte, thereby affecting the battery's performance.

[0004] Therefore, it is necessary to provide an electrolyte composition that improves battery performance through additives and a suitable secondary battery thereof, in order to address the deficiencies of the prior art. [Summary of the Invention]

[0005] The purpose of this invention is to provide an electrolyte composition that improves battery performance through additives and a suitable secondary battery thereof. By using hydroxyquinoline compounds as additives in the electrolyte composition, the aluminum foil, acting as the positive electrode, is less susceptible to corrosion and oxidation by the electrolyte composition in contact with it, thereby increasing the capacity of the secondary battery and preventing self-discharge. Furthermore, the proportion of hydroxyquinoline compounds in the electrolyte composition is, for example, between 0.1 wt% and 2.5 wt%, to obtain an electrolyte composition with appropriate viscosity, preventing a decrease in the ionic conductivity of the electrolyte and further improving battery performance.

[0006] To achieve the aforementioned objective, this invention provides an electrolyte composition. The electrolyte composition is assembled onto an aluminum surface in contact with the positive electrode. The electrolyte composition includes an electrolyte and a hydroxyquinoline compound.

[0007] In one embodiment, the electrolyte comprises a lithium salt.

[0008] In one embodiment, the lithium salt includes one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

[0009] In one embodiment, the hydroxyquinoline compound includes one of 8-hydroxyquinoline and 5-aldehyde-8-hydroxyquinoline.

[0010] In one embodiment, the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition is between 0.1 wt% and 2.5 wt%.

[0011] In one embodiment, the viscosity of the electrolyte composition is between 1 mPa·s and 6 mPa·s.

[0012] In one embodiment, the aluminum surface is the surface of the current collector.

[0013] To achieve the aforementioned objective, this invention also provides a secondary battery suitable for an electrolyte composition. The secondary battery includes a positive electrode and an electrolyte composition. The positive electrode includes an aluminum surface. The electrolyte composition is assembled in contact with the aluminum surface, and the electrolyte composition includes an electrolyte hydroxyquinoline compound.

[0014] In one embodiment, the electrolyte comprises a lithium salt.

[0015] In one embodiment, the lithium salt includes one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

[0016] In one embodiment, the hydroxyquinoline compound includes one of 8-hydroxyquinoline and 5-aldehyde-8-hydroxyquinoline.

[0017] In one embodiment, the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition is between 0.1 wt% and 2.5 wt%.

[0018] In one embodiment, the viscosity of the electrolyte composition is between 1 mPa·s and 6 mPa·s.

[0019] In one embodiment, the aluminum surface is the surface of the current collector.

Implementation Method

[0033] Some typical embodiments embodying the features and advantages of this application will be described in detail in the following description. It should be understood that this application can have various variations in different forms without departing from the scope of this application, and the descriptions and drawings herein are for illustrative purposes only and not for limiting this application. Although the numerical ranges and parameters of this application in a broad sense are approximate values, the values ​​will be stated as precisely as possible in specific examples. The term "and / or" includes any or all combinations of one or more of the related listed items. Unless explicitly stated in an operational / working example, all numerical ranges, quantities, values, and percentages disclosed herein (e.g., percentages of angles, durations, temperatures, operating conditions, quantity ratios, and the like) should be understood to be modified by the terms "approximately" or "substantially" in all embodiments. Accordingly, unless indicated in reverse, the numerical parameters stated in this application and the appended claims are approximate values ​​that may vary as needed. For example, each numerical parameter should be interpreted at least according to the number of significant digits and by applying ordinary rounding principles. A range may be expressed in this document as from one endpoint to another or between two endpoints. All ranges disclosed herein include endpoints unless otherwise specified.

[0034] In one embodiment, the electrolyte composition 10 is configured to contact the aluminum surface 21 of the positive electrode 20. The electrolyte composition 10 includes an electrolyte and a hydroxyquinoline compound.

[0035] In this embodiment, the electrolyte includes a lithium salt, and the lithium salt is, for example, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). In other embodiments, the lithium salt is more preferably one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluoromethanesulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

[0036] In one embodiment, the hydroxyquinoline compound includes, for example, 8-hydroxyquinoline, wherein the molecular structure of 8-hydroxyquinoline is shown below.

[0037] In another embodiment, the hydroxyquinoline compound includes, for example, 5-formyl-8-hydroxyquinoline. The molecular structure of 5-formyl-8-hydroxyquinoline is shown below.

[0038] In other embodiments, the hydroxyquinoline compound is selected, for example, from 8-hydroxyquinoline, 5-aldehyde-8-hydroxyquinoline, and combinations thereof. This invention may be modified as needed for practical applications, and is not limited thereto.

[0039] In this embodiment, the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition 10 is between 0.1 wt% and 2.5 wt%. The viscosity of the electrolyte composition 10 is between 1 mPa·s and 6 mPa·s. The aluminum surface 21 is the surface of a current collector. Table 1 below shows the viscosity of the electrolyte composition 10 including different concentrations of hydroxyquinoline compounds. The electrolyte in the electrolyte composition in Table 1 includes 21 m of LiTFSI and 2 m of zinc trifluoromethanesulfonate (Zn(OTf)2). As shown in Table 1, when the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition 10 reaches 3 wt%, the viscosity of the electrolyte composition 10 will be greater than 6 mPa·s, and the excessively high viscosity will cause a decrease in ionic conductivity, and this phenomenon is more obvious at low temperatures. Therefore, by controlling the concentration of hydroxyquinoline compounds, an electrolyte composition 10 with appropriate viscosity can be obtained, preventing the decrease in ionic conductivity in the electrolyte and improving battery performance. Electrolyte composition Viscosity (mPa·s) Electrolyte + 1 wt% 8-hydroxyquinoline 3.485 Electrolyte + 1 wt% 5-aldehyde-8-hydroxyquinoline 3.985 Electrolyte + 3 wt% 8-hydroxyquinoline 6.151 Electrolyte + 3 wt% 5-aldehyde-8-hydroxyquinoline 6.251 Table 1

[0040] Please refer to Figure 1. Figure 1 is a schematic diagram of the structure of a secondary battery to which the electrolyte composition of this embodiment is applicable. In this embodiment, the secondary battery 1 includes a positive electrode 20 and an electrolyte composition 10. The positive electrode 20 includes an aluminum surface 21. The electrolyte composition 10 is assembled in contact with the aluminum surface 21 of the positive electrode 20, and the electrolyte composition 10 includes an electrolyte and a hydroxyquinoline compound. In other embodiments, the secondary battery 1 may, for example, include a positive electrode material coated on the positive electrode 20, but this embodiment is not limited thereto.

[0041] In this embodiment, the electrolyte includes a lithium salt, and the lithium salt is, for example, lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). In other embodiments, the lithium salt is more preferably one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluoromethanesulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

[0042] In one embodiment, the hydroxyquinoline compound includes, for example, 8-hydroxyquinoline.

[0043] In another embodiment, the hydroxyquinoline compound includes, for example, 5-formyl-8-hydroxyquinoline.

[0044] In other embodiments, the hydroxyquinoline compound is selected, for example, from one of 8-hydroxyquinoline, 5-aldehyde-8-hydroxyquinoline, and combinations thereof. This invention may be modified as needed for practical applications, and is not limited thereto.

[0045] In this embodiment, the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition 10 is between 0.1 wt% and 2.5 wt%. The viscosity of the electrolyte composition is between 1 mPa·s and 6 mPa·s. The aluminum surface 21 is, for example, the surface of a current collector. By controlling the concentration of the hydroxyquinoline compound, an electrolyte composition 10 with appropriate viscosity can be obtained, preventing a decrease in the ionic conductivity of the electrolyte and improving the performance of the battery.

[0046] The efficacy of the electrolyte composition of this case will be explained in detail below through experimental tests of comparative and exemplary examples.

[0047] Comparative Example:

[0048] The comparative example is an additive-free electrolyte composition. The electrolyte composition includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0049] Please refer to Figures 2A and 2B. Figures 2A to 2B are, in sequence, SEM images of the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the comparative example of this case. The electrolyte composition contains only 1 μm of LiTFSI. As shown in Figure 2A, after one week of immersion, obvious corrosion was observed on the surface of the aluminum foil. As shown in Figure 2B, after two weeks of immersion, the surface of the aluminum foil was completely corroded.

[0050] Please refer to Figure 3. Figure 3 is a potentiodynamic polarization curve of the electrolyte composition of the comparative example of this case. The electrolyte composition contains only 1 μm of LiTFSI. The potentiodynamic polarization curve was obtained by measurement using a three-electrode system. In the three-electrode system, the working electrode is aluminum foil, the auxiliary electrode is graphite, and the reference electrode is a reversible hydrogen electrode (RHE). The measurement started from the corrosion potential (Ecorr), first performing a potential scan in the cathode direction, and then performing a potential scan in the anodic direction. Before the measurement, the electrodes were immersed in the electrolyte composition for several seconds to ensure a consistent corrosion potential.

[0051] The fitting results of the potentiodynamic polarization curve in Figure 3 are as follows: The corrosion potential is 262.89 mV. The corrosion current (Icorr) is 9.60 μA. The corrosion rate (CR) of the working electrode is 0.1116 mmpy (mm / year). Furthermore, analysis of the aluminum foil after the potentiodynamic polarization test using an energy dispersive X-ray spectrometer (EDS) revealed that the aluminum content on the foil surface was 79.08 wt%. In other words, after the potentiodynamic polarization curve test, approximately 79 wt% aluminum remained on the aluminum foil surface due to corrosion from the electrolyte composition.

[0052] Please refer to Figures 4A to 4C. Figures 4A to 4C are, in sequence, charge-discharge curves of the battery prepared with the electrolyte composition of the comparative example of this case at the 1st, 5th, and 15th cycles. The electrolyte composition consists only of 21 μm of LiTFSI and 2 μm of Zn(OTf)2. The battery prepared with the electrolyte composition is a CR2032 button cell. The cathode of the battery is an aluminum foil coated with lithium vanadium fluorophosphate (LiVPO4F, LVPF), the anode is a zinc foil, and the separator is glass fiber. The charge-discharge test was performed using a 40-channel battery tester. The test conditions were room temperature (25 °C), 2C charge-discharge rate, and a potential window range of 0.6 V to 2.2 V. Table 2 below shows the charge-discharge capacity of the battery at the 1st, 5th, and 15th cycles, and the capacity retention rate at the 15th cycle. 1st lap 5th lap 15th lap Capacity retention rate in the 15th cycle Charging capacity (mAh / g) 116.98 88.10 36.77 31.4% Discharge capacity (mAh / g) 98.84 78.16 33.00 34.4% Table 2

[0053] Please refer to Figure 5. Figure 5 is a battery characteristic curve of the battery prepared with the electrolyte composition of the comparative example of this case after 5 charge-discharge cycles and 24 hours of rest. The electrolyte composition includes 21 μM of LiTFSI and 2 μM of Zn(OTf)2. The battery prepared with the electrolyte composition is a CR2032 button cell. The cathode of the battery is an aluminum foil coated with LVPF, the anode is a zinc foil, and the separator is glass fiber. The charge-discharge test was performed using a 40-channel battery tester. The test conditions were room temperature (25 °C), a charge-discharge rate of 0.2 C, and a potential window range of 0.6 V to 2.2 V. As shown in Figure 5, the battery completed 5 charge-discharge cycles at approximately 25 hours and was rested for 24 to 48 hours. However, from the beginning of the resting period, the battery current showed a significant decreasing trend, which continued until the 48th hour. It can be seen from this that the battery prepared with the electrolyte composition of the comparative example has a significant self-discharge phenomenon.

[0054] First Example:

[0055] Please refer to Figures 6A and 6B. Figures 6A and 6B are SEM images of the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the first exemplary example of this case. The electrolyte composition includes 1 μm of LiTFSI and 0.1 μm of 8-hydroxyquinoline. As shown in Figure 6A, after one week of immersion, only a small amount of corrosion appeared on the surface of the aluminum foil. As shown in Figure 6B, after two weeks of immersion, the area of ​​corrosion on the surface of the aluminum foil increased slightly.

[0056] Figure 7 is a potentiodynamic polarization curve of the electrolyte composition of the first exemplary example of this case. The electrolyte composition includes 1 μM of LiTFSI and 0.1 μM of 8-hydroxyquinoline. The potentiodynamic polarization curve was obtained by measurement using a three-electrode system. In the three-electrode system, the working electrode is an aluminum foil, the auxiliary electrode is graphite, and the reference electrode is a reversible hydrogen electrode (RHE). The measurement started from the corrosion potential (Ecorr), first performing a potential scan in the cathode direction, and then performing a potential scan in the anodic direction. Before the measurement, the electrodes were immersed in the electrolyte composition for several seconds to ensure a consistent corrosion potential.

[0057] The fitting results of the potentiodynamic polarization curve in Figure 7 are as follows: The corrosion potential is 335.66 mV. The corrosion current (Icorr) is 0.421 μA. The corrosion rate (CR) of the working electrode is 4.89 × 10⁻³ (mm / year). Furthermore, analysis of the aluminum foil after the potentiodynamic polarization test using an Energy Dispersive X-ray spectrometer (EDS) revealed that the aluminum content on the foil surface was 84.85 wt%. In other words, after the potentiodynamic polarization curve test, approximately 85 wt% aluminum remained on the aluminum foil surface due to corrosion from the electrolyte composition.

[0058] Please refer to Figures 8A to 8C. Figures 8A to 8C are, in sequence, charge-discharge curves of the battery prepared with the electrolyte composition of the first exemplary example of this case at the 1st, 5th, and 15th cycles. The electrolyte composition includes 21 μM LiTFSI, 2 μM Zn(OTf)2, and 0.1 μM 8-hydroxyquinoline. The battery prepared with the electrolyte composition is a CR2032 button cell. The cathode of the battery is an LVPF-coated aluminum foil, the anode is a zinc foil, and the separator is glass fiber. The charge-discharge test was performed using a 40-channel battery tester. The test conditions were room temperature (25 °C), 2C charge-discharge rate, and a potential window range of 0.6 V to 2.2 V. Table 3 below shows the charge-discharge capacity of the battery at the 1st, 5th, and 15th cycles. As shown in Table 3, the battery prepared with the electrolyte composition of the first exemplary example has a charging capacity of 151.75 mAh / g and a discharging capacity of 140.31 mAh / g in the first cycle, which is significantly better than the charging and discharging capacity of the battery prepared with the electrolyte composition of the comparative example. 1st lap 5th lap 15th lap Charging capacity (mAh / g) 151.75 119.09 40.89 Discharge capacity (mAh / g) 140.31 115.33 39.94 Table 3

[0059] Please refer to Figure 9. Figure 9 is a battery characteristic curve of the battery prepared with the electrolyte composition of the first exemplary example of this case after 5 charge-discharge cycles and 24 hours of rest. The electrolyte composition includes 21 μM of LiTFSI, 2 μM of Zn(OTf)2, and 0.1 μM of 8-hydroxyquinoline. The battery prepared with the electrolyte composition is a CR2032 button cell. The cathode of the battery is an aluminum foil coated with LVPF, the anode is a zinc foil, and the separator is glass fiber. The charge-discharge test was performed using a 40-channel battery tester. The test conditions were room temperature (25 °C), a charge-discharge rate of 0.2C, and a potential window range of 0.6 V to 2.2 V. As shown in Figure 9, the battery completed 5 charge-discharge cycles at approximately 22 hours and was rested for 24 to 46 hours. However, from the beginning to the end of the resting period, the battery current remained consistent and showed no trend of change. Therefore, it can be concluded that the battery made from the electrolyte composition of the first example does not exhibit self-discharge.

[0060] Second example:

[0061] Figures 10A and 10B are SEM images of the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the second exemplary example of this case. The electrolyte composition includes 1 μm of LiTFSI and 0.1 μm of 5-aldehyde-8-hydroxyquinoline. As shown in Figure 10A, after one week of immersion, almost no corrosion occurred on the surface of the aluminum foil. As shown in Figure 10B, after two weeks of immersion, almost no corrosion occurred on the surface of the aluminum foil.

[0062] Figure 11 is a potentiodynamic polarization curve of the electrolyte composition of the second exemplary example of this case. The electrolyte composition includes 1 μm of LiTFSI and 0.1 μm of 5-aldehyde-8-hydroxyquinoline. The potentiodynamic polarization curve was obtained by measurement using a three-electrode system. In the three-electrode system, the working electrode is aluminum foil, the auxiliary electrode is graphite, and the reference electrode is a reversible hydrogen electrode (RHE). The measurement started from the corrosion potential (Ecorr), first performing a potential scan in the cathode direction, and then performing a potential scan in the anodic direction. Before the measurement, the electrodes were immersed in the electrolyte composition for several seconds to ensure a consistent corrosion potential.

[0063] The fitting results of the potentiodynamic polarization curve in Figure 7 are as follows: Corrosion potential is 306.85 mV. Corrosion current (Icorr) is 0.253 μA. Corrosion rate (CR) is 2.94 × 10⁻³ (mm / year). Furthermore, analysis of the aluminum foil after the potentiodynamic polarization test using an Energy Dispersive X-ray spectrometer (EDS) revealed that the aluminum content on the foil surface was 86.30 wt%. In other words, after the potentiodynamic polarization curve test, approximately 86 wt% aluminum remained on the aluminum foil surface due to corrosion from the electrolyte composition.

[0064] Please refer to Figures 12A to 12C. Figures 12A to 12C are, in sequence, charge-discharge curves of the battery prepared with the electrolyte composition of the second exemplary example of this case at the 1st, 5th, and 15th cycles. The electrolyte composition includes 21 μm of LiTFSI, 2 μm of Zn(OTf)2, and 0.1 μm of 5-aldehyde-8-hydroxyquinoline. The battery prepared with the electrolyte composition is a CR2032 button cell. The cathode of the battery is an aluminum foil coated with LVPF, the anode is a zinc foil, and the separator is glass fiber. The charge-discharge test was performed using a 40-channel battery tester. The test conditions were room temperature (25 °C), 2C charge-discharge rate, and a potential window range of 0.6 V to 2.2 V. Table 4 below shows the charge-discharge capacity of the battery at the 1st, 5th, and 15th cycles, and the capacity retention rate at the 15th cycle. As shown in Table 4, the battery of the second exemplary example had a charging capacity of 125.04 mAh / g and a discharging capacity of 114.57 mAh / g in the first cycle, which is superior to the charging and discharging capacity of the battery prepared with the electrolyte composition of the comparative example. Furthermore, the battery of the second exemplary example retained 81.9% of its charging capacity and 86.6% of its discharging capacity in the 15th cycle, which is also significantly better than the approximately 35% capacity retention of the battery prepared with the electrolyte composition of the comparative example. 1st lap 5th lap 15th lap Capacity retention rate in the 15th cycle Charging capacity (mAh / g) 125.04 116.09 102.43 81.9% Discharge capacity (mAh / g) 114.57 110.67 99.18 86.6% Table 4

[0065] Please refer to Figure 13. Figure 13 is a battery characteristic curve of the battery prepared by the electrolyte composition of the second exemplary example of this case after 5 charge-discharge cycles and 24 hours of rest. The electrolyte composition includes 21 μM of LiTFSI, 2 μM of Zn(OTf)2, and 0.1 μM of 5-aldehyde-8-hydroxyquinoline. The battery prepared by the electrolyte composition is a CR2032 button cell. The cathode of the battery is an aluminum foil coated with LVPF, the anode is a zinc foil, and the separator is glass fiber. The charge-discharge test was performed using a 40-channel battery tester. The test conditions were room temperature (25 °C), a charge-discharge rate of 0.2C, and a potential window range of 0.6 V to 2.2 V. As shown in Figure 13, the battery completed 5 charge-discharge cycles at approximately 22 hours and was rested for 24 to 46 hours. However, from the beginning to the end of the resting period, the battery current remained consistent and showed no trend of change. Therefore, it can be concluded that the battery made from the electrolyte composition of the second example does not exhibit self-discharge.

[0066] The experimental test results of the comparative example, the first exemplary example, and the second exemplary example were compared. Based on the surface morphology SEM images and the fitting results of the potentiodynamic polarization curves, the electrolyte compositions of the first and second exemplary examples showed a significant reduction in the corrosion rate of the aluminum foil compared to the comparative example. In other words, compared to the electrolyte composition without additives, the electrolyte composition including hydroxyquinoline compounds is less prone to oxidation and corrosion of the aluminum foil, with the second exemplary example, which includes 5-aldehyde-8-hydroxyquinoline, being particularly superior. According to the charge-discharge curves, the charge-discharge capacity of the batteries in the first and second exemplary examples was superior to that of the battery in the comparative example, and the capacity retention rate of the battery in the second exemplary example was significantly improved compared to the comparative example. Furthermore, according to the battery characteristic curves, the batteries in the first and second exemplary examples showed no self-discharge phenomenon compared to the comparative example. Therefore, it can be concluded that the electrolyte composition including hydroxyquinoline compounds can improve battery performance and prevent self-discharge.

[0067] In summary, this invention provides an electrolyte composition for improving battery performance through additives and a suitable secondary battery thereof. By using hydroxyquinoline compounds as additives in the electrolyte composition, the aluminum foil, serving as the positive electrode, is less susceptible to corrosion and oxidation by the electrolyte composition in contact with it, thereby increasing the capacity of the secondary battery and preventing self-discharge. Furthermore, the proportion of hydroxyquinoline compounds in the electrolyte composition is, for example, between 0.1 wt% and 2.5 wt%, to obtain an electrolyte composition with appropriate viscosity, preventing a decrease in the ionic conductivity of the electrolyte and further improving battery performance.

[0068] This case can be modified in various ways by a person skilled in this technology, but all of them are subject to the protection sought by the appended patent application. [Simplified Explanation of the Diagram]

[0020] Figure 1 is a schematic diagram of the structure of a secondary battery to which the electrolyte composition of an embodiment of this case is applicable.

[0021] Figures 2A to 2B are SEM images of the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the comparative example of this case.

[0022] Figure 3 is a potentiodynamic polarization curve of the electrolyte composition of the comparative example in this case.

[0023] Figures 4A to 4C are charge-discharge curves of batteries made from the electrolyte composition of the comparative example of this case at different numbers of cycles.

[0024] Figure 5 is a characteristic curve of the battery prepared by the electrolyte composition of the comparative example of this case after being left to stand after charging and discharging.

[0025] Figures 6A to 6B are SEM images of the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the first exemplary example of this case.

[0026] Figure 7 is a potentiodynamic polarization curve of the electrolyte composition of the first exemplary example of this case.

[0027] Figures 8A to 8C are charge-discharge curves of the battery prepared by the electrolyte composition of the first exemplary example of this case at different numbers of cycles.

[0028] Figure 9 is a characteristic curve of the battery made from the electrolyte composition of the first exemplary example of this case after being left to stand after charging and discharging.

[0029] Figures 10A to 10B are SEM images of the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the second exemplary example of this case.

[0030] Figure 11 is a potentiodynamic polarization curve of the electrolyte composition in the second exemplary example of this case.

[0031] Figures 12A to 12C are charge-discharge curves of the battery prepared by the electrolyte composition of the second exemplary example of this case at different numbers of cycles.

[0032] Figure 13 is a characteristic curve of the battery made from the electrolyte composition of the second exemplary example of this case after being left to stand after charging and discharging.

Claims

1. An electrolyte composition configured to contact an aluminum surface of a positive electrode, wherein the electrolyte composition comprises: One electrolyte; And hydroxyquinoline compounds.

2. The electrolyte composition as claimed in claim 1, wherein the electrolyte comprises a lithium salt.

3. The electrolyte composition as claimed in claim 2, wherein the lithium salt comprises one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

4. The electrolyte composition of claim 1, wherein the hydroxyquinoline compound comprises one of 8-hydroxyquinoline and 5-aldehyde-8-hydroxyquinoline.

5. The electrolyte composition as claimed in claim 1, wherein the hydroxyquinoline compound has a weight percentage concentration between 0.1 wt% and 2.5 wt% relative to the electrolyte composition.

6. The electrolyte composition as claimed in claim 1, wherein the viscosity of the electrolyte composition is in the range of 1 mPa·s to 6 mPa·s.

7. The electrolyte composition as claimed in claim 1, wherein the aluminum surface is the surface of a current collector.

8. A secondary battery, comprising: A positive electrode, comprising an aluminum surface; and an electrolyte composition, assembled in contact with the aluminum surface, wherein the electrolyte composition comprises: an electrolyte; And hydroxyquinoline compounds.

9. The secondary battery as claimed in claim 8, wherein the electrolyte comprises a lithium salt.

10. The secondary battery as claimed in claim 9, wherein the lithium salt comprises one of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium bis(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

11. The secondary battery as claimed in claim 8, wherein the hydroxyquinoline compound includes one of 8-hydroxyquinoline and 5-aldehyde-8-hydroxyquinoline.

12. The secondary battery as claimed in claim 8, wherein the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition is between 0.1 wt% and 2.5 wt%.

13. The secondary battery as claimed in claim 8, wherein the viscosity of the electrolyte composition is in the range of 1 mPa·s to 6 mPa·s.

14. The secondary battery as claimed in claim 8, wherein the aluminum surface is the surface of a current collector.

Images