Electrolyte composition and secondary battery using the same

Abstract

An electrolyte composition and a secondary battery using the same. The electrolyte composition is configured to contact an aluminum surface of a positive electrode. The electrolyte composition includes an electrolyte and a hydroxyquinoline compound. The aluminum surface is less likely to be corroded and oxidized by the electrolyte composition with which it is in contact, due to the hydroxyquinoline compound included in the electrolyte composition, thereby improving the capacity of the secondary battery and preventing the occurrence of self-discharge.

Description

Technical Field

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

[0002] In today's rapidly developing technological world, the performance of consumer electronics and electric vehicles is constantly improving, leading to a corresponding increase in their energy demands. Due to their portability and rechargeability, rechargeable batteries are currently the mainstream energy storage method, with lithium-ion batteries being 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 and thus affecting battery 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, 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.

[0006] To achieve the aforementioned objectives, the present invention provides an electrolyte composition. The electrolyte composition is assembled onto an aluminum surface in contact with a 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 hydroxyquinoline compound has a weight percentage concentration between 0.1 wt% and 2.5 wt% relative to the electrolyte composition.

[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 objectives, the present invention further 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 disposed 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 hydroxyquinoline compound has a weight percentage concentration between 0.1 wt% and 2.5 wt% relative to the electrolyte composition.

[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. Attached Figure Description

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

[0021] Figures 2A to 2BSEM 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 the present invention.

[0022] Figure 3 This is a potentiodynamic polarization curve of the electrolyte composition of the comparative example of the present invention.

[0023] Figures 4A to 4C The above are charge-discharge curves of batteries made from the electrolyte composition of the comparative examples of the present invention at different numbers of cycles.

[0024] Figure 5 The image shows the battery characteristics of a battery prepared using the electrolyte composition of a comparative example of the present invention after being left to stand after charging and discharging.

[0025] Figures 6A to 6B SEM images of the surface morphology of aluminum foil subjected to one-week and two-week immersion tests using the electrolyte composition of the first exemplary embodiment of the present invention.

[0026] Figure 7 This is a potentiodynamic polarization curve of the electrolyte composition of the first exemplary example of the present invention.

[0027] Figures 8A to 8C The image shows the charge-discharge curves of a battery made from the electrolyte composition of the first exemplary embodiment of the present invention at different numbers of cycles.

[0028] Figure 9 The battery characteristic curves of the battery prepared by the electrolyte composition of the first exemplary example of the present invention after being left to stand after charging and discharging are shown.

[0029] Figures 10A to 10B SEM images of the surface morphology of aluminum foil subjected to one-week and two-week immersion tests using the electrolyte composition of the second exemplary embodiment of the present invention.

[0030] Figure 11 This is a potentiodynamic polarization curve of the electrolyte composition of the second exemplary example of the present invention.

[0031] Figures 12A to 12C The image shows the charge-discharge curves of a battery prepared using the electrolyte composition of the second exemplary embodiment of the present invention at different numbers of cycles.

[0032] Figure 13 The battery characteristic curves of the battery prepared by the electrolyte composition of the second exemplary example of the present invention after being left to stand after charging and discharging are shown. Detailed Implementation

[0033] Some typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the invention can be varied in different ways without departing from its scope, and the descriptions and drawings herein are illustrative in nature and not intended to limit the invention. Although the numerical ranges and parameters of the broad scope of the invention 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., angles, durations, temperatures, operating conditions, quantity ratios, and such percentages) 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 the present invention 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 herein as from one endpoint to another or between two endpoints. All scopes 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 comprises 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(fluorosulfonyl)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]

[0038] In another embodiment, the hydroxyquinoline compound includes, for example, 5-formyl-8-hydroxyquinoline. The molecular structure of 5-formyl-8-hydroxyquinoline is shown below.

[0039]

[0040] In other embodiments, the hydroxyquinoline compound is selected, for example, from 8-hydroxyquinoline, 5-aldehyde-8-hydroxyquinoline, and combinations thereof. The invention can be modified to suit specific application needs and is not limited thereto.

[0041] 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 ranges from 1 mPa·s to 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 containing 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. Excessive viscosity will cause a decrease in ionic conductivity, and this phenomenon is more pronounced 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.

[0042] Table 1

[0043] Electrolyte composition Viscosity (mPa·s) Electrolyte + 1 wt% 8-hydroxyquinoline 3.485 Electrolyte + 1 wt% 5-aldehyde-8-hydroxyquinoline 3.985 Electrolyte + 3wt% 8-hydroxyquinoline 6.151 Electrolyte + 3wt% 5-aldehyde-8-hydroxyquinoline 6.251

[0044] Please refer to Figure 1 . Figure 1 This is a schematic diagram of the structure of a secondary battery to which the electrolyte composition of an embodiment of the present invention 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 the present invention is not limited thereto.

[0045] In this embodiment, the electrolyte comprises 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(fluorosulfonyl)imide (LiFSI), lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), and lithium tetrafluoroborate (LiBO4).

[0046] In one embodiment, the hydroxyquinoline compound includes, for example, 8-hydroxyquinoline.

[0047] In another embodiment, hydroxyquinoline compounds include, for example, 5-formyl-8-hydroxyquinoline.

[0048] In other embodiments, the hydroxyquinoline compound is selected, for example, from 8-hydroxyquinoline, 5-aldehyde-8-hydroxyquinoline, and combinations thereof. The invention can be modified to suit specific application needs and is not limited thereto.

[0049] 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 ranges from 1 mPa·s to 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.

[0050] The efficacy of the electrolyte composition of the present invention will be explained in detail below through experimental tests of comparative and exemplary examples.

[0051] Comparative example:

[0052] The comparative example is an additive-free electrolyte composition. The electrolyte composition includes lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0053] Please refer to Figures 2A to 2B . Figures 2A to 2B The images shown 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 invention. The electrolyte composition contains only 1 μm of LiTFSI. Figure 2A As shown, after a week of soaking, obvious corrosion appeared on the surface of the aluminum foil. For example... Figure 2B As shown, after two weeks of soaking, the surface of the aluminum foil was completely corroded.

[0054] Please refer to Figure 3 . Figure 3 This is a potentiodynamic polarization curve of the electrolyte composition of the comparative example of the present invention. The electrolyte composition contains only 1 μm of LiTFSI. The potentiodynamic polarization curves were obtained by 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 self-corrosion potential (E) was measured. corr To begin, a potential scan is performed first in the cathode direction, followed by a potential scan in the anodic direction. Before measurement, both electrodes are immersed in the electrolyte composition for several seconds to ensure a consistent corrosion potential.

[0055] Figure 3The fitting results of the potentiodynamic polarization curves are as follows. The corrosion potential is 262.89 mV. The corrosion current (I0) is... corr The electrodynamic polarization (EMP) was 9.60 μA. The corrosion rate (CR) of the working electrode was 0.1116 mmpy (mm / year). Furthermore, analysis of the aluminum foil after the EMP 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 EMP polarization curve test, approximately 79 wt% aluminum remained on the aluminum foil surface due to corrosion from the electrolyte composition.

[0056] Please refer to Figures 4A to 4C . Figures 4A to 4C The following are charge-discharge curves of batteries prepared using the electrolyte composition of the comparative example of the present invention at the 1st, 5th, and 15th cycles, respectively. The electrolyte composition consists only of 21 μm of LiTFSI and 2 μm of Zn(OTf)2. The batteries prepared using the electrolyte composition are CR2032 button batteries. 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. Charge-discharge tests were performed using a 40-channel battery tester. The test conditions were room temperature (25°C), a 2C charge-discharge rate, and a potential window range of 0.6V to 2.2V. 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.

[0057] Table 2

[0058]

[0059] Please refer to Figure 5 . Figure 5 The image shows the battery characteristics of a battery prepared using the electrolyte composition of the comparative example of the present invention after 5 charge-discharge cycles and a 24-hour resting period. The electrolyte composition includes 21 μM of LiTFSI and 2 μM of Zn(OTf)2. The battery prepared using 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. Charge-discharge tests were 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 0.6V to 2.2V. Figure 5 As shown, the battery completed 5 charge-discharge cycles at approximately 25 hours and was left to rest for 24 to 48 hours. However, from the start of the resting period, the battery current showed a significant decreasing trend, which continued until the 48th hour. This indicates that the battery prepared with the electrolyte composition of the comparative example exhibits significant self-discharge.

[0060] First example:

[0061] Please refer to Figures 6A to 6B . Figures 6A to 6B SEM images show the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the first exemplary embodiment of the present invention. The electrolyte composition includes 1 μm of LiTFSI and 0.1 μm of 8-hydroxyquinoline. Figure 6A As shown, after a week of soaking, only a small amount of corrosion appeared on the surface of the aluminum foil. For example... Figure 6B As shown, after two weeks of soaking, the area of ​​corrosion on the aluminum foil surface increased slightly.

[0062] Figure 7 This is a potentiodynamic polarization curve of the electrolyte composition of the first exemplary embodiment of the present invention. The electrolyte composition includes 1 μM LiTFSI and 0.1 μM 8-hydroxyquinoline. The potentiodynamic polarization curve was obtained by measuring 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 self-corrosion potential (E) was measured. corr To begin, a potential scan is performed first in the cathode direction, followed by a potential scan in the anodic direction. Before measurement, both electrodes are immersed in the electrolyte composition for several seconds to ensure a consistent corrosion potential.

[0063] Figure 7 The fitting results of the potentiodynamic polarization curves are as follows. The corrosion potential is 335.66 mV. The corrosion current (I0) is... corr The current is 0.421 μA. The corrosion rate (CR) of the working electrode is 4.89 × 10⁻⁶. -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.

[0064] Please refer to Figures 8A to 8C . Figures 8A to 8CThe following are charge-discharge curves of a battery prepared using the electrolyte composition of the first exemplary embodiment of the present invention at the 1st, 5th, and 15th cycles. The electrolyte composition comprises 21 μM LiTFSI, 2 μM Zn(OTf)₂, and 0.1 μM 8-hydroxyquinoline. The battery prepared using 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. Charge-discharge tests were performed using a 40-channel battery tester. The test conditions were room temperature (25°C), a 2C charge-discharge rate, and a potential window range of 0.6V to 2.2V. 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.

[0065] Table 3

[0066]

[0067] Please refer to Figure 9 . Figure 9 This is a battery characteristic curve of a battery prepared using the electrolyte composition of the first exemplary embodiment of the present invention, after 5 charge-discharge cycles and a 24-hour resting period. The electrolyte composition includes 21 μM LiTFSI, 2 μM Zn(OTf)₂, and 0.1 μM 8-hydroxyquinoline. The battery prepared using the electrolyte composition is a CR2032 button cell. The cathode of the battery is LVPF-coated aluminum foil, the anode is zinc foil, and the separator is glass fiber. Charge-discharge tests were 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 0.6V to 2.2V. Figure 9 As shown, the battery completed 5 charge-discharge cycles at approximately 22 hours and was then left to rest for 24 to 46 hours. However, from the beginning to the end of the resting period, the battery current remained consistent without any change. Therefore, it can be concluded that the battery prepared using the electrolyte composition of the first exemplary example does not exhibit self-discharge.

[0068] Second example:

[0069] Figures 10A to 10B SEM images showing the surface morphology of aluminum foil after one-week and two-week immersion tests using the electrolyte composition of the second exemplary embodiment of the present invention. The electrolyte composition comprises 1 μm of LiTFSI and 0.1 μm of 5-aldehyde-8-hydroxyquinoline. Figure 10A As shown, after a week of soaking, almost no corrosion occurred on the surface of the aluminum foil. For example... Figure 10B As shown, after two weeks of soaking, the aluminum foil surface still showed almost no corrosion.

[0070] Figure 11 This is a potentiodynamic polarization curve of the electrolyte composition of the second exemplary embodiment of the present invention. The electrolyte composition includes 1 μM of LiTFSI and 0.1 μM of 5-aldehyde-8-hydroxyquinoline. The potentiodynamic polarization curve was obtained by measuring 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 self-corrosion potential (E) was measured. corr To begin, a potential scan is performed first in the cathode direction, followed by a potential scan in the anodic direction. Before measurement, both electrodes are immersed in the electrolyte composition for several seconds to ensure a consistent corrosion potential.

[0071] Figure 7 The fitting results of the potentiodynamic polarization curves are as follows. The corrosion potential is 306.85 mV. The corrosion current (I0) is... corr The λ was 0.253 μA. The corrosion rate (CR) was 2.94 × 10⁻⁶. -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.

[0072] Please refer to Figures 12A to 12C . Figures 12A to 12CThe following are charge-discharge curves of a battery prepared using the electrolyte composition of the second exemplary embodiment of the present invention at the 1st, 5th, and 15th cycles. The electrolyte composition comprises 21 μM LiTFSI, 2 μM Zn(OTf)₂, and 0.1 μM 5-aldehyde-8-hydroxyquinoline. The battery prepared using 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. Charge-discharge tests were performed using a 40-channel battery tester. The test conditions were room temperature (25°C), a 2C charge-discharge rate, and a potential window range of 0.6V to 2.2V. 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 made 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 made with the electrolyte composition of the comparative example.

[0073] Table 4

[0074]

[0075] Please refer to Figure 13 . Figure 13 The image shows the battery characteristics of a battery prepared using the electrolyte composition of the second exemplary embodiment of the present invention, after 5 charge-discharge cycles and a 24-hour resting period. The electrolyte composition includes 21 μM LiTFSI, 2 μM Zn(OTf)₂, and 0.1 μM 5-aldehyde-8-hydroxyquinoline. The battery prepared using this 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. Charge-discharge tests were 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 0.6V to 2.2V. Figure 13 As shown, the battery completed 5 charge-discharge cycles at approximately 22 hours and was then left to rest for 24 to 46 hours. However, from the beginning to the end of the resting period, the battery current remained consistent without any change. Therefore, it can be concluded that the battery prepared using the electrolyte composition of the second example does not exhibit self-discharge.

[0076] 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 significantly reduced 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 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 electrolyte compositions including hydroxyquinoline compounds can improve battery performance and prevent self-discharge.

[0077] 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.

[0078] This invention may be modified in various ways by those skilled in the art, but all modifications shall not deviate from the scope of protection sought in the appended patent application.

Claims

1. An electrolyte composition configured to contact an aluminum surface of a positive electrode, wherein the electrolyte composition comprises: One electrolyte; as well as A hydroxyquinoline compound, wherein the hydroxyquinoline compound includes 5-aldehyde-8-hydroxyquinoline.

2. The electrolyte composition of claim 1, wherein the electrolyte comprises a lithium salt.

3. The electrolyte composition of 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 (LiBF4).

4. The electrolyte composition of claim 1, wherein the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition is between 0.1 wt% and 2.5 wt%.

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

6. The electrolyte composition of claim 1, wherein the aluminum surface is the surface of a current collector.

7. A secondary battery, comprising: A positive electrode, comprising an aluminum surface; as well as An electrolyte composition is assembled in contact with the aluminum surface, wherein the electrolyte composition comprises: One electrolyte; as well as A hydroxyquinoline compound, wherein the hydroxyquinoline compound includes 5-aldehyde-8-hydroxyquinoline.

8. The secondary battery of claim 7, wherein the electrolyte comprises a lithium salt.

9. The secondary battery of claim 8, 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 (LiBF4).

10. The secondary battery of claim 7, wherein the weight percentage concentration of the hydroxyquinoline compound relative to the electrolyte composition is between 0.1 wt% and 2.5 wt%.

11. The secondary battery of claim 7, wherein the viscosity of the electrolyte composition is in the range of 1 mPa·s to 6 mPa·s.

12. The secondary battery of claim 7, wherein the aluminum surface is the surface of a current collector.

Images