Electrolyte additive as well as synthesis method and application thereof

Abstract

The invention provides an electrolyte additive which has multiple functions when added into an electrolyte, and can stably shuttle between a positive electrode and a negative electrode of an electrochemical device and perform an oxidation reaction at the positive electrode only at a high voltage or an overcharge voltage and a high oxidation-reduction potential, so that an exothermic reaction caused by overcharge of the electrode can be reduced; the electrolyte additive in the oxidation state can shuttle back and forth to the negative electrode to convert the inactive metal into metal ions and reduce the metal ions into the reduction state, the electrolyte additive in the reduction state diffuses back to the positive electrode and can be oxidized again, the inactive metal is effectively recovered through the circular reaction, and the service life of the electrochemical device is greatly prolonged; meanwhile, the electrolyte additive has an interface functional group for generating a beneficial solid electrolyte, and a compact and beneficial solid electrolyte interface layer is generated on the surface of a negative electrode, so that the battery performance is improved.

Description

Technical Field

[0001] The invention relates to an electrolyte additive, in particular to an electrolyte additive used for an electrochemical device.

[0002] One application of the electrolyte additive provided by the present invention is a metal secondary battery, which will be described and illustrated as a preferred embodiment below. However, the present invention is not limited to this single application. Other identical or similar electrochemical devices are all within the scope of equivalent applications covered by the present invention. Background Art

[0003] Although metal batteries have high energy density, low cycle life is a bottleneck that needs to be overcome. The main reason for the performance degradation is the accumulation of inactive metals (for example, lithium, referred to as dead lithium), which may be covered by a poor solid electrolyte interface (SEI), or even completely covered or generate long, discontinuous dendrites, making it impossible for electrons to be effectively transmitted. When these inactive metals continue to accumulate, active metal ions and electrolytes are depleted, and the overly long dendrites also increase the probability of internal short circuits in the battery, causing safety problems. On the other hand, when metal batteries are overcharged, the remaining power increases, and the local voltage on the electrode surface increases exponentially, causing irreversible oxidation of the electrolyte to cause an exothermic reaction, resulting in thermal runaway and serious disasters. Summary of the invention

[0004] In order to solve the problems of the prior art, the present invention provides a method for extending the life of an electrochemical device, the steps of which include: providing an electrochemical device, which at least includes a positive electrode, a negative electrode, and an electrolyte disposed in the electrochemical device, wherein the electrolyte includes an electrolyte additive; charging and discharging the electrochemical device at least once using an overcharge voltage; the electrolyte additive maintains an oxidized state at the positive electrode; the oxidized electrolyte additive shuttles to the negative electrode to oxidize a metal deposited on the negative electrode into a metal ion, so that the electrolyte additive becomes a reduced state and shuttles back to the positive electrode, and restores the oxidized state at the positive electrode.

[0005] The electrochemical device is repeatedly charged and discharged at an overcharge voltage to continuously reduce the metal to the metal ion.

[0006] The metal cannot participate in oxidation-reduction and is an inactive metal.

[0007] The electrochemical device comprises a lithium battery, a sodium battery, a zinc battery, an aluminum battery, a potassium battery, a magnesium battery or a combination thereof or an anode-free battery; and the metal and the metal ion correspond to the metal type of the electrochemical device.

[0008] Among them, the negative electrode generates a beneficial solid electrolyte interface.

[0009] The present invention further provides the above electrolyte additive and a synthesis method thereof, which comprises a compound of the following formula (1):

[0010] Among them, R 1 , R 2 , R 3 , R 4 , R 5 With R 6 It is two or a combination of the following formula (2), formula (3), formula (4) and hydrogen;

[0011]

[0012] Wherein, in formula (2), formula (3) and formula (4), A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not represented are carbon (C) or hydrogen (H).

[0013] From the above description, it can be known that the electrolyte additive suitable for the electrochemical device provided by the present invention has a dual safety mechanism. It can freely and selectively activate the redox function at a high voltage (4.2V~6V), stably shuttle between the positive and negative electrodes, and the additive activates the oxidation potential (state) at the positive electrode in the overcharge state, reducing the exothermic reaction of the electrode caused by overcharging; on the other hand, taking lithium batteries as an example, the oxidized electrolyte additive can shuttle to the negative terminal, convert dead lithium into lithium ions and reduce itself into free radicals, and then shuttle back to the positive electrode for the next cycle of oxidation after the formation of free radicals. Because the dead lithium is effectively revived, the battery life is greatly extended. In addition, this additive has the ability to generate beneficial solid electrolyte interface functional groups (SEI), such as fluorine groups, to generate a beneficial SEI layer on the surface of the negative electrode, thereby improving battery performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a schematic diagram of the steps of a preferred embodiment of the method for synthesizing the compound of formula (5-1) in the first preferred embodiment series of the electrolyte additive of the present invention.

[0015] Figure 2 This is a schematic diagram of the steps of a preferred embodiment of the method for synthesizing the compound of formula (6-1) in the second preferred embodiment series of the electrolyte additive of the present invention.

[0016] Figure 3 This is a schematic diagram of the steps of a preferred embodiment of the method for synthesizing the compound of formula (7-1) in the third preferred embodiment series of the electrolyte additive of the present invention.

[0017] Figure 4This is the dead lithium regeneration mechanism of the electrolyte additive embodiment 3-1 of the present invention in the lithium battery.

[0018] Figure 5A , Figure 5B The cyclic voltammetry data (Cyclic Voltammograms) are respectively for a comparative example without adding the electrolyte additive and a preferred embodiment of the present invention with adding 0.3M of the electrolyte additive.

[0019] Fig. 6A , Figure 6B The voltage profiles are respectively the voltage profiles of the comparative example without the electrolyte additive and the preferred embodiment of the present invention with 0.3M of the electrolyte additive added.

[0020] Figure 7 The linear sweep voltammetric curves are those of a comparative example without the electrolyte additive and a preferred embodiment of the present invention with the electrolyte additive.

[0021] Fig. 8A , Figure 8B The electron microscope images (SEM images) of the control example without the electrolyte additive and the preferred embodiment of the present invention with 0.3M of the electrolyte additive after one round of stripping are shown respectively.

[0022] Fig.9A , Fig. 9B The cross-sectional electron microscope images (FIB-SEM images) of a control example without the electrolyte additive and a preferred embodiment of the present invention with 0.3 M of the electrolyte additive added after one round of stripping are shown.

[0023] Fig. 10A , Fig. 10B The X-ray photoelectron spectra (XPS graphs) of the comparative example without adding the electrolyte additive and the preferred embodiment of the present invention with adding 0.3M of the electrolyte additive are shown respectively.

[0024] Fig.11A , Fig. 11B The results are respectively Titration Gas Chromatography (TGC) analysis of a comparative example without the electrolyte additive and a preferred embodiment of the present invention with the electrolyte additive.

[0025] Fig. 12A , Fig. 12B The inactive metal (dead lithium) content of the comparative example without the electrolyte additive and the preferred embodiment of the present invention with the electrolyte additive are analyzed after several cycles.

[0026] Fig.13The capacitance retention test data of the control example without the electrolyte additive and the preferred embodiment of the present invention with the electrolyte additive are obtained by performing charge and discharge cycle tests using a normal voltage of 4.3V and an overcharge voltage of 4.5V.

[0027] Fig.14 The coulombic efficiency and capacitance retention test data of the comparative example and the preferred embodiment of the present invention tested under 0.2C constant current charge and discharge of the anode-free lithium battery (Cu||NMC Anode Free Cell).

[0028] Fig.15 The coulombic efficiency and capacitance retention test data of the comparative example and the preferred embodiment of the present invention are obtained by charging and discharging a lithium battery (Li||NMC Cell) at 0.2C constant current. DETAILED DESCRIPTION

[0029] <Electrolyte Additives>

[0030] The present invention provides an electrolyte additive comprising the following chemical formula (1):

[0031] Among them, R 1 , R 2 , R 3 , R 4 , R 5 With R 6 It is two or a combination of the following formula (2), formula (3), formula (4) and hydrogen (H).

[0032] Here, elements not shown are carbon (C) or hydrogen (H).

[0033] Wherein, A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof; the remaining unrepresented elements are carbon (C) or hydrogen (H).

[0034] Wherein, A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not represented are carbon (C) or hydrogen (H).

[0035] <First Preferred Embodiment of Electrolyte Additive>

[0036] The electrolyte additive of the present invention, its first preferred embodiment series comprises the following chemical formula (5-1), formula (5-2) or formula (5-3):

[0037] Wherein, A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof; the remaining unrepresented elements are carbon (C) elements.

[0038] Wherein, A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof; the remaining unrepresented elements are carbon (C) elements.

[0039] Wherein, A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof; the remaining unrepresented elements are carbon (C) elements.

[0040] <Second Preferred Embodiment of Electrolyte Additive>

[0041] The electrolyte additive of the present invention, its second preferred embodiment series comprises the following chemical formula (6-1), formula (6-2) or formula (6-3):

[0042] Wherein, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not shown are carbon (C) elements.

[0043] Wherein, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not shown are carbon (C) elements.

[0044] Wherein, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not shown are carbon (C) elements.

[0045] <Third Preferred Embodiment of Electrolyte Additive>

[0046] The electrolyte additive of the present invention, its second preferred embodiment series comprises the following chemical formula (7-1) or (7-2):

[0047] Wherein, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not shown are carbon (C) elements.

[0048] Wherein, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining elements not shown are carbon (C) elements.

[0049] Please refer to the following Tables 1-1 to 1-3, which are several examples of the first to third preferred embodiment series of the above electrolyte additives.

[0050] Table 1-1

[0051]

[0052]

[0053] Table 1-2

[0054]

[0055]

[0056] Table 1-3

[0057]

[0058]

[0059] <Synthesis Method of Electrolyte Additive First Preferred Embodiment>

[0060] Please refer to Figure 1 , for the compound of formula (5-1) in the aforementioned first preferred embodiment series, the preferred embodiment of its synthesis method is:

[0061] use Figure 1 The compounds of formula (8) and formula (9) are reacted with potassium carbonate (K 2 CO 3 ) and acetone environment, the positively charged AH group in formula (8) reacts with the carbon-oxygen bond next to the sulfonic group in formula (9) to obtain a compound of formula (10).

[0062] Next, the compounds of formula (10) and formula (11) are reacted, and the positively charged nitrogen atom in formula (11) reacts with the hydrogen atom on the AH group originally carrying a positive charge in formula (10) to obtain a compound of formula (5-1).

[0063] In the above formula, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining unrepresented elements are carbon (C) elements. It is worth noting that the compounds of formula (5-2) and formula (5-3) in this first preferred embodiment series can be synthesized correspondingly through different substitution positions but in the same synthetic route.

[0064] <Synthesis Method of Electrolyte Additive Second Preferred Embodiment>

[0065] Please refer to Figure 2 For the compound of formula (6-1) in the aforementioned second preferred embodiment series, the preferred embodiment of the synthesis method is:

[0066] use Figure 2 The compound of formula (8) and formula (12) is reacted with potassium carbonate (K 2 CO 3 ) and acetone environment, the positively charged AH group in formula (8) reacts with the carbon-oxygen bond next to the sulfonic group in formula (12) to obtain a compound of formula (13).

[0067] Next, the compound of formula (13) is reacted with the compound of formula (11), and the positively charged nitrogen atom in formula (11) reacts with the hydrogen atom on the AH group originally carrying a positive charge in formula (13) to obtain a compound of formula (6-1).

[0068] In the above formula, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining unrepresented elements are carbon (C) elements. It is worth noting that the compounds of formula (6-2) and formula (6-3) in this second preferred embodiment series can be synthesized correspondingly through different substitution positions but in the same synthetic route.

[0069] <Synthesis Method of Electrolyte Additive Third Preferred Embodiment>

[0070] Please refer to Figure 3, for the compound of formula (7-1) in the aforementioned third preferred embodiment series, the preferred embodiment of its synthesis method is:

[0071] use Figure 3 The compound of formula (14) and the compound of formula (12) are reacted with potassium carbonate (K 2 CO 3 ) and acetone environment, the two positively charged AH groups in formula (14) react with the carbon-oxygen bonds next to the sulfonic groups in two formulas (12) to obtain a compound of formula (15).

[0072] Next, the compound of formula (15) is reacted with two compounds of formula (11). The positively charged nitrogen atoms in the two compounds of formula (11) react with the hydrogen atoms on the two positively charged AH groups in formula (15) to obtain a compound of formula (7-1).

[0073] In the above formula, A also represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, and B represents halogen, nitrile (CN), hydrogen (H), nitro (NO 2 ), nitroso (NO), amine (NH 2 ) or a combination thereof; the remaining unrepresented elements are carbon (C) elements. It is worth noting that the compounds of formula (7-2) in this third preferred embodiment series can be synthesized correspondingly by different substitution positions but in the same synthetic route.

[0074] <Application of Electrolyte Additives>

[0075] The present invention further provides a method for extending the life of an electrochemical device at a high potential by using each preferred embodiment of the aforementioned electrolyte additive, the steps of which include:

[0076] An electrochemical device is provided, which comprises at least a positive electrode, a negative electrode, and an electrolyte disposed in the electrochemical device; the electrolyte comprises the preferred embodiments of the electrolyte additive of the present invention as described above. Preferably, a separator may be included between the positive electrode and the negative electrode if possible.

[0077] The electrochemical device is charged and discharged by using an overcharge voltage, so that the electrochemical device generates an electrochemical reaction; wherein the electrolyte additive preferably maintains an oxidation potential (or an oxidation state) at the positive electrode;

[0078] The electrolyte additive in an oxidized state shuttles to the negative electrode to oxidize an inactive metal deposited on the negative electrode into a metal ion, so that the metal ion re-participates in the electrochemical reaction; and the electrolyte additive becomes a reduced state and shuttles back to the positive electrode, and restores the oxidized state at the positive electrode.

[0079] Step 4 (optional): repeat the above steps 2 to 3 to continue reducing the metal to the metal ion.

[0080] The aforementioned overcharge voltage may have different voltage values ​​for different electrochemical devices. Taking lithium batteries as an example, this overcharge voltage may preferably be 4.2V to 6V, which can start the electrolyte additive to shuttle to the negative electrode, so that the metal is oxidized to the metal ion. Alternatively, the overcharge voltage described in the present invention is a higher voltage for any applicable electrochemical device under commercial implementation. On the other hand, the metal deposited on the negative electrode is preferably referred to as an inactive metal in the present invention. Taking lithium batteries as an example, it is preferably an inactive lithium metal deposited on the negative electrode after starting the electrochemical reaction, which can also be called dead lithium. It is usually coated with a harmful solid electrolyte medium and loses the ability to participate in the electrochemical reaction. The present invention can oxidize the inactive metal back to the metal ion through the electrolyte additive, re-participate in the electrochemical reaction, and maintain the capacitance performance of the electrochemical device.

[0081] The electrochemical device comprises a lithium battery, a sodium battery, a zinc battery, an aluminum battery, a potassium battery, a magnesium battery or a combination thereof. The metal and the metal ion correspond to the type of the electrochemical device. For example, if the electrochemical device is a lithium battery, the metal is lithium metal and the metal ion is a lithium ion. The positive electrode preferably comprises a positive electrode material, and the negative electrode optionally comprises or does not comprise a negative electrode material. If the negative electrode does not comprise the negative electrode material, it is an electrochemical device without a negative electrode (no anode).

[0082] Please refer to Figure 4 The electrochemical device is a lithium battery (the positive electrode comprises a ternary positive electrode material, and the negative electrode is a copper foil) and the electrolyte additive (added to the electrolyte comprises 1M LiPF 6 EC:DEC) is taken as an example of Example 3-1 in Table 1-3 above. Under normal circumstances, its charging potential is 4.2V. The present invention utilizes an overcharge state (greater than 4.2V, such as 4.5V) to keep the electrolyte additive in the state of oxidation potential at the positive electrode ( Figure 4 1 in the figure), which can reduce the exothermic reaction of the positive electrode caused by overcharging; another mechanism is that the oxidized electrolyte additive can shuttle to the negative electrode ( Figure 4 2) converts the lithium metal (or dead lithium) deposited on the negative electrode into lithium ions ( Figure 4 3), the reduced electrolyte additive shuttles back to the positive electrode to be oxidized ( Figure 4 4 in the figure), effectively reviving dead lithium and significantly extending the battery life. The electrolyte additive can even promote the formation of a good solid electrolyte interface (SEI) at the negative electrode.

[0083] <Validity Test>

[0084] The present invention will take the electrochemical device as a lithium battery and the electrolyte additive (added to the electrolyte containing 1M LiPF 6 With EC:DEC) as an example, a series of validation tests were performed.

[0085] Please refer to Figure 5A and Figure 5B , which are respectively the comparative examples without adding the electrolyte additive ( Figure 5A ), adding 0.3M of the electrolyte additive to the preferred embodiment of the present invention ( Figure 5B ) of the cyclic voltammetry data (CV). As can be seen from the figure, the embodiment of the present invention containing the electrolyte additive has stable performance at low and high voltages, indicating that the protection mechanism of the present invention is activated at high voltage and is suitable for operation at high voltage. On the other hand, the comparative example has poor performance after the voltage exceeds 3.96V, and even cannot show normal CV in the 6th cycle, indicating that it cannot operate at high voltage and the electrical properties are greatly reduced.

[0086] Please refer to Fig. 6A and Figure 6B , respectively, the comparative examples without adding the electrolyte additive ( Fig. 6A ), adding 0.3M of the electrolyte additive to the preferred embodiment of the present invention ( Figure 6B ) Voltage Profile. Taking the reference potential of 4.2V as the standard, 4.3V is used before 15 cycles of charge and discharge, and it is increased to a high voltage overcharge state of 4.5V after 15 cycles. Fig. 6A The comparative example shows that in the overcharge state, the battery loses capacity quickly, while the present invention Figure 6B The embodiment still maintains good capacitance and electrical performance under overcharge. From the overcharge test, it can be seen that the embodiment of the present invention containing the electrolyte additive has excellent overcharge adaptability. The electrolyte additive of the present invention can indeed oxidize inactive lithium into lithium ions that can re-participate in electrochemical reactions, thereby maintaining the electrical properties of the battery.

[0087] Please refer to Figure 7 The linear sweep voltammetric curves of the comparative example without the electrolyte additive and the preferred embodiment of the present invention with the electrolyte additive are shown in FIG. Figure 7 It can be seen that the embodiment of the present invention still has stable electrical performance under high voltage (up to 5.2V), indicating that the electrolyte additive of the present invention activates a protection mechanism under high voltage to maintain the electrical properties of the battery.

[0088] Please refer to Fig. 8A and Figure 8B , respectively, the comparative examples without adding the electrolyte additive ( Fig. 8A), the electron microscope images (SEM images) of the preferred embodiment of the present invention with 0.3M of the electrolyte additive after 1 and 5 rounds of stripping, by Fig. 8A and Figure 8B By comparison, it can be seen that the negative electrode surface of the embodiment of the present invention generates a more dense beneficial solid electrolyte interface layer, while the surface of the comparative example is rough, showing irregular lithium dendrites and poor solid electrolyte generation.

[0089] Please refer to Fig.9A and Fig. 9B , respectively, the comparative examples without adding the electrolyte additive ( Fig.9A ), adding 0.3M of the electrolyte additive to the preferred embodiment of the present invention ( Fig. 9B ) Cross-sectional electron microscope images (FIB-SEM images) after 1 and 5 cycles of stripping. Fig.9A and Fig. 9B By comparison, it can be seen that the negative electrode of the embodiment of the present invention forms a thinner solid electrolyte interface layer (SEI). Figures 8A to 9B It can be seen that the electrolyte additive of the present invention can make the lithium battery form a denser and thinner SEI layer. Fig.9A and Fig. 9B The difference in thickness also shows that the electrolyte additive of the present invention activates the oxidation behavior of the inactive metal (such as dead lithium), and also makes the inactive metal originally deposited on the negative electrode recover to active metal ions and re-participate in the electrochemical reaction, and the deposition thickness is also greatly reduced.

[0090] Please refer to Fig. 10A and Fig. 10B , respectively, the comparative examples without adding the electrolyte additive ( Fig. 10A ), X-ray photoelectron spectrum (XPS graph) of the preferred embodiment of the present invention with 0.3M of the electrolyte additive. Comparison of the two phases shows that the embodiment with the electrolyte additive has more benign SEI layer (lithium fluoride LiF) signals in the negative electrode, indicating that the present invention can indeed make the negative electrode produce a benign SEI layer and improve battery characteristics.

[0091] Next, the present invention will Fig.9A and Fig. 9B After the material formed on the negative electrode is scraped off, the scraped material is analyzed by titration gas-liquid chromatography. Since the scraped material contains lithium metal, it reacts with water to generate lithium oxide and hydrogen. The reaction chemical formula is Li+H 2 O→Li 2 O+H 2 , calculate the amount of hydrogen generated, and then infer the amount of inactive lithium (dead lithium) on the negative electrode. Figures 11A to 11B, 12A-12B, which are hydrogen titration gas liquid chromatography (TGC) analysis of a comparative example without adding the electrolyte additive and a preferred embodiment of the present invention with adding the electrolyte additive, respectively, by Fig.11A and Fig. 12A It can be seen that the comparison ratio is compared with Fig. 11B and Fig. 12B The embodiment of the present invention generates more hydrogen and corresponding inactive metals (dead lithium), indicating that the electrolyte additive of the present invention activates a protection mechanism under high voltage to regenerate the inactive lithium (dead lithium) deposited on the negative electrode, thereby achieving the effect of extending the electrical life of the battery.

[0092] Please refer to Fig.13 , which are the capacitance retention test data of the control example without adding the electrolyte additive and the preferred embodiment of the present invention with adding the electrolyte additive, using the normal voltage of 4.3V and the overcharge voltage of 4.5V for the charge and discharge cycle number. Fig.13 It is shown that when the voltage is raised from 4.3V to 4.5V in the 15th charge-discharge cycle, the capacitance retention rate of the present invention even increases, while the capacitance retention rate of the comparative example continues to decrease significantly, indicating that the electrolyte additive of the present invention activates the protection mechanism under high voltage to maintain the electrical properties of the battery.

[0093] Please refer to Fig.14 , the electrochemical device is an anode-free lithium battery (Cu||NMC Anode Free Cell), and the coulombic efficiency and capacitance retention test data of the comparative example (without the electrolyte additive) and the preferred embodiment of the present invention (adding 0.3M of the electrolyte additive) tested under 0.2C constant current charge and discharge. As shown in Figure 11, compared with the comparative example, the embodiment of the present invention still maintains nearly 100% coulombic efficiency and at least 60% capacitance retention when charging and discharging for 100 cycles, while the comparative example consumes almost all of the capacitance at 30 cycles. Therefore, it can be seen that the present invention can indeed extend the life of the electrochemical device and maintain high performance.

[0094] Please refer to Fig.15 , the electrochemical device is a lithium battery (Li||NMC Cell), and the coulombic efficiency and capacitance retention test data of the comparative example (without the electrolyte additive) and the preferred embodiment of the present invention (adding 0.3M of the electrolyte additive) tested under 0.2C constant current charge and discharge. As shown in Figure 12, compared with the comparative example, the embodiment of the present invention still maintains nearly 100% coulombic efficiency and at least 60% capacitance retention when the charge and discharge cycles are higher than 230, while the comparative example consumes almost all of the capacitance at 150 cycles. Therefore, it can be seen that the present invention can indeed extend the life of the electrochemical device and maintain high performance.

Claims

1. A method for extending the life of an electrochemical device, characterized in that: The steps include: An electrochemical device is provided, which comprises at least a positive electrode, a negative electrode, and an electrolyte disposed in the electrochemical device, wherein the electrolyte comprises an electrolyte additive as shown in the following formula (1); Wherein, R1, R2, R3, R4, R5 and R6 are two or a combination of the following formula (2), formula (3), formula (4) and hydrogen; Wherein, in formula (2), formula (3) and formula (4), A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, B represents halogen, nitrile (CN), hydrogen (H), nitro (NO2), nitroso (NO), amine (NH2) or a combination thereof; the remaining unrepresented elements are carbon (C) or hydrogen (H); The electrochemical device is charged and discharged at least once using an overcharge voltage; the electrolyte additive maintains an oxidation potential of an oxidized state at the positive electrode; The electrolyte additive in an oxidized state shuttles to the negative electrode to oxidize a metal deposited on the negative electrode into a metal ion, and the metal ion re-participates in the electrochemical reaction of the electrochemical device; and the electrolyte additive becomes a reduced state and shuttles back to the positive electrode, and restores the oxidized state at the positive electrode.

2. The method for extending the life of an electrochemical device according to claim 1, characterized in that: The electrochemical device is charged and discharged at an overcharge voltage to continuously oxidize the metal into the metal ions.

3. The method for extending the life of an electrochemical device according to claim 1 or 2, characterized in that: The metal cannot participate in oxidation and reduction and is an inactive metal.

4. The method for extending the life of an electrochemical device according to claim 1, 2 or 3, characterized in that: The electrochemical device comprises a lithium battery, a sodium battery, a zinc battery, an aluminum battery, a potassium battery, a magnesium battery or a combination thereof and an anode-free battery; and The metal and the metal ion correspond to the metal species of the electrochemical device.

5. The method for extending the life of an electrochemical device according to claim 1, 2 or 3, characterized in that: The negative electrode creates a beneficial solid electrolyte interface.

6. An electrolyte additive, characterized in that It comprises a compound of the following formula (1), wherein: Wherein, R1, R2, R3, R4, R5 and R6 are two or a combination of the following formula (2), formula (3), formula (4) and hydrogen; Among them, in formula (2), formula (3) and formula (4), A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, B represents halogen, nitrile (CN), hydrogen (H), nitro (NO2), nitroso (NO), amine (NH2) or a combination thereof; the remaining unrepresented elements are carbon (C) or hydrogen (H).

7. The electrolyte additive according to claim 6, characterized in that: The electrolyte additive comprises: R1 and R2 are respectively ortho-substituted chemical formulas of formula (2) and formula (3) of the following formula (5-1); R1 and R3 are respectively the meta-substituted chemical formula of formula (2) and formula (3) of the following formula (5-2); R1 and R4 are respectively the following chemical formula (5-3) of the para-substituted of formula (2) and formula (3); R1 and R2 are respectively ortho-substituted chemical formulas of formula (2) and formula (4) of the following formula (6-1); R1 and R3 are respectively the meta-substituted chemical formula of formula (2) and formula (4) of the following formula (6-2); R1 and R4 are respectively the following chemical formula (6-3) of the para-substituted of formula (2) and formula (4); R1, R2, R4, and R5 are respectively the chemical formula of the following formula (7-1) substituted by formula (2) and formula (4); or R1, R2, R4, and R6 are respectively the chemical formula of the following formula (7-2) substituted by formula (2) and formula (4); 8. The electrolyte additive according to claim 7, characterized in that: The compound of formula (5-1), formula (5-2) or formula (5-3) is reacted with the compounds of formula (8) and formula (9) in a potassium carbonate and acetone environment, and the positively charged AH group in formula (8) reacts with the carbon oxygen bond next to the sulfonyl group in formula (9) to obtain a compound of formula (10); and The compounds of formula (10) and formula (11) are reacted, and the positively charged nitrogen atom in formula (11) reacts with the hydrogen atom on the AH group originally having a positive charge in formula (10) to obtain; Wherein: A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, B represents halogen, nitrile (CN), hydrogen (H), nitro (NO2), nitroso (NO), amine (NH2) or a combination thereof; the remaining unrepresented elements are carbon (C) or hydrogen (H).

9. A method for synthesizing an electrolyte additive, characterized in that: The electrolyte additive comprises the electrolyte additive according to claim 6, 7 or 8: The compound of formula (6-1), formula (6-2) or formula (6-3) is reacted with the compounds of formula (8) and formula (12) in the presence of potassium carbonate (K2CO3) and acetone, where the positively charged AH group in formula (8) reacts with the carbon-oxygen bond next to the sulfonic group in formula (12) to obtain a compound of formula (13); and The compound of formula (13) is reacted with the compound of formula (11), and the positively charged nitrogen atom in formula (11) reacts with the hydrogen atom on the AH group originally having a positive charge in formula (13) to obtain; Wherein: A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, B represents halogen, nitrile (CN), hydrogen (H), nitro (NO2), nitroso (NO), amine (NH2) or a combination thereof; the remaining unrepresented elements are carbon (C) or hydrogen (H).

10. The method for synthesizing the electrolyte additive according to claim 9, characterized in that: The compound of formula (7-1) or formula (7-2) is reacted with two compounds of formula (12) in the presence of potassium carbonate (K2CO3) and acetone, whereby the two positively charged AH groups in formula (14) react with the carbon-oxygen bonds next to the sulfonic groups in the two compounds of formula (12) to obtain a compound of formula (15); and Formula (15) is used to react with two compounds of formula (11), and the positively charged nitrogen atoms in the two formulas (11) react with the hydrogen atoms on the two AH groups originally having positive charges in formula (15) to obtain; Wherein: A represents oxygen (O), sulfur (S), selenium (Se), tellurium (Te) or a combination thereof, B represents halogen, nitrile (CN), hydrogen (H), nitro (NO2), nitroso (NO), amine (NH2) or a combination thereof; the remaining unrepresented elements are carbon (C) or hydrogen (H).

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