An electrochemical battery

Abstract

The present invention relates to the technical field of lithium-ion batteries, and in particular to an electrochemical battery, comprising an electrolyte solution, to which an anti-overcharge additive comprising a chloroanisole organic substance and biphenyl is added; the chloroanisole organic substance undergoes a redox reaction on the surface of the positive electrode to form an oxidation product; the biphenyl and the oxidation product undergo an electropolymerization reaction and produce hydrogen; a multilayer composite diaphragm is arranged between the positive electrode and the negative electrode to adsorb the hydrogen; the positive electrode, the negative electrode, and part of the side surface of the multilayer composite diaphragm are separated from the inner wall of the plate positioning sleeve to form a gas accommodating cavity to accommodate the hydrogen flowing out of the multilayer composite diaphragm. The present invention combines two substances with different overcharge prevention mechanisms, a polymerization type and a redox type, to provide multiple overcharge protections by virtue of their complementary advantages, thereby making the electrolyte safer, and reducing the impact of the reaction byproduct hydrogen on battery safety through the multilayer composite diaphragm and the plate positioning sleeve.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to an electrochemical battery. Background Art

[0002] As lithium-ion batteries gain increasing attention as power batteries in areas such as electric bicycles, electric vehicles, and hybrid electric vehicles, the resulting battery safety issues cannot be ignored. Lithium-ion batteries are prone to ignition and even explosion under extreme conditions such as short-circuit, over-discharge, overcharging, heat, and severe impact, severely restricting their promotion and application in the power battery field. Overcharging of lithium-ion batteries can pose a safety hazard if the external protection circuit fails or is misused. Anti-overcharge additives can provide internal overcharge protection for the battery.

[0003] The electrolyte of a lithium-ion battery, typically composed of a lithium salt and a high-purity organic solvent, serves as a carrier for lithium ion migration and charge transfer. Functionally, the anti-overcharge additive added to the electrolyte is a key ingredient influencing lithium battery performance, such as overcharge resistance and high specific energy.

[0004] According to the anti-overcharge principle, anti-overcharge additives can be divided into polymerization type and redox type.

[0005] The working principle of polymer-type anti-overcharge additives is as follows: when the battery is overcharged, the potential reaches the reaction potential of the polymer, causing single molecules to oxidize and produce free radical ions. The free radical ions undergo a polymerization reaction in the electrolyte, and the resulting polymer is deposited on the separator near the positive electrode and extends toward the positive and negative electrodes. At this point, two situations may occur: one is that the polymer forms an electrical bridge between the positive and negative electrodes, causing a micro-short circuit and preventing further voltage increases; the other is that it completely blocks the movement of ions between the positive and negative electrodes, thereby blocking the electrochemical reaction. Therefore, electropolymer additives are irreversible additives.

[0006] The working principle of the redox anti-overcharge additive is: no electrochemical reaction occurs at the normal voltage of the lithium-ion battery, but when the battery is overcharged, the anti-overcharge additive is oxidized near the positive electrode to form active molecules, which then diffuse to the negative electrode and are reduced to form neutral molecules, and then diffuse to the positive electrode. In this way, it constantly shuttles between the positive and negative electrodes, and undergoes redox reactions, consuming the overcharge current, thereby achieving the purpose of anti-overcharge.

[0007] Li Zhijian of Shaanxi University of Science and Technology discovered the potential of adding 2,3-difluorotoluene to lithium-ion battery electrolytes. He investigated its electrochemical properties as an anti-overcharge additive for organic electrolytes, conducting linear sweep voltammetry, constant current and constant voltage charge-discharge tests, electrochemical impedance spectroscopy, and scanning electron microscopy on the lithium-ion batteries. The results showed that the additive, 2,3-difluorotoluene, began to polymerize when overcharged to 4.85V in high-voltage batteries, effectively limiting the charge current. The electrolyte containing 2,3-difluorotoluene exhibited good room-temperature cycling performance in high-voltage ternary batteries, with a capacity retention rate of 67.5% after 100 cycles at 1C.

[0008] Currently, many researchers have tried to use new anti-overcharge additives to solve the problem of lithium-ion battery overcharge and have achieved some results. However, there are still some issues that need to be addressed and addressed in this field:

[0009] Li Bingchuan and others at the Beijing Institute of Chemical Reagents believe that the electropolymerization additives currently used in commercial batteries have a high polymerization potential (4.5-5.5V) and provide good overcharge protection, but they can cause irreversible damage to the battery, and the resulting polymers may also pose a potential safety hazard. Redox couples, as additives to lithium-ion battery electrolytes, do not cause permanent damage to the battery and have little impact on the battery's overall performance, offering great development potential. The search for redox couple additives with high oxidation onset potentials, good solubility, large diffusion coefficients, excellent reversibility, and long cycle life is a key area of ​​research. Combining electropolymerization additives with redox couple additives to compensate for their respective shortcomings is also a promising approach.

[0010] Ma Yulin and others at Harbin Institute of Technology believe that the overcharge performance of lithium-ion batteries depends on various components within the battery system. The simultaneous use of multiple overcharge-resistant components can maximize overcharge safety. Batteries manufactured using overcharge-resistant cathode materials and suitable overcharge-resistant electrolytes, combined with voltage-sensitive separators, will be the future trend.

[0011] For example, the invention patent with application number 200910068034.3 only discloses a method for refining biphenyl in a lithium-ion battery overcharge additive.

[0012] Therefore, how to better combine multiple additives with different anti-overcharge mechanisms to achieve better anti-overcharge effect is a technical problem that needs to be solved. Summary of the Invention

[0013] To this end, the present invention provides an electrochemical battery. By using chloroanisole organic matter and biphenyl, two substances with different anti-overcharge mechanisms, polymerization type and redox type, are used in combination. Multiple overcharge protection is performed by leveraging complementary advantages, making the electrolyte safer. The multi-layer composite diaphragm and plate positioning sleeve are used to reduce the impact of the reaction byproduct hydrogen on battery safety.

[0014] To achieve the above objectives, the present invention provides an electrochemical battery, characterized in that it comprises:

[0015] The electrolyte solution is placed between the positive and negative electrodes of the lithium-ion battery and contains anti-overcharge additives;

[0016] The anti-overcharge additives include chloroanisole organic matter and biphenyl;

[0017] The chloroanisole organic compound can undergo an oxidation-reduction reaction on the positive electrode surface of the lithium-ion battery to form an oxidation product;

[0018] The biphenyl is capable of undergoing an electropolymerization reaction with the oxidation product and generating hydrogen;

[0019] A multi-layer composite diaphragm is provided between the positive electrode and the negative electrode to adsorb the hydrogen;

[0020] The positive electrode, the negative electrode and the multi-layer composite diaphragm are arranged inside the plate positioning sleeve, and part of their side surfaces are separated from the inner wall of the plate positioning sleeve to form a gas accommodating cavity, which is used to accommodate hydrogen flowing out of the multi-layer composite diaphragm.

[0021] Furthermore, the electrolyte solution consists of EC, EMC and DEC;

[0022] The weight percentage of the chloroanisole organic matter in the electrolyte stock solution is 0.1 to 1, and the weight percentage of the biphenyl in the electrolyte stock solution is 1 to 4.

[0023] Furthermore, the multi-layer composite membrane includes a polyethylene layer and a polypropylene layer;

[0024] A layer of the polypropylene layer is provided on each side of the polyethylene layer;

[0025] The outer sides of the two polypropylene layers are coated with a metal organic framework to adsorb the hydrogen.

[0026] In the above scheme, the multi-layer composite membrane of PP / PE / PP has a more uniform microporous structure and better heat resistance than a single-layer membrane, thereby further improving the safety performance of lithium-ion batteries.

[0027] Furthermore, the positive electrode, the negative electrode and the multilayer composite diaphragm are arranged inside the plate positioning sleeve, and part of their side surfaces are separated from the inner wall of the plate positioning sleeve to form a gas accommodating cavity, which is used to accommodate hydrogen flowing out of the multilayer composite diaphragm.

[0028] Furthermore, a safety valve is provided on the side wall of the electrode plate positioning sleeve and passes through both sides, and one end of the safety valve is inserted into the accommodating cavity and aligned with the polyethylene layer.

[0029] Furthermore, at least two electrode groups consisting of the positive electrode, the multi-layer composite diaphragm and the negative electrode are arranged in the electrode plate positioning sleeve;

[0030] The positive electrode, the multi-layer composite separator and the negative electrode of the electrode group are stacked horizontally in order from low to high;

[0031] A metal diaphragm is disposed on the top surface of the negative electrode, and another electrode group is disposed on the upper side of the metal diaphragm.

[0032] Furthermore, the edge of the positive electrode is connected to the positive electrode terminal, the edge of the negative electrode is connected to the negative electrode terminal, and the inner wall of the plate positioning sleeve is provided with two wiring installation grooves, which are respectively embedded in the positive electrode terminal and the negative electrode terminal.

[0033] In the above solution, the safety of the battery and the terminal is further ensured through the structural design of the battery.

[0034] Furthermore, the metal organic framework is a zeolite imidazolate framework compound;

[0035] The zeolite imidazolate framework compound is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone in a mass ratio of 6:100, and stirred uniformly to form a slurry, which is then uniformly coated on the outer sides of the two polypropylene layers by a coating technique.

[0036] Furthermore, the material of the positive electrode active material coating of the positive electrode is NCM622, and the material of the negative electrode active material coating of the negative electrode is graphite, and the graphite has a defective graphene structure for further adsorbing hydrogen.

[0037] Furthermore, the chloroanisole organic compound is 3-chloroanisole;

[0038] The 3-chloroanisole produces a redox reaction on the electrode surface, and its oxidation product and the biphenyl produce an electropolymerization reaction. The specific process of the electropolymerization reaction is:

[0039]

[0040] Furthermore, the anti-overcharge additive further comprises 1 to 10 weight percent of 3-fluoroanisole based on the weight percentage of the electrolyte solution to reduce the exothermic peak when the lithium-ion battery is overcharged.

[0041] In the above scheme, the oxidation product of 3-chloroanisole and biphenyl, two additives with different anti-overcharge mechanisms, are used simultaneously to provide multiple overcharge protections for the battery by virtue of their complementary advantages.

[0042] Compared with the prior art, the present invention has the following advantages:

[0043] 1. Through the use of fluoroanisole-type organic substances, chloroanisole-type organic substances and biphenyl, the two substances with different anti-overcharge mechanisms, polymerization type and redox type, are used in combination. By leveraging their complementary advantages, the battery is provided with multiple overcharge protections at different temperatures and voltages, making the electrolyte safer.

[0044] 2. The multi-layer composite diaphragm of PP / PE / PP reduces the impact of the reaction by-product hydrogen on battery safety, and the microporous structure is more uniform and the heat resistance is better, thereby further improving the safety performance of lithium-ion batteries.

[0045] 3. The structural design of the battery further ensures the safety of the battery and the terminal. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] Figure 1 Schematic diagram of the side structure of the multi-layer composite diaphragm;

[0047] Figure 2 A schematic diagram of the cross-sectional structure of a plate positioning sleeve with a multi-layer composite diaphragm;

[0048] Figure 3 Schematic diagram of the explosion structure of the plate with multi-layer composite diaphragm;

[0049] Figure 4 Schematic diagram of the change of electrochemical impedance of the basic electrolyte before and during overcharging;

[0050] Figure 5 Schematic diagram of changes in electrochemical impedance before and during overcharging for 4% 3-chloroanisole, 0.5% 3-chloroanisole and 3% biphenyl of the present invention;

[0051] Figure 6 Schematic diagram of changes in electrochemical impedance before and during overcharging for 8% 3-chloroanisole, 0.5% 3-chloroanisole and 3% biphenyl of the present invention;

[0052] Figure 7 Schematic diagram of voltage, heat flow and current curves of an electrochemical battery during overcharging at a constant temperature of 30 degrees Celsius according to an embodiment of the present invention;

[0053] Figure 8 Schematic diagram of potentiodynamic polarization curves of electrolytes with different 3-chloroanisole and biphenyl contents according to an embodiment of the present invention.

[0054] Description of the main components in the figure: 1. Negative electrode; 11. Negative electrode terminal; 2. Positive electrode; 21. Positive electrode terminal; 3. Metal-organic framework; 4. Polypropylene layer; 5. Polyethylene layer; 6. Plate positioning sleeve; 61. Fixing sleeve; 7. Safety valve; 8. Electrolyte. DETAILED DESCRIPTION

[0055] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0056] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0057] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0058] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0059] like Figures 1 to 8 As shown, the present invention provides an electrochemical battery, which uses fluoroanisole organic matter, chloroanisole organic matter and biphenyl to achieve the combined use of two substances with different overcharge protection mechanisms, namely polymerization type and redox type. By leveraging their complementary advantages, the battery is provided with multiple overcharge protections at different temperatures and voltages, making the electrolyte safer.

[0060] in, Figure 1 Schematic diagram of the side structure of the multi-layer composite diaphragm; Figure 2A schematic diagram of the cross-sectional structure of a plate positioning sleeve with a multi-layer composite diaphragm; Figure 3 Schematic diagram of the explosion structure of the plate with multi-layer composite diaphragm;

[0061] Figure 4 Schematic diagram of the change of electrochemical impedance of the basic electrolyte before and during overcharging; Figure 5 Schematic diagram of changes in electrochemical impedance before and during overcharging for 4% 3-chloroanisole, 0.5% 3-chloroanisole and 3% biphenyl of the present invention; Figure 6 Schematic diagram of changes in electrochemical impedance before and during overcharging for 8% 3-chloroanisole, 0.5% 3-chloroanisole and 3% biphenyl of the present invention; Figure 7 Schematic diagram of voltage, heat flow and current curves of an electrochemical battery during overcharging at a constant temperature of 30 degrees Celsius according to an embodiment of the present invention; Figure 8 Schematic diagram of potentiodynamic polarization curves of electrolytes with different 3-chloroanisole and biphenyl contents according to an embodiment of the present invention.

[0062] Among them, 1. negative electrode; 11. negative electrode terminal; 2. positive electrode; 21. positive electrode terminal; 3. metal organic framework; 4. polypropylene layer; 5. polyethylene layer; 6. plate positioning sleeve; 61. fixing sleeve; 7. safety valve; 8. electrolyte.

[0063] Example 1:

[0064] like Figures 1 to 3 As shown, this embodiment proposes an electrochemical battery, including an electrolyte solution, which is arranged between the positive electrode 2 and the negative electrode 1 of the lithium-ion battery, and an anti-overcharge additive is added; the anti-overcharge additive includes chloroanisole organic matter and biphenyl; the chloroanisole organic matter can undergo an oxidation-reduction reaction on the surface of the positive electrode 2 of the lithium-ion battery to form an oxidation product; the biphenyl can produce an electropolymerization reaction with the oxidation product and produce hydrogen; a multilayer composite diaphragm is arranged between the positive electrode 2 and the negative electrode 1 to adsorb the hydrogen; the positive electrode 2, the negative electrode 1 and the multilayer composite diaphragm are arranged inside the plate positioning sleeve 6, and part of its side surface is separated from the inner wall of the plate positioning sleeve 6 to form a gas accommodating cavity, and the gas accommodating cavity is used to accommodate the hydrogen flowing out of the multilayer composite diaphragm.

[0065] Furthermore, the multi-layer composite membrane includes a polyethylene layer 5 and a polypropylene layer 4 ; one polypropylene layer 4 is provided on each side of the polyethylene layer 5 ; and the outer sides of the two polypropylene layers 4 are coated with the metal organic framework 3 .

[0066] In the above scheme, the multi-layer composite membrane of PP / PE / PP has a more uniform microporous structure and better heat resistance than a single-layer membrane, thereby further improving the safety performance of lithium-ion batteries.

[0067] Furthermore, the positive electrode 2, the negative electrode 1 and the multilayer composite diaphragm are arranged inside the plate positioning sleeve 6, and part of their side surfaces are separated from the inner wall of the plate positioning sleeve 6 to form a gas accommodating cavity, which is used to accommodate hydrogen flowing out of the multilayer composite diaphragm.

[0068] Furthermore, a safety valve 7 is provided on the side wall of the electrode plate positioning sleeve 6 and passes through both sides. One end of the safety valve 7 is inserted into the accommodating cavity and aligned with the polyethylene layer 5 .

[0069] Furthermore, at least two electrode groups consisting of the positive electrode 2, the multilayer composite diaphragm and the negative electrode 1 are arranged in the electrode plate positioning sleeve 6; the positive electrode 2, the multilayer composite diaphragm and the negative electrode 1 in the electrode group are stacked horizontally in sequence from low to high; a metal diaphragm is arranged on the top surface of the negative electrode 1, and another electrode group is arranged on the upper side of the metal diaphragm.

[0070] Furthermore, the edge of the positive electrode 2 is connected to the positive electrode terminal 21, and the edge of the negative electrode 1 is connected to the negative electrode terminal 11. The inner wall of the plate positioning sleeve 6 is provided with two wiring installation grooves, and the two wiring installation grooves are respectively embedded in and installed with the positive electrode terminal 21 and the negative electrode terminal 11.

[0071] In the above solution, the safety of the battery and the terminal is further ensured through the structural design of the battery.

[0072] Furthermore, the metal-organic framework 3 is a zeolite imidazolate framework compound; the zeolite imidazolate framework compound is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone in a mass ratio of 6:100, and stirred evenly to form a slurry, and the slurry is evenly coated on the outer sides of the two polypropylene layers 4 by coating technology.

[0073] Furthermore, the material of the positive electrode active material coating of the positive electrode 2 is NCM622, and the material of the negative electrode active material coating of the negative electrode 1 is graphite, and the graphite has a defective graphene structure for further adsorbing hydrogen.

[0074] Specifically, a fixing sleeve 61 is provided on the outer wall of the plate positioning sleeve 6 to fix the battery at a desired position.

[0075] Specifically, if Figures 1 to 3As shown, the positive electrode 2, the multi-layer composite separator and the negative electrode 1 are arranged in a horizontal contact manner, which enhances the efficiency of the polymerization and redox reactions of the electrolyte. The different cross-sectional areas further accelerate the reaction.

[0076] More specifically, the micropores of the metal organic framework 3 coated on the side of the polypropylene layer 4 close to the positive electrode 2 are more than or larger than the micropores of the metal organic framework 3 coated on the side of the polypropylene layer 4 close to the negative electrode 1, ensuring that the hydrogen by-product of the polymerization and redox reactions occurring in the positive electrode 2 can be fully adsorbed.

[0077] In this embodiment, the multi-layer composite PP / PE / PP separator reduces the impact of the reaction byproduct hydrogen on battery safety. The resulting microporous structure is more uniform and heat-resistant, further enhancing the safety of the lithium-ion battery. The battery's structural design further ensures the safety of the battery and its terminals.

[0078] Example 2:

[0079] like Figures 1 to 8 As shown, this embodiment proposes an electrochemical battery based on the first embodiment, including an electrolyte stock solution of a lithium ion battery composed of EC, EMC, and DEC, wherein the electrolyte stock solution is added with an anti-overcharge additive, and the anti-overcharge additive includes 1 to 10 weight percentages of fluoroanisole organic matter, 0.1 to 1 weight percentages of chloroanisole organic matter, and 1 to 4 weight percentages of biphenyl, so as to prevent the lithium ion battery from overcharging.

[0080] Furthermore, the fluoroanisole organic compound is 3-fluoroanisole, which is used to prevent the electrolyte solution from self-decomposing at high temperatures. The chemical formula of the 3-fluoroanisole is:

[0081]

[0082] Furthermore, the cut-off voltage of the electrolyte solution does not exceed 5V, so that the 3-fluoroanisole can prevent the lithium-ion battery from overcharging and slow down the heat release during overcharging.

[0083] In the above scheme, 3-fluoroanisole undergoes an electropolymerization reaction at the positive electrode, thereby reducing the exothermic peak of the lithium-ion battery during overcharging, extending the exothermic time, and avoiding severe exothermicity or even explosion of the battery during overcharging.

[0084] Figures 4 to 6This is an electrochemical impedance equivalent fitting diagram drawn through experiments combined with electrochemical impedance spectroscopy. That is, the curve in the figure is the result of fitting the electrochemical impedance spectrum obtained from the experiment. Specifically, the value obtained by the electrochemical impedance spectroscopy fitting is the sum of the ohmic impedance R and the resistance of lithium ions passing through the active material surface. Based on the fitted values, it can be seen that: before overcharging, the electrochemical impedance of the NCM622 half-cells of different electrolyte systems is basically the same, indicating that when overcharging does not occur, the anti-overcharge additive has little effect on the electrochemical impedance of the battery. However, when overcharging occurs, the electrochemical impedance increases, and the increase in electrochemical impedance becomes more obvious with the increase in the 3-fluoroanisole content. The electrochemical impedance of the base electrolyte, the electrolyte with 4% and 8% 3-fluoroanisole additions after overcharging is 8.45Ω, 20.24Ω, and 12.12Ω, respectively. The electropolymerized anti-overcharge additive essentially achieves the purpose of overcharge protection by increasing the internal resistance of the battery after the action. Therefore, when anti-overcharge performance is prioritized, 4% 3-chloroanisole, 0.5% 3-chloroanisole and 3% biphenyl are preferably used by weight.

[0085] See also Figure 7 The heat generation of the battery using the basic electrolyte during the overcharge process is as follows: when the voltage exceeds 4.2V, the heat flow rises slowly. When the voltage exceeds 4.8V, the heat release rises rapidly. The peak of the heat flow curve occurs when the cut-off voltage reaches 5V, and the heat release peak is 140mW / g. After the anti-overcharge additive is introduced, another obvious exothermic peak appears when the voltage reaches around 4.4V. As the amount of 3-fluoroanisole added in the anti-overcharge additive increases, the exothermic peak around 4.4V gradually becomes more obvious and dominates the heat release during the overcharge process. This is because the reaction amount of the electropolymerization reaction of 3-fluoroanisole exceeds the reaction amount of the electropolymerization reaction of biphenyl at this potential. Part of the heat is the heat released when electrical energy is converted into chemical energy during the reaction; the other part of the heat is the heat released when the electropolymerization reaction products adhere to the surface of the positive electrode, increasing the internal resistance of the electrode, consuming the overcharge electrical energy, and directly converting electrical energy into heat energy. When the addition level of 3-fluoroanisole is 5%, the exothermic peak at 4.4V is the strongest, but the peak value is only around 500mW / g, far less than the large amount of heat released during thermal runaway caused by overcharging. Therefore, compared with the violent heat release and even explosion caused by overcharging, the heat release caused by 3-fluoroanisole is slow, which is less likely to cause thermal runaway and fire accidents. The exothermic peak at around 4.4V also proves that 3-fluoroanisole undergoes electropolymerization at this potential.

[0086] Specifically, when the positive electrode surface is coated with a composite membrane containing a zeolite imidazolate framework compound, since the zeolite imidazolate framework compound has the characteristics of high porosity and adjustable porosity, it can prevent the electropolymerization product from being deposited on the surface of the composite membrane and growing along the small pores on the composite membrane and gradually penetrating the composite membrane, thereby avoiding the micro-short circuit inside the lithium-ion battery. The micro-short circuit bridge increases the resistance of the charge when passing through the composite membrane, which, according to Joule's law, causes an increase in the heat release of the battery.

[0087] Furthermore, the chloroanisole organic compound is 3-chloroanisole, and its chemical formula is:

[0088]

[0089] The 3-chloroanisole produces an oxidation-reduction reaction on the electrode surface, and the oxidation product thereof and the biphenyl produce an electropolymerization reaction.

[0090] Furthermore, the process of the electropolymerization reaction between the oxidation product of 3-chloroanisole and biphenyl is specifically as follows:

[0091]

[0092] It should be noted that 3-fluoroanisole does not react with 3-chloroanisole or biphenyl.

[0093] In the above scheme, the battery expansion caused by hydrogen generated when the oxidation product of 3-chloroanisole and biphenyl are used in combination is avoided.

[0094] Furthermore, the metal-organic framework is a zeolite imidazolate framework compound; the electrolyte stock solution contains EC+DEC+EMC at a concentration of 1 mol / L, wherein the mass ratio of EC, DEC, and EMC is 1:1:1; the electrolyte stock solution is added with the biphenyl in an amount of 2 to 4 weight percentages, so that the biphenyl undergoes an electropolymerization reaction while undergoing an electropolymerization reaction with the oxidation product of 3-chloroanisole.

[0095] Specifically, the electrolyte stock solution is a 1 mol / L LiPF6 standard electrolyte, and the solvent is ethylene carbonate (EC) + dimethyl carbonate (DMC) + diethyl carbonate (DEC), (V (EC) : V (DEC) : V (DMC) = 1:1:1). The positive electrode material NCM622 is LiNi 0.6 C o0.2 Mn 0.2 O2.

[0096] See also Figure 8 The polarization curve can be used to study the multi-step complex reaction of the anti-overcharge additives by using the dynamic potential scanning method, and the reaction process of the mixed anti-overcharge additives on the electrode surface can be examined. Figure 8 As can be seen in the figure, the polarization curve of the base electrolyte is essentially a straight line below 5V, indicating that no obvious chemical reaction occurs on the electrode surface. The electrolyte with only 3% biphenyl shows a peak, corresponding to the electropolymerization reaction of biphenyl at this potential. The mixed electrolyte with 0.25% 3-chloroanisole and 4% 3-fluoroanisole added by volume to 3% biphenyl shows two adjacent small peaks (curve e), indicating that two different reactions occur on the electrode surface in this potential range and overlap, but do not completely overlap. When the 3-chloroanisole content is increased to 0.5%, the two reactions completely overlap and form a single peak, as shown in curve d, confirming that the mixed additive does indeed cause two different reactions on the electrode surface.

[0097] Understandably, redox additives are generally stable and reversible, with minimal impact on battery performance. Redox couples dissipate excess current within the battery, limiting the battery voltage to near the additive's oxidation potential. However, their maximum oxidation current depends on the additive's concentration, diffusion coefficient, electrode cross-sectional area, and inter-electrode spacing. Their current-diversion and voltage-limiting capabilities are limited, and their overcharge protection capabilities gradually decline and eventually disappear after multiple cycles, failing to completely resolve the safety issue of battery overcharge. Regarding electropolymer additives, to ensure timely protection against overcharge and prevent accidents, their concentration in the electrolyte is generally increased. This often increases the battery's irreversible capacity loss, resulting in lower charge-discharge efficiency, significantly shortened cycle life, and severe self-discharge. Prolonged storage can lead to a sharp deterioration in battery performance and even malfunction. Therefore, while ensuring battery overcharge safety, the concentration of these additives should be minimized to mitigate their negative impacts. By combining two additives with different overcharge protection mechanisms, the battery can be provided with dual overcharge protection leveraging their complementary advantages.

[0098] Understandably, redox additives are generally stable and reversible, with minimal impact on battery performance. Redox couples dissipate excess current within the battery, limiting the battery voltage to near the additive's oxidation potential. However, their maximum oxidation current depends on the additive's concentration, diffusion coefficient, electrode cross-sectional area, and inter-electrode spacing. Their current-diversion and voltage-limiting capabilities are limited, and their overcharge protection capabilities gradually decline and eventually disappear after multiple cycles, failing to completely resolve the safety issue of battery overcharge. Regarding electropolymer additives, to ensure timely protection against overcharge and prevent accidents, their concentration in the electrolyte is generally increased. This often increases the battery's irreversible capacity loss, resulting in lower charge-discharge efficiency, significantly shortened cycle life, and severe self-discharge. Prolonged storage can lead to a sharp deterioration in battery performance and even malfunction. Therefore, while ensuring battery overcharge safety, the concentration of these additives should be minimized to mitigate their negative impacts. By combining two additives with different overcharge protection mechanisms, the battery can be provided with dual overcharge protection leveraging their complementary advantages.

[0099] Based on the above experimental phenomena and literature reports, it is reasonable to speculate that when the mixed electrolyte is overcharged, the redox reaction of 3-chloroanisole and the electropolymerization of biphenyl occur on the electrode surface, and both of them protect the battery from overcharge. Figure 8 As shown in curve d, the two small voltage plateaus in the charge-discharge test curve correspond to the redox shuttle of 3-chloroanisole and the electropolymerization of biphenyl, respectively. These two overcharge mechanisms work together to prevent further overcharge. However, due to the presence of biphenyl, the oxidation products of 3-chloroanisole may undergo a new electropolymerization reaction with biphenyl, resulting in a lack of a clear 3-chloroanisole reduction peak during the voltage retrace.

[0100] Furthermore, the preparation method of the electrochemical battery includes: step S1, dissolving the fluoroanisole organic matter in a methanol / ether mixed solution and recrystallizing it twice, and drying it under vacuum conditions at 100 degrees for at least 48 hours for purification; step S2, preparing a battery shell for placing electrodes and injecting the electrolyte stock solution; step S3, mixing the chloroanisole organic matter and the biphenyl to form a mixture, and adding the mixture and the fluoroanisole organic matter purified in step S1 to the electrolyte stock solution.

[0101] Specifically, 1.455 g of Co(NO3)2·6H2O and 1.642 g of 2-methylimidazole were dissolved in 40 ml of methanol solution, and then stirred for 10 minutes to dissolve them. The two solutions were mixed and vigorously stirred for 10 minutes, and then settled at room temperature for 48 hours. The purple precipitate was then filtered and repeatedly rinsed with methanol, and finally dried under vacuum conditions at 80 degrees for 24 hours to obtain a zeolite-like imidazole ester framework compound.

[0102] A zeolite imidazolate framework compound was added to a mixed solution of PVDF (polyvinylidene fluoride) and NMP (N-methyl-2-pyrrolidone) in a mass ratio of 6:100. The mixture was then stirred for 24 hours to form a uniform slurry. The prepared polyethylene / polypropylene / polyethylene layers were removed and the slurry was evenly applied to the surface. The slurry was then dried in a vacuum oven at 100 degrees for 12 hours. By controlling the amount of slurry applied, a composite separator with a thickness of approximately 80 microns was obtained. This was then cut into 50 mm diameter discs for battery assembly.

[0103] More specifically, by changing the mass of the zeolite imidazolate framework compound added to the mixed solution, the pore size of the composite membrane is changed, thereby achieving the coating of a metal organic framework with different hydrogen adsorption capabilities near the positive electrode or the negative electrode.

[0104] In the above scheme, the preparation of a battery electrolyte with stronger overcharge resistance is achieved by utilizing the characteristics of high porosity, uniform pore size, and adjustable porosity of the zeolite-like imidazolate framework compound.

[0105] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

[0106] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. An electrochemical battery, characterized in that include: The electrolyte solution is arranged between the positive electrode (2) and the negative electrode (1) of the lithium ion battery and is added with an anti-overcharge additive; The anti-overcharge additives include chloroanisole organic matter and biphenyl; The chloroanisole organic compound can undergo an oxidation-reduction reaction on the surface of the positive electrode (2) of the lithium-ion battery to form an oxidation product; The biphenyl is capable of undergoing an electropolymerization reaction with the oxidation product and generating hydrogen; A multi-layer composite diaphragm is provided between the positive electrode (2) and the negative electrode (1) for adsorbing the hydrogen; The positive electrode (2), the negative electrode (1) and the multi-layer composite diaphragm are arranged inside the plate positioning sleeve (6), and part of the side surface thereof is separated from the inner wall of the plate positioning sleeve (6) to form a gas accommodating cavity, and the gas accommodating cavity is used to accommodate hydrogen flowing out of the multi-layer composite diaphragm; The multi-layer composite diaphragm comprises a polyethylene layer (5) and a polypropylene layer (4); A layer of the polypropylene layer (4) is provided on each side of the polyethylene layer (5); The outer sides of the two polypropylene layers (4) are coated with a metal organic framework (3) to adsorb the hydrogen; The side wall of the electrode plate positioning sleeve (6) is provided with a safety valve (7) penetrating both sides, and one end of the safety valve (7) is inserted into the accommodating cavity and aligned with the polyethylene layer (5); The electrode plate positioning sleeve (6) is provided with at least two electrode groups consisting of the positive electrode (2), the multi-layer composite diaphragm and the negative electrode (1); The positive electrode (2), the multilayer composite diaphragm and the negative electrode (1) of the electrode group are stacked horizontally in order from low to high; A metal diaphragm is provided on the top surface of the negative electrode (1), and another electrode group is provided on the upper side of the metal diaphragm.

2. The electrochemical battery according to claim 1, characterized in that The electrolyte solution consists of EC, EMC and DEC; The weight percentage of the chloroanisole organic matter in the electrolyte stock solution is 0.1 to 1, and the weight percentage of the biphenyl in the electrolyte stock solution is 1 to 4.

3. The electrochemical battery according to claim 1, characterized in that The edge of the positive electrode (2) is connected to the positive electrode terminal (21), and the edge of the negative electrode (1) is connected to the negative electrode terminal (11). The inner wall of the plate positioning sleeve (6) is provided with two wiring installation grooves, and the two wiring installation grooves are respectively embedded and installed in the positive electrode terminal (21) and the negative electrode terminal (11).

4. The electrochemical-based battery according to claim 1, characterized in that The metal organic framework (3) is a zeolite imidazolate framework compound; The zeolite imidazolate skeleton compound is added to a mixed solution of polyvinylidene fluoride and N-methyl-2-pyrrolidone in a mass ratio of 6:100, and stirred evenly to form a slurry, which is then evenly coated on the outer sides of the two polypropylene layers (4) by a coating technique.

5. The electrochemical battery according to any one of claims 1 to 4, characterized in that The material of the positive electrode active material coating of the positive electrode (2) is NCM622, and the material of the negative electrode active material coating of the negative electrode (1) is graphite, and the graphite has a defective graphene structure for further adsorbing hydrogen.

6. The electrochemical battery according to any one of claims 1 to 4, characterized in that The chloroanisole organic compound is 3-chloroanisole; The 3-chloroanisole produces a redox reaction on the electrode surface, and its oxidation product and the biphenyl produce an electropolymerization reaction. The specific process of the electropolymerization reaction is:

7. The electrochemical battery according to any one of claims 1 to 4, characterized in that The anti-overcharge additive further comprises 3-fluoroanisole in an amount of 1 to 10 weight percent of the electrolyte solution, so as to reduce the exothermic peak value when the lithium-ion battery is overcharged.

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