Aqueous battery with high cycle performance

Abstract

The invention discloses a high-cycle-performance aqueous battery, which comprises an aqueous electrolyte, a negative electrode, a first positive electrode and a second positive electrode, wherein the first positive electrode and the second positive electrode are positioned on two sides of the negative electrode, and a first diaphragm and a second diaphragm are respectively arranged between the first positive electrode and the negative electrode and between the second positive electrode and the negative electrode; the battery is provided with an electromagnetic valve, the electromagnetic valve is electrically connected with the first positive electrode and the second positive electrode to control switching of the positive electrodes in the charging and discharging loop, and every time discharging and charging circulation are completed, the electromagnetic valve switches the electrode connection relation, and the first positive electrode and the second positive electrode are alternately connected into the charging and discharging loop. Switching of the two positive electrodes in the aqueous battery is accurately controlled through the electromagnetic valve, a positive-negative battery structure is formed in real time, the double positive electrodes alternately perform lithium removal-lithium intercalation reaction, excessive Li intercalation or insufficient positive electrode reduction caused by long-term charging and discharging of a single positive electrode is avoided, the structural stability of the positive electrode material is improved, and the service life of the battery is prolonged. The cycle life and the electrochemical performance stability of the aqueous battery are obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, specifically relating to an aqueous battery with high cycle stability. Background Technology

[0002] Aqueous batteries use aqueous solutions as electrolytes and have advantages such as high safety, environmental friendliness, and high ionic conductivity, making them a promising trend for the next generation of energy storage batteries.

[0003] In aqueous battery systems where LiMn2O4 is used as the positive electrode active material, its poor cycle stability restricts its commercial application. This is because, during the electrochemical reaction process, the Mn... 3+ Its presence leads to a strong Jahn-Teller effect, especially during deep discharge, causing lattice distortion and a transformation from an active cubic spinel structure to an inactive tetragonal phase, inducing grain cracking and resulting in Li... + Irreversible deintercalation and deintercalation occur, disrupting the integrity of the crystal structure and causing the material structure to collapse and become damaged. This leads to the loss of battery active materials, rapid capacity decay, reduced cycle life, and continuous increase in internal resistance, ultimately resulting in battery failure.

[0004] To address the cycling stability issues of aqueous batteries, existing technologies have reported various approaches, including electrolyte modification, electrode material surface coating, and oxide doping. However, these solutions suffer from drawbacks such as complex processes and high costs, or they can only alleviate material loss and structural damage to a certain extent, with limited effectiveness in improving battery cycle performance.

[0005] Therefore, it is necessary to develop an aqueous battery that can reduce the dissolution rate of the cathode material, improve the cycle stability of the battery, and extend its service life. Summary of the Invention

[0006] The purpose of this invention is to provide an aqueous battery with high cycle performance. By designing a dual positive electrode and single negative electrode battery structure, the dissolution rate of the positive electrode material is reduced, the cycle stability is improved, and the battery life is extended.

[0007] The technical solution adopted in this invention is: A high-cycle-performance aqueous battery includes an aqueous electrolyte, a negative electrode, and a first positive electrode and a second positive electrode located on both sides of the negative electrode. A first separator and a second separator are respectively provided between the first positive electrode and the negative electrode, and between the second positive electrode and the negative electrode. The battery is equipped with a solenoid valve, which is electrically connected to the first positive electrode and the second positive electrode respectively, to control the switching of the positive electrode in the charging and discharging circuit, and to alternately connect the first positive electrode and the second positive electrode to the charging and discharging circuit.

[0008] Furthermore, the first positive electrode and the second positive electrode are respectively provided with tabs, and the solenoid valves are electrically connected to the tabs of the first positive electrode and the second positive electrode respectively.

[0009] Furthermore, after each discharge and charge cycle is completed, the solenoid valve switches the electrode connection relationship. Moreover, the solenoid valve switches the electrodes after charging is completed; that is, when the charging process ends, the solenoid valve switches the electrodes, disconnecting the current positive electrode and connecting another set of positive electrodes, alternately connecting the first positive electrode and the second positive electrode to the charging and discharging circuit.

[0010] Furthermore, the solenoid valve has a common connection terminal and two positive connection terminals. The common connection terminal serves as the positive terminal outlet of the battery and is connected to an external charging and discharging circuit. The two positive connection terminals are respectively connected to the first positive terminal and the second positive terminal. The solenoid valve switches its internal path to selectively connect the common connection terminal to one of the two positive terminals: initially, the common connection terminal is connected to the first positive terminal and disconnected from the second positive terminal; when the battery is charged to the cutoff voltage, the solenoid valve switches its path, disconnecting the common connection terminal from the first positive terminal and connecting it to the second positive terminal; then the discharge and charge cycle continues; after the next charge reaches the cutoff voltage, the solenoid valve switches again, connecting the common connection terminal to the first positive terminal and disconnecting it from the second positive terminal; this cycle repeats, and at the end of each charge, the solenoid valve switches its electrodes, disconnecting the current positive terminal and connecting the other set of positive terminals, achieving alternating single connection between the first and second positive terminals.

[0011] Furthermore, tabs are provided on the first positive electrode and the second positive electrode respectively, and the two positive electrode connection terminals of the solenoid valve are selectively connected to one of the tabs of the first positive electrode and the second positive electrode respectively.

[0012] Furthermore, the active materials for both the first and second positive electrodes are lithium manganese oxide. In the initial state of the battery, the active material for the first positive electrode is LiMn₂O₄, and the active material for the second positive electrode is Li₂O₄. 1-x Mn2O4, 0 < x < 1.

[0013] The Li 1-x Mn2O4 can be obtained through synthesis or by delithiation of LiMn2O4 through charging.

[0014] Furthermore, the first and second positive electrodes have the same structure, both including a positive current collector and a positive active layer. The positive active layer includes a positive active material, a positive binder, and a positive conductive agent. The positive active layer is disposed on one side of the positive current collector.

[0015] The positive electrode active material of the first positive electrode is LiMn2O4; the positive electrode active material of the second positive electrode is Li 1- x Mn2O4.

[0016] Preferably, the side of the first or second positive electrode opposite to the negative electrode is provided with a positive electrode active layer.

[0017] The negative electrode includes a negative electrode current collector and a negative electrode active layer, with the negative electrode active layer disposed on both sides of the negative electrode current collector.

[0018] The negative electrode active layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.

[0019] The positive electrode binder is generally one or more of PVDF, PTFE, CMC, SBR, La133, La136D, Na-based bentonite, starch, epoxy resin, polyurethane, polyamide, phenolic resin, and rosin. The positive electrode conductive agent is generally one or more of SP, Ketjen black, acetylene black, graphite, activated carbon, carbon nanotubes, carbon fibers and graphene. The negative electrode active material is a lithium-intercalable material, generally one of lithium titanium phosphate, sodium titanium phosphate, titanium dioxide, and activated carbon; The negative electrode binder is generally one or more of PVDF, PTFE, CMC, SBR, LA133, LA136D, Na-based bentonite, starch, epoxy resin, polyurethane, polyamide, phenolic resin, and rosin. The negative electrode conductive agent is generally one or more of SP, Ketjen black, acetylene black, graphite, activated carbon, carbon nanotubes, carbon fibers, and graphene.

[0020] The electrolyte is an aqueous solution of lithium salt and / or sodium salt, with a concentration of 0.5-18 mol / L, preferably 1-17 mol / L.

[0021] The lithium salt is one or more of Li2SO4, LiOAc, LiClO4, and LiTFSI.

[0022] The sodium salt is one or more of Na2SO4, NaOAc, Na2C2O4, etc., preferably Na2SO4.

[0023] The positive or negative current collector is one of Al foil, stainless steel foil, Cu foil, Ti foil, Zn foil, or graphite paper.

[0024] This invention also provides a method for preparing a high-cycle-performance aqueous battery, the method comprising the following steps: (1) The positive electrode active material, positive electrode binder, and positive electrode conductive agent are mixed, and a solvent is added to prepare a positive electrode slurry. This slurry is coated on one side of the positive electrode current collector and dried to obtain a positive electrode sheet. The positive electrode active material is LiMn2O4, thus obtaining the first positive electrode. The positive electrode active material is Li 1-x Mn2O4 was used to prepare the second cathode, where 0 < x < 1; (2) The negative electrode active material, negative electrode conductive agent and negative electrode binder are mixed, and a solvent is added to make a negative electrode slurry. The slurry is coated on both sides of the negative electrode current collector and dried to obtain the negative electrode. (3) Assemble the first positive electrode, the first diaphragm, the negative electrode, the second diaphragm, and the second positive electrode in that order. The side of the first positive electrode and the second positive electrode coated with the positive electrode slurry faces the negative electrode side respectively. Inject electrolyte, encapsulate, and set up a solenoid valve at the positive electrode position. Connect the solenoid valve to the first positive electrode and the second positive electrode respectively to control the switching of the positive electrode and obtain an aqueous battery.

[0025] Furthermore, in step (1), the positive electrode active material of the second positive electrode is Li. 1-x Mn2O4, Li 1-x Mn2O4 can be obtained through synthesis or by delithiation of LiMn2O4 through charging.

[0026] Li was obtained through a synthetic method. 1-x When Mn2O4 is used, the method in step (1) can be directly followed. 1-x Mn2O4 was used to prepare the positive electrode slurry, and the second positive electrode was prepared.

[0027] LiMn2O4 was charged and delithiated to obtain Li. 1-x When Mn2O4 is used, step (1) is preferably performed as follows: (1-1) LiMn2O4, positive electrode binder and positive electrode conductive agent are mixed, and solvent is added to make a positive electrode slurry. The slurry is coated on one side of the positive electrode current collector and dried to obtain the initial positive electrode sheet. The initial positive electrode sheet serves as the first positive electrode. (1-2) Take the initial positive electrode as the positive electrode, activated carbon as the negative electrode, add electrolyte, assemble to obtain a capacitor, set the N / P ratio of the capacitor to 1.1-3, charge the capacitor to delithiate the initial positive electrode, and obtain a delithiated positive electrode; the delithiated positive electrode is used as the second positive electrode; The active material on the lithium-free cathode is Li 1-x Mn₂O₄, 0 < x < 1; Furthermore, after the capacitor is fully charged, it is disassembled to examine the Li-containing components. 1-x The Mn2O4 electrode is cleaned and dried to obtain a delithiated positive electrode.

[0028] In step (1), the solid content of the positive electrode slurry is 30%-75%, preferably 40%-70%; The mass ratio of LiMn2O4, positive electrode binder, and positive electrode conductive agent is 70~95:2~20:2~10, preferably 75~90:3~15:3~8.

[0029] Furthermore, the viscosity of the positive electrode slurry is 3000-15000 mPa / s, preferably 4000-12000 mPa / s.

[0030] In step (1), the electrolyte is a lithium salt solution with a concentration of 0.1-8 mol / L, preferably 0.5-6 mol / L.

[0031] In step (2), the N / P ratio is 1.1-3, preferably 1.5-2.5.

[0032] In step (3), the mass ratio of the negative electrode active material, the negative electrode conductive agent, and the negative electrode binder is 75~93:2~20:2~10, preferably 80~90:3~15:3~8.

[0033] In step (3), the solid content of the negative electrode slurry is 30%-75%, preferably 40%-70%; The viscosity of the negative electrode slurry is 3000-15000 mPa / s, preferably 4000-12000 mPa / s.

[0034] In step (4), the N / P ratio of the negative electrode to the first positive electrode or the second positive electrode satisfies 0.4≤N / P ratio<1, preferably 0.5-0.8.

[0035] This invention designs an N / P ratio of <1, resulting in an excess of positive electrode material to compensate for the loss and deactivation of the positive electrode active material during charge and discharge cycles. The rated capacity of the battery cell is then calibrated based on the capacity of the negative electrode material.

[0036] The side of the first and second positive electrodes facing the negative electrode is the positive electrode active layer.

[0037] Preferably, the solvent in steps (1) and (3) is one or more of deionized water, NMP, alcohols, carboxylic acid esters, DMF, and dihydro-L-glucanone.

[0038] Preferably, if the solvents in steps (1) and (3) contain multiple solvents, the volume of each solvent shall not exceed 90% of the total volume of the solvents, and more preferably not more than 85%.

[0039] Preferably, in steps (1) and (3), the drying temperature is 50-130 ℃, more preferably 60-120 ℃; After drying, the electrodes are typically rolled, slit, and die-cut to obtain positive or negative electrodes.

[0040] This invention uses LiMn2O4 to prepare the positive electrode, performs Li-removal treatment on a portion of the LiMn2O4, and then, through N / P design, assembles both unremoved and delithiated LiMn2O4 with the negative electrode to form an aqueous battery. The N / P ratio is calculated based on single positive and single negative electrode pieces. Finally, the desired aqueous battery is obtained through liquid injection, encapsulation, and formation. The designed aqueous battery effectively alleviates the capacity decay problem caused by the dissolution and failure of the LiMn2O4 positive electrode, and greatly improves the cycle stability of the battery.

[0041] The charging and discharging process of the aqueous battery of this invention is as follows: (i) Initial charging Initially, the solenoid valve connects the first positive electrode and disconnects the second positive electrode, forming a charging circuit of first positive electrode to negative electrode. Charging begins and continues until the voltage reaches the preset charging cutoff voltage, at which point charging ends. During charging, the LiMn2O4 at the first positive electrode begins to degrade from Li. After charging is complete, the LiMn2O4 at the first positive electrode undergoes degradation to form Li. 1-x Mn2O4; (ii) First discharge After charging is complete, the solenoid valve switches the circuit, disconnecting the first positive electrode and connecting the second positive electrode. The discharge circuit switches to the second positive electrode-negative electrode configuration, initiating discharge until the voltage reaches the preset discharge cutoff voltage, at which point the discharge ends. During discharge, the delithiation of Li from the second positive electrode... 1-x Mn₂O₄ begins to intercalate Li, and after the discharge ends, the Li at the second positive electrode... 1-x Mn2O4 is intercalated with Li to form LiMn2O4; (iii) Cyclic charging and discharging After discharge, the battery maintains the second positive-negative electrode circuit for the next charging cycle. The LiMn2O4 at the second positive electrode begins to degrade from Li until the voltage reaches the preset charging cutoff voltage, at which point the LiMn2O4 at the second positive electrode degrades to form Li. 1-x Mn2O4, the solenoid valve switches the circuit again, disconnecting the second positive electrode and reconnecting the first positive electrode, initiating a new round of discharge; at this time, the delithiation of Li from the first positive electrode... 1-x Mn₂O₄ begins to intercalate Li. After discharge, the Li at the first positive electrode... 1-x Mn2O4 is intercalated with Li to form LiMn2O4; Repeat the above discharge, charge, and solenoid valve switching steps to achieve battery cycle operation.

[0042] When each charging process ends, the solenoid valve switches electrodes, disconnecting the current positive electrode and connecting another set of positive electrodes, thus alternately connecting the first positive electrode and the second positive electrode to the charging and discharging circuit.

[0043] The beneficial effects of this invention are as follows: 1. The aqueous battery designed in this invention has a wide range of applications. Different types of negative electrode materials can be used to form corresponding aqueous batteries, such as aqueous lithium-ion batteries and aqueous lithium / sodium hybrid ion batteries.

[0044] 2. The two positive electrodes of the aqueous battery designed in this invention are unremoved LiMn2O4 and de-Li-treated LiMn2O4, respectively. 1- x Mn2O4, by controlling the charge-discharge sequence, achieves alternating lithium delithiation-lithiation reactions at the dual cathodes, maximizing the utilization of Li. + This avoids excessive Li intercalation or insufficient reduction of the positive electrode due to long-term charging and discharging of a single positive electrode, thereby improving the structural stability of the positive electrode material and preventing the positive electrode material from dissolving, collapsing, and decaying.

[0045] 3. This invention precisely controls the switching of the two positive electrodes in the aqueous battery through an electromagnetic valve, forming a battery structure with one positive and one negative electrode in real time. This effectively avoids material deactivation caused by the overuse of material on one side of the positive electrode, maintains the stability of the N / P ratio of the aqueous battery during cycling, thereby maximizing the electrochemical performance of the battery and significantly improving the cycle life and electrochemical performance stability of the aqueous battery. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the battery structure of the present invention. In the diagram, 1 is the first positive electrode, 2 is the first separator, 3 is the negative electrode, 4 is the second separator, and 5 is the second positive electrode.

[0047] Figure 2 These are the cycle stability curves of Embodiment 1 and Comparative Example 1 of the present invention.

[0048] Figure 3 This is a comparison of the internal resistance of the batteries in Embodiment 1 and Comparative Example 1 under different cycles.

[0049] Figure 4 The Mn content in the electrolyte of the batteries of Example 1 and Comparative Example 1 of this invention at different cycle numbers 2+ Content comparison.

[0050] Figure 5 These are the cyclic stability curves of Embodiment 2 and Comparative Example 2 of the present invention.

[0051] Figure 6 This is a comparison of the internal resistance of the batteries in Embodiment 2 and Comparative Example 2 of the present invention under different cycles.

[0052] Figure 7 The Mn content in the electrolyte of the batteries of Example 2 and Comparative Example 2 of this invention is measured at different cycle numbers. 2+ Content comparison.

[0053] Figure 8 These are the cyclic stability curves of Embodiment 3 and Comparative Example 3 of the present invention.

[0054] Figure 9 These are the cycle stability curves of Embodiment 4 and Comparative Example 4 of the present invention. Detailed Implementation

[0055] The technical solution of the present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0056] A schematic diagram of the high-cycle-performance aqueous battery provided by this invention is shown below. Figure 1 As shown, the battery includes an aqueous electrolyte, a negative electrode 3, and a first positive electrode 1 and a second positive electrode 5 located on both sides of the negative electrode 3. A first separator 2 and a second separator 4 are respectively provided between the first positive electrode 1 and the negative electrode 3, and between the second positive electrode 5 and the negative electrode 3. The battery is equipped with a solenoid valve, which is electrically connected to the first positive electrode 1 and the second positive electrode 5 respectively, and controls the switching of the positive electrode in the charging and discharging circuit: after each discharge and charging cycle is completed, the solenoid valve switches the electrode connection relationship, and alternately connects the first positive electrode 1 and the second positive electrode 5 in the external charging and discharging circuit.

[0057] Furthermore, the first positive electrode 1 and the second positive electrode 5 are respectively provided with tabs, and the solenoid valves are electrically connected to the tabs of the first positive electrode and the second positive electrode respectively.

[0058] The active material for both the first and second positive electrodes is LiMn2O4. In the initial state of the battery, the active material of the first positive electrode 1 is LiMn2O4, and the active material of the second positive electrode 5 is Li... 1-x Mn2O4, 0 < x < 1.

[0059] The solenoid valve has a common connection terminal and two positive connection terminals. The common connection terminal serves as the positive terminal outlet of the battery and is connected to an external charging and discharging circuit. The two positive connection terminals are connected to the first positive terminal and the second positive terminal, respectively. The solenoid valve switches its internal path to selectively connect the common connection terminal to one of the two positive terminals: initially, the common connection terminal is connected to the first positive terminal and disconnected from the second positive terminal; when the battery is charged to the cutoff voltage, the solenoid valve switches its path, disconnecting the common connection terminal from the first positive terminal and connecting it to the second positive terminal; then the discharge and charge cycle continues; after the next charge reaches the cutoff voltage, the solenoid valve switches again, connecting the common connection terminal to the first positive terminal and disconnecting it from the second positive terminal; this cycle repeats, and at the end of each charge, the solenoid valve switches its electrodes, disconnecting the current positive terminal and connecting the other set of positive terminals, achieving alternating single connection between the first and second positive terminals.

[0060] The preparation example and cycle performance test of the high-cycle-performance aqueous battery of the present invention are as follows:

[0061] Example 1: 1. LiMn2O4 was used as the positive electrode active material and mixed with SP, CNTs and PVDF in a mass ratio of 85:5:5:5, with a total solid weight of 65 parts. 35 parts of NMP were added according to the set solid content of 65% and stirred. During the stirring process, the viscosity of the slurry was monitored in real time. When the viscosity of the slurry reached 9000 mPa / s, the slurry was transferred to a coating machine and uniformly coated on one side of the Al foil current collector. Then, it was dried at 100℃, rolled, slit, and die-cut. Finally, the obtained LiMn2O4 electrode sheets were divided into two groups, A and B. 2. Using the LiMn2O4 electrode from group B as the positive electrode and excess activated carbon as the negative electrode, with N / P = 2, assemble a capacitor. Add 2M Li2SO4 as the electrolyte and charge the capacitor to complete the deLiization of the LiMn2O4 from group B. After charging is complete, the active material of the positive electrode of the capacitor will become Li. 1-x Mn2O4 was used to disassemble the capacitor and to analyze the Li-containing components. 1-x The Mn2O4 electrodes were cleaned and dried, and were designated as group C.

[0062] 3. This system is an aqueous lithium-ion battery system. Lithium titanium phosphate is selected as the negative electrode and is mixed with SP and PTFE in a mass ratio of 85:10:5, with a total solid weight of 27 parts. 33 parts of deionized water are added according to the set solid content of 45% and stirred. During the stirring process, the viscosity of the slurry is monitored in real time. When the viscosity of the slurry reaches 5500 mPa / s, the slurry is transferred to a coating machine and uniformly coated on both sides of the Cu foil current collector. Then, it is dried at 85℃, rolled, slit, and die-cut to finally obtain the negative electrode sheet.

[0063] 4. Setting the N / P ratio of the aqueous lithium-ion battery to 0.8, LiMn2O4 exhibits poor stability in aqueous batteries. An N / P ratio < 1 allows for shallow charging and discharging of the positive electrode, protecting the LiMn2O4 positive electrode and preventing excessive delithiation that could lead to structural collapse and failure of the LiMn2O4, thereby improving battery cycle performance. One positive electrode from group A and one from group C are selected, along with one negative electrode. The electrodes are assembled in the following order: "Group A positive electrode - separator - negative electrode - separator - Group C positive electrode," as shown in the diagram. Figure 1 As shown, group A is the first positive electrode 1, and group C is the second positive electrode 5. The side of group A and group C facing the negative electrode is a slurry coating layer. The electrolyte is 1M Li2SO4 + 2M LiOAc, and an aqueous lithium-ion battery is obtained through encapsulation and aging.

[0064] 5. Test the aqueous lithium-ion battery. Install a solenoid valve on the positive side. The solenoid valve is connected to the tabs of the A and C groups of electrodes to control the switching of the positive electrode. In the initial state, the solenoid valve is connected to the positive electrode of group A and disconnected from group C. The negative side is directly connected to the tab of the negative electrode. Set the required test steps to perform the test.

[0065] 6. The battery testing system first charges the positive and negative electrodes of group A in the aqueous lithium-ion battery system. The LiMn2O4 in the positive electrode of group A begins to degrade from Li. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group A undergoes Li degradation, transforming into Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group A and connecting to the positive electrode of group C. The battery then begins to discharge, and the Li-deionization of the positive electrode of group C... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group C... 1-x Mn2O4 is transformed into LiMn2O4 by Li intercalation.

[0066] 7. At this point, the path of the aqueous lithium-ion battery becomes the positive electrode || negative electrode of group C, and it enters the next charge-discharge cycle. The LiMn2O4 in the positive electrode of group C begins to deliquinate. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group C undergoes deliquescence to become Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group C and connecting to the positive electrode of group A. The battery then begins to discharge, and the Li-deionization of the positive electrode of group A... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group A... 1-x Mn2O4 is transformed into LiMn2O4 by Li intercalation.

[0067] 8. Then repeat the test steps 6-7 to perform subsequent cycle tests on the battery.

[0068] Comparative Example 1: Compared with Example 1, the aqueous lithium-ion battery in Comparative Example 1 has only one unde-Li-treated A-group electrode as the positive electrode, and the positive and negative electrode tabs are directly connected to the battery testing system during testing, without the need for switching of the control path by a solenoid valve. All other parameters are the same.

[0069] The cyclic stability curves of Example 1 and Comparative Example 1 are as follows: Figure 2 As shown, the battery internal resistance at different cycle numbers is compared to... Figure 3 As shown, the Mn content in the electrolyte at different cycle numbers 2+ Content for example Figure 4 As shown.

[0070] The results showed that the battery of the present invention retained more than 92.5% of its capacity after 1520 cycles, while the capacity of Comparative Example 1 decreased to 80% after 800 cycles, demonstrating a significant improvement in the cycle performance of the aqueous battery of the present invention. Furthermore, at the same number of cycles, the internal resistance of the battery of the present invention was significantly lower than that of Comparative Example 1, and the Mn content in the electrolyte was also lower. 2+ The content is about 30% of that in Comparative Example 1, which proves that the battery of the present invention significantly reduces the dissolution rate of the positive electrode material, improves the stability of the positive electrode material, thereby improving the battery cycle performance and extending the service life.

[0071] Example 2: 1. LiMn2O4 was used as the positive electrode active material and mixed with SP, carbon nanotubes, PVDF and polyamide in a mass ratio of 80:7:6:5:2, with a total solid weight of 42 parts. According to the set solid content of 60%, 22.4 parts of DMF and 5.6 parts of ethylene glycol were added and stirred. During the stirring process, the viscosity of the slurry was monitored in real time. When the viscosity of the slurry reached 7500 mPa / s, the slurry was transferred to a coating machine and uniformly coated on one side of the Al foil current collector. Then, it was dried at 95℃, rolled, slit and die-cut. Finally, the obtained LiMn2O4 electrode sheets were divided into two groups, A and B. 2. Using the LiMn2O4 electrode from group B as the positive electrode and excess activated carbon as the negative electrode, with N / P = 1.8, assemble a capacitor. Add 3M LiOAc as the electrolyte and charge the capacitor to complete the deLiization of the LiMn2O4 from group B. After charging is complete, the active material of the positive electrode of the capacitor will become Li. 1-x Mn2O4 was used to disassemble the capacitor and to analyze the Li-containing components. 1-x The Mn2O4 electrodes were cleaned and dried, and were designated as group C.

[0072] 3. This system is an aqueous lithium / sodium hybrid ion battery system. Sodium titanium phosphate is selected as the negative electrode and is mixed with SP, graphite, CMC and La136D in a mass ratio of 87:4:4:2:3, with a total solid weight of 22.5 parts. According to the set solid content of 45%, 19.25 parts of deionized water and 8.25 parts of ethanol are added and stirred. During the stirring process, the viscosity of the slurry is monitored in real time. When the viscosity of the slurry reaches 6800 mPa / s, the slurry is transferred to a coating machine and uniformly coated on both sides of the Al foil current collector. Then, it is dried at 80℃, rolled, slit and die-cut to finally obtain the negative electrode sheet.

[0073] 4. Set the N / P ratio of the aqueous lithium / sodium hybrid ion battery to 0.7. Select one positive electrode from group A and one from group C, and one negative electrode. Assemble the batteries in the order of "group A positive electrode - separator - negative electrode - separator - group C positive electrode". The side of the positive electrode facing the negative electrode is the slurry coating layer. The electrolyte is 2M LiOAc + 0.5M Na2SO4. After encapsulation and aging, the desired aqueous lithium / sodium hybrid ion battery is obtained.

[0074] 5. Test the aqueous lithium / sodium hybrid ion battery. Install a solenoid valve on the positive electrode side. The solenoid valve is connected to the tabs of the A and C groups of electrodes to control the switching of the positive electrode. In the initial state, the solenoid valve is connected to the positive electrode of group A and disconnected from group C. The negative electrode side is directly connected to the tab of the negative electrode. Set the required test steps to perform the test.

[0075] 6. The battery testing system first charges the positive and negative electrodes of group A in the aqueous lithium / sodium hybrid ion battery system. The LiMn2O4 in the positive electrode of group A begins to degrade Li. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group A undergoes Li degradation, transforming into Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group A and connecting to the positive electrode of group C. The battery then begins to discharge, and the Li-deionization of the positive electrode of group C... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group C... 1-x Mn2O4 is transformed into LiMn2O4 by Li intercalation.

[0076] 7. At this point, the path of the aqueous lithium / sodium hybrid ion battery becomes the positive electrode || negative electrode of group C, and it enters the next charge-discharge cycle. The LiMn2O4 in the positive electrode of group C begins to deliquinate. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group C undergoes deliquulation to become Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group C and connecting to the positive electrode of group A. The battery then begins to discharge, and the Li-deionization of the positive electrode of group A... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group A... 1-x Mn2O4 is transformed into LiMn2O4 by Li intercalation.

[0077] 8. Then repeat the test steps 6-7 to perform subsequent cycle tests on the battery.

[0078] Comparative Example 2: Compared with Example 2, the aqueous lithium / sodium hybrid ion battery in Comparative Example 2 has only one unde-Li-treated A-group electrode on the positive side, and the positive and negative electrode tabs are directly connected to the battery testing system during testing, without the need for switching of the solenoid valve control path. All other parameters are the same.

[0079] The cyclic stability curves of Example 2 and Comparative Example 2 are as follows: Figure 5 As shown, the battery internal resistance at different cycle numbers is compared to... Figure 6 As shown, the Mn content in the electrolyte at different cycle numbers 2+ Content for example Figure 7 As shown.

[0080] The results showed that Example 2 exhibited significantly improved cycle performance compared to Comparative Example 2. While Comparative Example 2's capacity decreased to 79.4% after 740 cycles, Example 2 maintained a capacity retention of over 80.5% after 2000 cycles. (The text also mentions battery internal resistance and Mn content in the electrolyte, but these appear unrelated to the main topic and are likely separate points.) 2+ The content results also showed that the content in Example 2 was significantly lower than that in Comparative Example 2.

[0081] Example 3: 1. LiMn2O4 was used as the positive electrode active material and mixed with acetylene black, graphene, PVDF and epoxy resin in a mass ratio of 90:5:1:2:2, with a total solid weight of 20 parts. 13 parts of NMP and 7 parts of dihydro-L-glucanone were added according to the set solid content of 50% and stirred. During the stirring process, the viscosity of the slurry was monitored in real time. When the viscosity of the slurry reached 8000 mPa / s, the slurry was transferred to a coating machine and uniformly coated on one side of the Ti foil current collector. Then, it was dried at 110 ℃, rolled, slit and die-cut. Finally, the obtained LiMn2O4 electrode sheets were divided into two groups, A and B. 2. Using the LiMn2O4 electrode from group B as the positive electrode and excess activated carbon as the negative electrode, with N / P = 2.3, assemble a capacitor. Add 2M LiOTF as the electrolyte and charge the capacitor to complete the deLiization of the LiMn2O4 from group B. After charging is complete, the active material of the positive electrode of the capacitor will become Li. 1-x Mn2O4 was used to disassemble the capacitor and to analyze the Li-containing components. 1-x The Mn2O4 electrodes were cleaned and dried, and were designated as group C.

[0082] 3. This system is an aqueous lithium-ion battery system. Activated carbon is selected as the negative electrode and is mixed with carbon nanotubes, Ketjen black, starch and SBR in a mass ratio of 82:1:10:2:5, with a total solid weight of 48 parts. According to the set solid content of 60%, 24 parts of deionized water and 8 parts of methyl pyruvate are added and stirred. During the stirring process, the viscosity of the slurry is monitored in real time. When the viscosity of the slurry reaches 7200 mPa / s, the slurry is transferred to a coating machine and uniformly coated on both sides of the Ti foil current collector. Then, it is dried at 75℃, rolled, slit and die-cut to finally obtain the negative electrode sheet.

[0083] 4. Set the N / P ratio of the aqueous lithium-ion battery to 0.6. Select one positive electrode from group A and one from group C, and one negative electrode. Assemble the batteries in the order of "group A positive electrode - separator - negative electrode - separator - group C positive electrode". Use 15M LiClO4 as the electrolyte. After encapsulation and aging, the desired aqueous lithium-ion battery is obtained.

[0084] 5. Test the aqueous lithium-ion battery. Install a solenoid valve on the positive side. The solenoid valve is connected to the tabs of the A and C groups of electrodes to control the switching of the positive electrode. In the initial state, the solenoid valve is connected to the positive electrode of group A and disconnected from group C. The negative side is directly connected to the tab of the negative electrode. Set the required test steps to perform the test.

[0085] 6. The battery testing system first charges the positive and negative electrodes of group A in the aqueous lithium-ion battery system. The LiMn2O4 in the positive electrode of group A begins to degrade from Li. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group A undergoes Li degradation, transforming into Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group A and connecting to the positive electrode of group C. The battery then begins to discharge, and the Li-deionization of the positive electrode of group C... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group C... 1-x Mn2O4 is transformed into LiMn2O4 by Li intercalation.

[0086] 7. At this point, the path of the aqueous lithium-ion battery becomes the positive electrode || negative electrode of group C, and it enters the next charge-discharge cycle. The LiMn2O4 in the positive electrode of group C begins to deliquinate. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group C undergoes deliquescence to become Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group C and connecting to the positive electrode of group A. The battery then begins to discharge, and the Li-deionization of the positive electrode of group A... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group A... 1-xMn2O4 is transformed into LiMn2O4 by Li intercalation.

[0087] 8. Then repeat the test steps 6-7 to perform subsequent cycle tests on the battery.

[0088] Comparative Example 3: Compared with Example 3, the aqueous lithium-ion battery in Comparative Example 3 only has one unde-Li-treated A-group electrode as the positive electrode, and the positive and negative electrodes are directly connected to the battery testing system during testing, without the need for switching of the control path by a solenoid valve. All other parameters are the same.

[0089] The cyclic stability curves of Example 3 and Comparative Example 3 are as follows: Figure 8 As shown.

[0090] The results show that the battery of the present invention retains about 62% of its capacity after 800 cycles, while the comparative example 3 retains only about 40% of its capacity after 190 cycles. The cycling performance of the aqueous battery of the present invention is significantly improved.

[0091] Example 4: 1. LiMn2O4 was used as the positive electrode active material and mixed with SP, graphene, polyurethane and phenolic resin in a mass ratio of 75:13:5:3:4, with a total solid weight of 27.5 parts. 13.5 parts of isopropanol and 9 parts of ethyl acetate were added according to the set solid content of 55% and stirred. During the stirring process, the viscosity of the slurry was monitored in real time. When the viscosity of the slurry reached 7000 mPa / s, the slurry was transferred to a coating machine and uniformly coated on one side of a stainless steel foil current collector. Then, it was dried at 90 ℃, rolled, slit and die-cut. Finally, the obtained LiMn2O4 electrode sheets were divided into two groups, A and B. 2. Using the LiMn2O4 electrode from group B as the positive electrode and excess activated carbon as the negative electrode, with N / P = 1.6, assemble a capacitor. Add 4M LiNO3 as the electrolyte and charge the capacitor to complete the deLiization of the LiMn2O4 from group B. After charging is complete, the active material of the positive electrode of the capacitor will become Li. 1-x Mn2O4 was used to disassemble the capacitor and to analyze the Li-containing components. 1-x The Mn2O4 electrodes were cleaned and dried, and were designated as group C.

[0092] 3. This system is an aqueous lithium-ion battery system. Titanium dioxide is selected as the negative electrode and is mixed with activated carbon, carbon fiber, Na-based bentonite, and rosin in a mass ratio of 90:2:2:4.5:1.5, with a total solid weight of 22 parts. According to the set solid content of 40%, 26.4 parts of isopropanol and 6.6 parts of methyl formate are added and stirred. During the stirring process, the viscosity of the slurry is monitored in real time. When the viscosity of the slurry reaches 5000 mPa / s, the slurry is transferred to a coating machine and uniformly coated on both sides of the graphite paper current collector. Then, it is dried at 65 ℃, rolled, slit, and die-cut to finally obtain the negative electrode sheet.

[0093] 4. Set the N / P ratio of the aqueous lithium-ion battery to 0.5. Select one positive electrode from group A and one from group C, and one negative electrode. Assemble the battery in the order of "group A positive electrode - separator - negative electrode - separator - group C positive electrode". Use 4M LiOAc + 1M LiTFSI as the electrolyte. After encapsulation and aging, the desired aqueous lithium-ion battery is obtained.

[0094] 5. Test the aqueous lithium-ion battery. Install a solenoid valve on the positive side. The solenoid valve is connected to the tabs of the A and C groups of electrodes to control the switching of the positive electrode. In the initial state, the solenoid valve is connected to the positive electrode of group A and disconnected from group C. The negative side is directly connected to the tab of the negative electrode. Set the required test steps to perform the test.

[0095] 6. The battery testing system first charges the positive and negative electrodes of group A in the aqueous lithium-ion battery system. The LiMn2O4 in the positive electrode of group A begins to degrade from Li. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group A undergoes Li degradation, transforming into Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group A and connecting to the positive electrode of group C. The battery then begins to discharge, and the Li-deionization of the positive electrode of group C... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group C... 1-x Mn2O4 is transformed into LiMn2O4 by Li intercalation.

[0096] 7. At this point, the path of the aqueous lithium-ion battery becomes the positive electrode || negative electrode of group C, and it enters the next charge-discharge cycle. The LiMn2O4 in the positive electrode of group C begins to deliquinate. When the voltage reaches the set charging cutoff voltage, the LiMn2O4 in the positive electrode of group C undergoes deliquescence to become Li. 1-x Mn2O4, at this point, the solenoid valve switches its path, disconnecting from the positive electrode of group C and connecting to the positive electrode of group A. The battery then begins to discharge, and the Li-deionization of the positive electrode of group A... 1-x Mn₂O₄ begins to intercalate Li. Once the voltage reaches the set discharge cutoff voltage, the Li at the positive electrode of group A... 1-xMn2O4 is transformed into LiMn2O4 by Li intercalation.

[0097] 8. Then repeat the test steps 6-7 to perform subsequent cycle tests on the battery.

[0098] Comparative Example 4: Compared with Example 4, the positive electrode of the aqueous lithium-ion battery in Comparative Example 4 only has one unde-Li-treated A-group electrode as the positive electrode, and the positive and negative electrode tabs are directly connected to the battery testing system during testing, without the need for switching of the control path by the solenoid valve. All other parameters are the same.

[0099] The cyclic stability curves of Example 4 and Comparative Example 4 are as follows: Figure 9 As shown.

[0100] The results showed that the battery of the present invention retained 88.4% of its capacity after 625 cycles, while the capacity retention of Comparative Example 4 was 81.5% after 200 cycles, indicating that the cycle performance of the aqueous battery of the present invention is significantly improved.

Claims

1. A high-cycle-performance aqueous battery, characterized in that, The battery includes an aqueous electrolyte, a negative electrode, a first positive electrode and a second positive electrode located on both sides of the negative electrode, and a first diaphragm and a second diaphragm respectively provided between the first positive electrode and the negative electrode and between the second positive electrode and the negative electrode; the battery is equipped with a solenoid valve, which is electrically connected to the first positive electrode and the second positive electrode respectively, and controls the switching of the positive electrode in the charging and discharging circuit, so that the first positive electrode and the second positive electrode are alternately connected to the charging and discharging circuit.

2. The high-cycle-performance aqueous battery as described in claim 1, characterized in that, The active materials for both the first and second positive electrodes are lithium manganese oxide. In the initial state of the battery, the active material for the first positive electrode is LiMn₂O₄, and the active material for the second positive electrode is Li₂O₄. 1-x Mn2O4, 0 < x < 1.

3. The high-cycle-performance aqueous battery as described in claim 1, characterized in that, The N / P ratio of the negative electrode to the first positive electrode or the second positive electrode satisfies the condition 0.4 ≤ N / P ratio < 1.

4. The high-cycle-performance aqueous battery as described in claim 1, characterized in that, The first positive electrode and the second positive electrode are respectively provided with tabs, and the solenoid valve is electrically connected to the tabs of the first positive electrode and the second positive electrode respectively.

5. The high-cycle-performance aqueous battery as described in claim 1, characterized in that, After each discharge and charge cycle is completed, the solenoid valve switches the electrode connection relationship: when charging is finished, the solenoid valve switches the electrodes, disconnects the connection with the current positive electrode and connects to another set of positive electrodes, and alternately connects the first positive electrode and the second positive electrode to the charging and discharging circuit.

6. The high-cycle-performance aqueous battery as described in claim 5, characterized in that, The charging and discharging process of the aqueous battery is as follows: (i) Initial charging In the initial state, the solenoid valve connects the first positive terminal and disconnects the second positive terminal, and the charging circuit is the first positive terminal to the negative terminal. Charging is started until the voltage reaches the preset charging cut-off voltage, and charging ends. (ii) First discharge After charging is completed, the solenoid valve switches the circuit, disconnecting the first positive terminal and connecting the second positive terminal. The discharge circuit is switched to the second positive terminal-negative terminal, and the discharge is started until the voltage reaches the preset discharge cutoff voltage, at which point the discharge ends. (iii) Cyclic charging and discharging After the discharge is completed, the battery maintains the second positive-negative circuit for the next round of charging until the voltage reaches the preset charging cutoff voltage. Then, the solenoid valve switches the circuit again, disconnecting the second positive terminal and reconnecting the first positive terminal to start a new round of discharge. Repeat the above discharge, charge, and solenoid valve switching steps to achieve battery cycle operation.

7. The high-cycle-performance aqueous battery as described in claim 1, characterized in that, Both the first positive electrode and the second positive electrode include a positive electrode current collector and a positive electrode active layer. The positive electrode active layer includes a positive electrode active material, a positive electrode binder, and a positive electrode conductive agent. The positive electrode active layer is disposed on one side of the positive electrode current collector. The negative electrode includes a negative electrode current collector and a negative electrode active layer, which are disposed on both sides of the negative electrode current collector; the negative electrode active layer includes a negative electrode active material, a negative electrode binder, and a negative electrode conductive agent.

8. The high-cycle-performance aqueous battery as described in claim 7, characterized in that, The negative electrode active material is one of lithium titanium phosphate, sodium titanium phosphate, titanium dioxide, and activated carbon. The positive electrode active material of the first positive electrode is LiMn2O4; the positive electrode active material of the second positive electrode is Li 1-x Mn2O4; The electrolyte is an aqueous solution of lithium salt and / or sodium salt with a concentration of 0.5-18 mol / L.

9. The method for preparing a high-cycle-performance aqueous battery according to any one of claims 1 to 8, characterized in that, The method includes the following steps: (1) The positive electrode active material, positive electrode binder, and positive electrode conductive agent are mixed, and a solvent is added to prepare a positive electrode slurry. This slurry is coated on one side of the positive electrode current collector and dried to obtain a positive electrode sheet. The positive electrode active material is LiMn2O4, thus obtaining the first positive electrode. The positive electrode active material is Li 1-x Mn2O4 was used to prepare the second cathode, where 0 < x < 1; (2) The negative electrode active material, negative electrode conductive agent and negative electrode binder are mixed, and a solvent is added to make a negative electrode slurry. The slurry is coated on both sides of the negative electrode current collector and dried to obtain the negative electrode. (3) Assemble the first positive electrode, the first diaphragm, the negative electrode, the second diaphragm, and the second positive electrode in that order. The side of the first positive electrode and the second positive electrode coated with the positive electrode slurry faces the negative electrode side respectively. Inject electrolyte, encapsulate, and set up a solenoid valve at the positive electrode position. Connect the solenoid valve to the first positive electrode and the second positive electrode respectively to control the switching of the positive electrode and obtain an aqueous battery.

10. The method as described in claim 9, characterized in that, The N / P ratio of the negative electrode to the first positive electrode or the second positive electrode satisfies the condition 0.4 ≤ N / P ratio < 1.

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