A method of forming a high capacity liquid metal battery

Abstract

The present application relates to the technical field of liquid metal battery, and particularly relates to a formation method of large-capacity liquid metal battery. The formation method of large-capacity liquid metal battery is characterized in that, from the first cycle, deep charge and discharge at a low rate is carried out to preliminarily build a relatively stable electrode / electrolyte interface, and at the same time, the positive active material is used to the maximum extent; then the discharge rate is appropriately increased, and shallow charge and shallow discharge at the same discharge depth are carried out to gradually consolidate the stable electrode / electrolyte interface and activate the positive active material, so that the positive active material is fully utilized, and finally, the battery formation is completed. In addition, an optimization method combining a series of means such as increasing the discharge rate, reducing the discharge depth, reducing the cycle number, and increasing the activation temperature is proposed for the elements affecting the duration and quality of the formation of the large-capacity liquid metal battery, the boundary conditions of the high-quality formation of the large-capacity liquid metal battery are explored, and the duration of the battery formation is shortened as much as possible, and the formation efficiency is improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of liquid metal battery, and in particular to a formation method of large-capacity liquid metal battery. BACKGROUND

[0002] At present, the research on liquid metal battery is becoming mature, and it is about to enter the industrialization stage. Similar to most battery systems, the battery needs to have an activation process, i.e. a formation process, before use. The battery after formation can maintain a stable state of high coulomb efficiency, full capacity charging and discharging. The difference is that due to the large capacity (200-500 Ah) of the liquid metal battery, the thick electrode and electrolyte material, and the large reaction interface area, etc., the battery will have problems such as low mass transfer efficiency, uneven current density distribution, unstable electrode / electrolyte interface, and low utilization rate of active material during the initial charging and discharging process. Therefore, the battery needs a long activation process to build a stable electrode / electrolyte interface and achieve stable and efficient mass transfer and active material utilization. During the activation stage of the battery, the high-rate charging and discharging mode will exacerbate the uneven distribution of current density in the battery, and the rapid enrichment of the melt in the area with high current density will easily cause short circuit of the battery. Therefore, the current formation process commonly used for large-capacity battery cells is a constant current charging and discharging mode from shallow (20-30%) to deep (60-80% DOD) at low rate (generally 0.05-0.1C) to gradually build a stable electrode / electrolyte interface (see CN106981691B for details A large-capacity liquid metal battery interface formation method). Although this progressive formation process can activate the large-capacity battery, the activation period of the battery is too long, generally 1-2 weeks, and the activation efficiency is low. For industrial production, the production cost is high and the production efficiency is low. Therefore, it is urgent to develop a rapid and efficient formation method for large-capacity liquid metal batteries to reduce costs and increase efficiency. SUMMARY

[0003] The purpose of the present application is to provide a formation method of large-capacity liquid metal battery to solve the above problems in the prior art.

[0004] The formation method of large-capacity liquid metal battery provided by the present application comprises the following steps:

[0005] S1, placing the large-capacity liquid metal battery in a test furnace and connecting a test instrument, and heating to a working temperature;

[0006] S2, after the large-capacity liquid metal battery is heated to the working temperature, the voltage change of the large-capacity liquid metal battery is detected by opening the test program, and after the voltage of the large-capacity liquid metal battery is normal and the fluctuation is small, the large-capacity liquid metal battery is placed for a predetermined time;

[0007] S3, small rate constant current discharge the large capacity liquid metal battery to the cut-off voltage, make the discharge depth of the large capacity liquid metal battery 80% DOD-100% DOD;

[0008] S4, after the large capacity liquid metal battery is placed for 5-30 min, small rate or medium rate constant current charging is carried out to the cut-off voltage of the large capacity liquid metal battery;

[0009] After the large capacity liquid metal battery is placed for 5-30 min, small rate or medium rate constant current discharge is carried out to the large capacity liquid metal battery, and the discharge time is controlled, so that the discharge depth of the large capacity liquid metal battery is 20% DOD-80% DOD;

[0010] Wherein, after step S4 is carried out for 0-6 times, if the coulomb efficiency of the large capacity liquid metal battery is less than 95%, the following steps S5-S7 are continued; if the coulomb efficiency of the large capacity liquid metal battery is greater than or equal to 95%, the battery activation is completed, and the following steps S5-S7 do not need to be carried out;

[0011] S5, after the large capacity liquid metal battery is placed for 5-30 min, small rate or medium rate constant current charging is carried out to the cut-off voltage of the large capacity liquid metal battery;

[0012] After the large capacity liquid metal battery is placed for 5-30 min, small rate or medium rate constant current discharge is carried out to the large capacity liquid metal battery, and the discharge time is controlled, so that the discharge depth of the large capacity liquid metal battery is 20% DOD-80% DOD;

[0013] S6, after the large capacity liquid metal battery is placed for 5-30 min, small rate or medium rate constant current charging is carried out to the cut-off voltage of the large capacity liquid metal battery;

[0014] After the large capacity liquid metal battery is placed for 5-30 min, small rate or medium rate constant current discharge is carried out to the large capacity liquid metal battery, and the discharge time is controlled, so that the discharge depth of the large capacity liquid metal battery is 20% DOD-80% DOD;

[0015] S7, repeat step S6 until the coulomb efficiency of the large capacity liquid metal battery is greater than or equal to 95%, and the battery activation is completed.

[0016] Further, when the large capacity liquid metal battery is charged and discharged, the small rate is 0.05-0.15C, and the medium rate is 0.15-0.5C.

[0017] Further, when the large capacity liquid metal battery is charged and discharged, the small rate is 0.1C, and the medium rate is 0.2C.

[0018] Further, step S2 is scheduled for 2h.

[0019] Further, step S4 is performed twice before step S5 is performed.

[0020] Further, in step S7, the number of times of repeating step S6 is 0-6.

[0021] Further, in step S4, the depth of discharge is 40% DOD-75% DOD.

[0022] Further, the total time of formation is no more than 80h.

[0023] The present application is contrary to the design concept of the current progressive formation method of large-capacity liquid metal batteries. The formation method of the large-capacity liquid metal battery of the present application performs deep charge and discharge at a low rate from the first cycle to preliminarily build a relatively stable electrode / electrolyte interface, while maximizing the use of the positive active material. Subsequently, the discharge rate is appropriately increased, and shallow charge and shallow discharge are performed at the same discharge depth to gradually consolidate the stable electrode / electrolyte interface and activate the positive active material, so that the positive active material is fully utilized, and the battery formation is finally completed. In addition, the optimization method combining a series of means such as increasing the discharge rate, reducing the discharge depth, reducing the cycle number, and increasing the activation temperature is proposed for the elements affecting the duration and quality of the formation of the large-capacity liquid metal battery, the boundary conditions of the high-quality formation of the large-capacity liquid metal battery are explored, and the duration of the battery formation is shortened as much as possible to improve the formation efficiency.

[0024] The formation method of the large-capacity liquid metal battery provided by the present application mainly has the following beneficial effects:

[0025] (1) The performance of the large-capacity liquid metal battery formed by the method of the present application is excellent. After the formation is completed, the battery is tested by full charge and full discharge cycles at 0.2C rate, and the coulombic efficiency of each cycle of the battery is maintained at more than 98%, and the optimal coulombic efficiency can be maintained at more than 99% for stable operation, and the formation quality is high and efficient.

[0026] (2) The formation time of the large-capacity liquid metal battery formed by the method of the present application is shortened to 2 days (46h). Compared with the general large-capacity liquid metal battery formation method, the formation time is shortened by at least 62-86%, which greatly improves the formation efficiency and reduces the formation cost.

[0027] (3) The low rate and deep charge and discharge mode is used in the first cycle of the battery operation, which can preliminarily build a relatively stable electrode / electrolyte interface, and can maximize the activation of the positive active material to participate in the electrochemical reaction, improve the activation quality, and effectively avoid the short circuit failure of the battery.

[0028] (4) The first circle of charge and discharge, the battery reaction interface has been initially formed, at this time, the shallow charge and discharge mode is entered, which can consolidate the formed electrode / electrolyte interface and gradually complete the activation of a small amount of remaining positive active material, while reducing the activation time.

[0029] (5) The optimization method combining a series of means such as increasing the discharge rate, reducing the discharge depth, reducing the cycle number, and increasing the activation temperature is proposed, and the efficient activation of the large-capacity liquid metal battery is realized. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 is a flowchart of the formation method of the large-capacity liquid metal battery provided by the present application;

[0031] Figure 2 、 3 , 4, 5 are flowcharts of the formation method of the large-capacity liquid metal battery corresponding to examples 1, 2, 3, and 4, respectively;

[0032] Figure 6 is a comparison chart of the benefits achieved by the formation method of the large-capacity liquid metal battery of the present application and the benefits achieved by the formation method of the large-capacity liquid metal battery provided by Chinese patent CN106981691B. DETAILED DESCRIPTION

[0033] The following is a specific embodiment of the present application combined with the drawings, which further describes the technical solutions of the present application, but the present application is not limited to these embodiments.

[0034] Figure 1 is a flowchart of the formation method of the large-capacity liquid metal battery provided by the present application.

[0035] Table 1 lists four embodiments of the present application, each of which includes 2-4 specific implementation cases of 200Ah batteries.

[0036] Example 1

[0037] As shown in Figure 2 , this embodiment uses liquid metal batteries with a capacity of 200Ah (referred to as No. 1, 2, 3, and 4 batteries), and the formation method mainly includes the following steps:

[0038] (1) Place No. 1, 2, 3, and 4 batteries in four heating furnaces, respectively, and heat No. 1, 2, 3, and 4 batteries to the working temperature at a heating rate of 4℃ / min.

[0039] (2) When the temperature of No. 1, 2, 3, and 4 batteries reaches the working temperature, open the battery test program, detect the voltage of No. 1, 2, 3, and 4 batteries, and after the voltage of No. 1, 2, 3, and 4 batteries is stable, set aside for 2h.

[0040] (3) Constant current discharge of Nos. 1, 2, 3, 4 batteries at a discharge rate of 0.1C (20A) while controlling the discharge cut-off voltage so that the discharge depth of Nos. 1, 2, 3, 4 batteries is 100% DOD.

[0041] (4) After resting Nos. 1, 2, 3, 4 batteries for 10 min, constant current charging of Nos. 1, 2, 3, 4 batteries to full charge at a charge rate of 0.1C (20A).

[0042] (5) After resting Nos. 1, 2, 3, 4 batteries for 10 min, constant current discharge of Nos. 1, 2, 3, 4 batteries at a discharge rate of 0.1C (20A) while controlling the discharge time to 450 min (7.5h) so that the discharge depth of Nos. 1, 2, 3, 4 batteries is 75% DOD.

[0043] (6) After resting Nos. 1, 2, 3, 4 batteries for 10 min, constant current charging of Nos. 1, 2, 3, 4 batteries to cut-off voltage at a charge rate of 0.1C (20A).

[0044] (7) Go to Step (5) and repeat for 4 cycles.

[0045] (8) Constant current discharge of Nos. 1, 2, 3, 4 batteries at a discharge rate of 0.2C (40A) while controlling the discharge cut-off voltage so that the discharge depth of Nos. 1, 2, 3, 4 batteries is 100% DOD.

[0046] (9) After resting Nos. 1, 2, 3, 4 batteries for 10 min, constant current charging of Nos. 1, 2, 3, 4 batteries to cut-off voltage at a charge rate of 0.2C (40A).

[0047] (10) After resting Nos. 1, 2, 3, 4 batteries for 10 min, constant current discharge of Nos. 1, 2, 3, 4 batteries at a discharge rate of 0.2C (40A) while controlling the discharge time to 225 min (3.75h) so that the discharge depth of Nos. 1, 2, 3, 4 batteries is 75% DOD.

[0048] (11) After resting Nos. 1, 2, 3, 4 batteries for 10 min, constant current charging of Nos. 1, 2, 3, 4 batteries to cut-off voltage at a charge rate of 0.2C (40A).

[0049] (12) Go to Step (10) and repeat for 4 cycles until the coulombic efficiency of Nos. 1, 2, 3, 4 batteries is greater than or equal to 95% and the battery formation is completed.

[0050] The formation time was 79 hours.

[0051] Verify the formation quality and stability of the formed battery:

[0052] (13) After batteries 1, 2, 3, and 4 are left standing for 10 minutes, they are discharged at a constant current with a discharge rate of 0.2C (40A). At the same time, the discharge cut-off voltage is controlled so that the depth of discharge of batteries 1, 2, 3, and 4 is 100% DOD.

[0053] (14) After batteries 1, 2, 3, and 4 are left standing for 10 minutes, they are charged with a constant current to the cut-off voltage at a charging rate of 0.2C (40A).

[0054] (15) Go to step (13) and cycle for 3 cycles. Record the discharge capacity and coulomb efficiency of the battery in each cycle as a verification standard for whether the battery is qualified.

[0055] Table 2 shows the specific parameters of batteries No. 1, 2, 3, and 4 after they were formed. The batteries were charged and discharged for three cycles at 0.2C (40A). This further verifies the formation quality and stability of the formed batteries.

[0056] Example 2

[0057] like Figure 3 As shown, this embodiment uses a liquid metal battery with a capacity of 200Ah (denoted as No. 5 and No. 6 batteries). The main steps of the formation method are similar to those of Example 1, except that the discharge depth is reduced and the number of cycles is reduced in steps (5)-(7), and the discharge depth is reduced in steps (10)-(12). The specific parameters are shown in Example 2 in Table 1.

[0058] The formation time is 60 hours.

[0059] Table 3 shows the specific parameters of No. 5 and No. 6 batteries after formation. The batteries were charged and discharged for three cycles at 0.2C (40A). This further verifies the formation quality and stability of the formed batteries.

[0060] Example 3

[0061] like Figure 4 As shown, this embodiment uses a liquid metal battery with a capacity of 200Ah (denoted as batteries 7, 8, 9, and 10). The main steps of the formation method are similar to those of Example 1, except that steps (5) to (7) are omitted, and the depth of discharge is reduced in steps (10) to (12). The specific parameters are shown in Example 3 in Table 1.

[0062] The formation time is 50 hours.

[0063] Table 4 shows the specific parameters of the 7, 8, 9, 10 batteries after formation, and the batteries are subjected to 3 cycles of charge and discharge at 0.2C (40A), which further verifies the formation quality and stability of the formed batteries.

[0064] Example 4

[0065] As shown in Table 1, Example 3, this embodiment uses liquid metal batteries with a capacity of 200 Ah (referred to as batteries 7, 8, 9, 10), and the main steps of the formation method are similar to those of Example 1. The difference is that steps (5)-(7) are not used, and in steps (10)-(12), the depth of discharge is reduced. The specific parameters are shown in Table 1, Example 3. Figure 5 The formation time is 46 hours.

[0066] Table 5 shows the specific parameters of the 11, 12, 13, 14 batteries after formation, and the batteries are subjected to 3 cycles of charge and discharge at 0.2C (40A), which further verifies the formation quality and stability of the formed batteries.

[0067] Table 1

[0068]

[0069]

[0070] Table 2 Table 3 Table 4

[0071]

[0072] Table 5

[0073]

[0074] As can be seen from Tables 2-5, the Coulomb efficiency of the batteries obtained by the formation method of the present application is more than 98%.

[0075] Figure 6 is the benefit obtained by the formation method of the large-capacity liquid metal battery of the present application compared with the benefit obtained by the formation method of the large-capacity liquid metal battery provided by Chinese patent CN106981691B. As can be seen from the figure, the formation time used by the formation method of the present application is less, and the Coulomb efficiency of the obtained battery is high.

[0076] The above does not involve the prior art.

[0077] ​Although some specific embodiments of the present application have been described in detail by way of example with reference to the drawings, it is to be understood that the above examples are intended to be illustrative only and are not intended to limit the scope of the present application, and that various modifications and changes can be made by those skilled in the art to the particular embodiments described without departing from the spirit and scope of the present application. It is intended that the scope of the present application be limited only by the broadest interpretation of the appended claims to be accorded under 35 U.S.C. § 112.

Claims

1. A formation method for a large-capacity liquid metal battery, characterized in that: The following steps are involved: S1. Place the large-capacity liquid metal battery in a test furnace, connect the test instrument, and heat it to the operating temperature. S2. After the large-capacity liquid metal battery is heated to the operating temperature, a test program is started to detect the voltage change of the large-capacity liquid metal battery. After the voltage of the large-capacity liquid metal battery is normal and the fluctuation is small, the test is left for a predetermined time; S3, performing a small rate constant current discharge on the large-capacity liquid metal battery to a cut-off voltage, so that the discharge depth of the large-capacity liquid metal battery is 80% DOD to 100% DOD; S4, after the large-capacity liquid metal battery is left for 5 to 30 minutes, the large-capacity liquid metal battery is charged at a small rate or a medium rate constant current to a cut-off voltage; After the large-capacity liquid metal battery is left for 5 to 30 minutes, the large-capacity liquid metal battery is discharged at a small rate or a medium rate constant current, and the discharge time is controlled so that the discharge depth of the large-capacity liquid metal battery is 20% DOD to 80% DOD; Wherein, after step S4 is performed 0-6 times, if the coulombic efficiency of the large-capacity liquid metal battery is less than 95%, proceed to the following steps S5 to S7; if the coulombic efficiency of the large-capacity liquid metal battery is greater than or equal to 95%, the battery activation is completed and the following steps S5 to S7 are no longer required; S5, after the large-capacity liquid metal battery is left for 5 to 30 minutes, the large-capacity liquid metal battery is charged at a small rate or a medium rate constant current to a cut-off voltage; After the large-capacity liquid metal battery is left for 5 to 30 minutes, the large-capacity liquid metal battery is discharged at a small rate or a medium rate constant current to a cut-off voltage, so that the discharge depth of the large-capacity liquid metal battery is 80% DOD to 100% DOD; S6. After the large-capacity liquid metal battery is left for 5 to 30 minutes, the large-capacity liquid metal battery is charged at a small rate or a medium rate constant current to a cut-off voltage; After the large-capacity liquid metal battery is left for 5 to 30 minutes, the large-capacity liquid metal battery is discharged at a small rate or a medium rate constant current, and the discharge time is controlled so that the discharge depth of the large-capacity liquid metal battery is 20% DOD to 80% DOD; S7, repeat step S6 until the coulombic efficiency of the large-capacity liquid metal battery is greater than or equal to 95%, and the battery activation is completed; When the large-capacity liquid metal battery is charged and discharged, the small rate is 0.05-0.15C, and the medium rate is 0.15-0.5C.

2. The formation method of a large-capacity liquid metal battery according to claim 1, characterized in that: When the large-capacity liquid metal battery is charged and discharged, the small rate is 0.1C and the medium rate is 0.2C.

3. The formation method of a large-capacity liquid metal battery according to claim 1, characterized in that: The scheduled time for step S2 is 2 hours.

4. The formation method of a large-capacity liquid metal battery according to claim 1, characterized in that: Step S4 is performed twice before step S5 is performed.

5. The formation method of a large-capacity liquid metal battery according to claim 1, characterized in that: In step S7, step S6 is repeated 0 to 6 times.

6. The formation method of a large-capacity liquid metal battery according to claim 1, characterized in that: In step S4, the depth of discharge is 40% DOD to 75% DOD.

7. The formation method of a large-capacity liquid metal battery according to claim 1, characterized in that: The total formation time shall not exceed 80h.

Images