Battery charging and discharging method and electronic equipment

Abstract

The invention relates to the technical field of sodium ion batteries, in particular to a battery charging and discharging method and electronic equipment. The method comprises the following steps: acquiring charging and discharging working condition information and environment temperature of the sodium-ion battery; the charging and discharging condition information and the environment temperature of the sodium ion battery are judged; when the sodium ion battery is in a discharge working condition and the environment temperature is 1t; when a temperature threshold value is preset, constant-current discharging is carried out until the cut-off voltage Vd1 is 0V; carrying out constant-current discharge to cut-off voltage Vd2 when the environment temperature is not less than a preset temperature threshold value in a discharge working condition; in a charging working condition, the temperature environment is tilt; when a temperature threshold value is preset, constant-current charging is carried out until the cut-off voltage is Vc1; and carrying out constant-current and constant-voltage charging in a charging working condition when the environment temperature is greater than or equal to a preset temperature threshold value. According to the method, different charging and discharging strategies are provided according to different charging and discharging working conditions and environment temperatures, so that the low-temperature charging and discharging cycle performance of the sodium ion battery can be improved, and the method is low in cost and easy to implement.

Description

Technical Field

[0001] The present invention relates to the technical field of sodium ion batteries, and in particular to a battery charging and discharging method and electronic equipment. Background Art

[0002] In the context of the current global energy transformation and the rapid popularization of new energy vehicles, there is a growing demand for efficient and environmentally friendly energy storage systems. Battery technology, especially lithium-ion batteries (LIBs), has become the mainstream choice for secondary batteries due to their high energy density and good cycle stability. However, the performance of batteries in low temperature environments has become a key factor restricting their further application, especially under extreme climate conditions, where the battery's charge and discharge performance is significantly reduced.

[0003] As an emerging secondary battery technology, sodium-ion batteries (SIBs) are considered to be a potential alternative technology due to their abundant raw materials, low cost, and similar working principles to LIBs. Compared with lithium-ion batteries, sodium-ion batteries have certain advantages in low-temperature environments, mainly due to the smaller Stokes diameter of sodium ions, which helps to improve their mobility in the electrolyte, thereby maintaining good electrochemical performance under low temperature conditions. However, the performance improvement of sodium-ion batteries in low-temperature environments still faces challenges, including severe attenuation of discharge capacity and difficulty in charging, which is mainly due to the inhibition of sodium ion diffusion at low temperatures, the decrease in electrolyte conductivity, and the competition between sodium ion embedding and sodium plating reactions on the negative electrode.

[0004] At present, there are two main methods to improve the low-temperature performance of batteries: one is to add an external heating device to heat the battery to a suitable operating temperature through an external heat source to improve its charge and discharge performance; the other is to improve the active materials and electrolytes in the battery from the material itself. However, the above methods will increase costs and are difficult.

[0005] Therefore, it is of great significance to provide a low-cost solution to the low-temperature performance and cycle performance of sodium-ion batteries.

[0006] In view of this, the present invention is proposed. Summary of the invention

[0007] The first purpose of the present invention is to provide a battery charging and discharging method, which can improve the low-temperature charging and discharging cycle performance of sodium ion batteries by proposing different charging and discharging strategies for different charging and discharging conditions and battery working environment temperatures. The method is low-cost and easy to implement. It not only solves the problem of severe capacity attenuation of sodium ion batteries at low temperatures, but also solves the problem of high cost and difficulty of existing methods for improving battery low-temperature performance.

[0008] A second object of the present invention is to provide an electronic device.

[0009] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0010] The present invention first provides a battery charging and discharging method, comprising the following steps:

[0011] Obtain the charging and discharging condition information and ambient temperature of the sodium ion battery;

[0012] Determining the charging and discharging condition information of the sodium ion battery and the ambient temperature;

[0013] When the sodium ion battery is in a discharge condition and the ambient temperature is lower than a preset temperature threshold, a constant current discharge is performed and the battery is discharged to a cut-off voltage V d1 When the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, a constant current discharge is performed and the battery is discharged to a cut-off voltage V d2 ;

[0014] When the sodium ion battery is in a charging condition and the temperature environment is lower than the preset temperature threshold, constant current charging is performed and charged to a cut-off voltage of V c1 ; When the sodium ion battery is in a charging condition and the ambient temperature is greater than or equal to a preset temperature threshold, constant current and constant voltage charging is performed;

[0015] The V d1 is 0V.

[0016] Furthermore, the preset temperature threshold is 25°C.

[0017] Furthermore, when the sodium ion battery is in a discharging condition and the ambient temperature is lower than a preset temperature threshold, the discharge current I of the constant current discharge is d1 Satisfy 0.1C≤I d1 ≤3C.

[0018] Furthermore, when the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, the constant current discharge is performed to a discharge cut-off voltage V d2 0~4V.

[0019] Furthermore, when the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, the discharge current I of the constant current discharge is d2 Satisfy 0.1C≤I d2 ≤6C.

[0020] Furthermore, when the sodium ion battery is in a charging condition and the temperature environment is lower than a preset temperature threshold, the constant current charging is performed until the cut-off voltage V c1 2~4V.

[0021] Furthermore, the V c1 It is 2~3.7V.

[0022] Furthermore, when the sodium ion battery is in a charging condition and the temperature environment is lower than a preset temperature threshold, the charging current I c1 Satisfy 0.01C≤I c1 ≤1C.

[0023] Furthermore, the constant current constant voltage charging comprises: firstly charging the sodium ion battery with a charging current of I c2 Perform constant current charging until the charging cut-off voltage is V c2 , then with the V c2 Constant voltage charging until the current drops to 0.05I c2 Stop charging when

[0024] Furthermore, the I c2 Satisfy 0.1C≤I c2 ≤6C; V c2 2~4V.

[0025] The present invention also provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the battery charging and discharging method.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) The battery charging and discharging method provided by the present invention monitors the working conditions and working environment of the sodium ion battery, and proposes different charging and discharging strategies for different charging and discharging conditions and the ambient temperature of the battery. Due to the unique characteristic of sodium ion batteries that can be discharged to 0V, they are applied in low-temperature environments to make the chemical reaction inside the battery closer to a balanced state, which helps to eliminate polarization, thereby improving the low-temperature charging and discharging cycle performance of the sodium ion battery. The method is low-cost and easy to implement.

[0028] (2) The battery charging and discharging method provided by the present invention further adopts a "constant current charging" mode to avoid the long constant voltage process caused by low temperature. Under the premise of not affecting the charging efficiency, the low temperature cycle performance of the sodium ion battery is further improved by combining the "constant current discharge to a cut-off voltage of 0V" scheme.

[0029] (3) The battery charging and discharging method provided by the present invention collects the working environment temperature of the battery and executes relevant charging and discharging strategies according to the ambient temperature. When in a low temperature environment, it charges with a smaller constant current and then discharges with a constant current to 0V, thereby improving the energy efficiency of the battery.

[0030] (4) The battery charging and discharging method provided by the present invention optimizes the charging upper limit voltage (i.e., the charging cut-off voltage V c1 ), the battery will not have sodium precipitation phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0032] Figure 1 A flow chart of a battery charging and discharging method provided by the present invention;

[0033] Figure 2 A comparison chart of the capacity retention rates of Example 1, Example 2 and Example 3 provided by the present invention;

[0034] Figure 3 A comparison chart of energy efficiencies of Embodiment 1, Embodiment 2, and Embodiment 3 provided by the present invention;

[0035] Figure 4 A comparison chart of the capacity retention rates of Comparative Example 1, Comparative Example 2 and Comparative Example 3 provided by the present invention;

[0036] Figure 5 A comparison chart of the energy efficiencies of Comparative Examples 1, 2 and 3 provided by the present invention;

[0037] Figure 6 A comparison chart of the capacity retention rates of Example 4 and Example 5 provided by the present invention;

[0038] Figure 7 A comparison chart of energy efficiency between Example 4 and Example 5 provided by the present invention;

[0039] Figure 8 A comparison chart of the capacity retention rates of Comparative Example 4 and Comparative Example 5 provided by the present invention;

[0040] Fig. 9 A comparison chart of energy efficiency between Comparative Example 4 and Comparative Example 5 provided by the present invention;

[0041] Fig.10 This is a picture of the negative electrode sheet after disassembly of Example 1 provided by the present invention;

[0042] Fig.11 This is a picture of the negative electrode sheet after disassembly of Example 5 provided by the present invention;

[0043] Fig.12This is a picture of the negative electrode sheet after disassembly of Comparative Example 1 provided by the present invention;

[0044] Fig.13 This is a picture of the negative electrode sheet after disassembly of comparative example 5 provided by the present invention. DETAILED DESCRIPTION

[0045] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0046] If there is no special explanation, in the present invention, "the first aspect", "the second aspect", "the third aspect", "the fourth aspect", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "the first", "the second", "the third", "the fourth", etc. only serve the purpose of non-exhaustive enumeration and description, and it should be understood that they do not constitute a closed limitation on quantity.

[0047] If there is no special explanation, the "include" and "comprising" mentioned in the present invention represent open-ended or closed-ended expressions. For example, the "include" and "comprising" may represent that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0048] If there is no special explanation, in the present invention, "one or more" or "at least one" refers to any one, any two or more of the listed items. Among them, "several" refers to any two or more of the listed items.

[0049] In a first aspect, the present invention provides a battery charge and discharge management method, which manages the charge and discharge of the sodium ion battery by monitoring the charge and discharge operating condition information of the sodium ion battery and the battery working environment temperature, thereby improving the charge and discharge performance of the sodium ion battery.

[0050] like Figure 1The figure shows a flow chart of the battery charging and discharging method provided by the present invention. The battery charging and discharging method comprises: obtaining the charging and discharging condition information and the ambient temperature of the sodium ion battery; judging the charging and discharging condition information and the ambient temperature of the sodium ion battery; when the sodium ion battery is in the discharging condition and the ambient temperature is lower than the preset temperature threshold, performing constant current discharge and discharging to the cut-off voltage V d1 , the V d1 When the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, a constant current discharge is performed and the battery is discharged to a cut-off voltage V d2 When the sodium ion battery is in a charging condition and the temperature environment is lower than the preset temperature threshold, constant current charging is performed and charged to a cut-off voltage of V c1 When the sodium ion battery is in a charging condition and the ambient temperature is greater than or equal to a preset temperature threshold, constant current and constant voltage charging is performed.

[0051] It can be understood that the above-mentioned sodium ion battery includes batteries, battery cells, and battery cells.

[0052] The battery charging and discharging method provided by the present invention monitors the working condition of the sodium ion battery and the ambient temperature in which it is located, and proposes different charging and discharging strategies for different charging and discharging working conditions and the ambient temperature in which the battery is operating. Due to the special characteristic of the sodium ion battery that it can be discharged to 0V, it is applied in a low-temperature environment, so that the chemical reaction inside the battery is closer to a balanced state, which helps to eliminate polarization, thereby improving the low-temperature charging and discharging cycle performance of the sodium ion battery, and will not cause irreversible effects on its internal structure.

[0053] The battery charging and discharging method provided by the present invention is low-cost and easy to implement. It does not require additional equipment investment or large-scale research and development of materials, and can achieve low-cost and high-efficiency battery low-temperature performance improvement, which is expected to solve the problem of limited low-temperature performance in the prior art and provide possibilities for the application of sodium ion batteries in a wider range of fields.

[0054] At the same time, the present invention adopts the "constant current charging" mode, which can avoid the situation where long-term constant voltage charging in a low temperature environment reduces the charging efficiency, that is, the low temperature charging efficiency is not significantly affected.

[0055] In addition, the battery charging and discharging method provided by the present invention can not only obtain a high capacity retention rate, but also has stable energy efficiency, high discharge capacity and high discharge energy value.

[0056] In some specific implementations, the preset temperature threshold is 25°C.

[0057] In some specific embodiments, when the sodium ion battery is in a discharge condition and the ambient temperature is lower than 25°C and greater than or equal to -30°C, a constant current discharge is performed and the battery is discharged to a cut-off voltage V d1 , the V d1 When the sodium ion battery is in a discharge condition and the ambient temperature is 25-60°C, a constant current discharge is performed and the discharge is discharged to a cut-off voltage V d2 When the sodium ion battery is in a charging condition and the temperature environment is lower than 25°C and greater than or equal to -30°C, constant current charging is performed and charged to a cut-off voltage of V c1 When the sodium ion battery is in a charging condition and the ambient temperature is 25-60°C, constant current and constant voltage charging is performed.

[0058] In some specific embodiments, in order to further improve the low-temperature charge and discharge cycle performance of the sodium ion battery, when the sodium ion battery is in a discharge condition and the ambient temperature is lower than a preset temperature threshold, the discharge current I of the constant current discharge is d1 Satisfy 0.1C≤I d1 ≤3C, where I d1 Including but not limited to any one of the point values ​​of 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.8C, 1C, 1.5C, 2C, 2.5C, 3C or the range value between any two of them.

[0059] In some specific embodiments, in order to further improve the comprehensive performance of the sodium ion battery such as cycle, energy efficiency, and capacity, when the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, the constant current discharge is performed to a discharge cut-off voltage V d2 It is 0-4V, including but not limited to any point value of 0V, 0.01V, 0.03V, 0.05V, 0.1V, 0.2V, 0.3V, 0.5V, 0.8V, 1V, 1.3V, 1.5V, 2V, 2.5V, 3V, 3.1V, 3.3V, 3.5V, 3.7V, 3.8V, 4V or the range value between any two of them.

[0060] In some specific embodiments, in order to further improve the comprehensive performance of the sodium ion battery such as cycle, energy efficiency, and capacity, when the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, the discharge current I of the constant current discharge is d2 Satisfy 0.1C≤I d2≤6C; including but not limited to any one of 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.8C, 1C, 1.5C, 2C, 2.5C, 3C, 3.5C, 4C, 4.5C, 5C, 5.5C, 6C or the range between any two of them.

[0061] In some specific embodiments, in order to further improve the low-temperature charge and discharge cycle performance of the sodium ion battery, when the sodium ion battery is in a charging condition and the temperature environment is lower than a preset temperature threshold, the constant current charging is performed until the cut-off voltage V c1 It is 2-4V, including but not limited to any point value of 2V, 2.3V, 2.5V, 2.8V, 3V, 3.1V, 3.2V, 3.3V, 3.5V, 3.6V, 3.7V, 3.8V, 4V or a range between any two of them.

[0062] In some specific implementations, in order to avoid the sodium precipitation phenomenon, the V c1 It is 2 to 3.7V, including but not limited to any point value of 2V, 2.3V, 2.5V, 2.8V, 2.9V, 3V, 3.1V, 3.2V, 3.3V, 3.5V, 3.6V, and 3.7V, or a range between any two of them.

[0063] In some specific embodiments, in order to further improve the low-temperature charge and discharge cycle performance of the sodium ion battery, when the sodium ion battery is in a charging condition and the temperature environment is lower than a preset temperature threshold, the charging current I of the constant current charging is c1 Satisfy 0.01C≤I c1 ≤1C; including but not limited to any point value of 0.01C, 0.03C, 0.05C, 0.08C, 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.6C, 0.8C, 1C or the range value between any two of them.

[0064] In some specific embodiments, in order to further improve the energy efficiency of the sodium ion battery, the I c1 Satisfy 0.01C≤I c1 <0.5C, including but not limited to any one of 0.01C, 0.03C, 0.05C, 0.08C, 0.1C, 0.15C, 0.2C, 0.25C, 0.3C, 0.4C, 0.49C or the range between any two of them.

[0065] In some specific embodiments, in order to improve the battery performance such as capacity retention rate, energy efficiency, charge and discharge capacity and charge and discharge energy of the sodium ion battery, the constant current constant voltage charging includes: first charging the sodium ion battery with a charging current of Ic2 Perform constant current charging until the charging cut-off voltage is V c2 , then with the V c2 Constant voltage charging until the current drops to 0.05I c2 Stop charging when

[0066] In some specific embodiments, in order to further improve the performance of the sodium ion battery such as capacity retention rate, energy efficiency, charge and discharge capacity and charge and discharge energy, the I c2 Satisfy 0.1C≤I c2 ≤6C; including but not limited to any one of 0.1C, 0.2C, 0.3C, 0.4C, 0.5C, 0.8C, 1C, 1.5C, 2C, 2.5C, 3C, 3.5C, 4C, 4.5C, 5C, 5.5C, 6C or the range between any two of them.

[0067] In some specific embodiments, in order to further improve the capacity retention rate, energy efficiency, charge and discharge capacity, and charge and discharge energy of the sodium ion battery, the V c2 It is 2-4V, including but not limited to any point value of 2V, 2.3V, 2.5V, 2.8V, 3V, 3.1V, 3.2V, 3.3V, 3.5V, 3.6V, 3.7V, 3.8V, 3.9V, 4V or a range between any two of them.

[0068] The present invention proposes charging and discharging strategies for low-temperature discharge, low-temperature charge, normal temperature or high temperature charge, and normal temperature or high temperature discharge, which can improve the capacity retention rate, energy conversion efficiency, discharge capacity and discharge energy value of the battery under various operating conditions.

[0069] In a second aspect, the present invention provides an electronic device, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the above-mentioned battery charging and discharging method.

[0070] The embodiments of the present invention will be described in detail below in conjunction with the examples, but it will be appreciated by those skilled in the art that the following examples are only used to illustrate the present invention and should not be considered as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to normal conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0071] The battery cells used in the following embodiments and comparative examples are from the same batch.

[0072] Example 1

[0073] The battery (cell) charging and discharging method provided in this embodiment is as follows:

[0074] Obtain the charging and discharging condition information of the sodium ion battery and the ambient temperature, wherein the ambient temperature is -20°C.

[0075] Determine the charging and discharging conditions of the sodium-ion battery and the ambient temperature.

[0076] The battery cell is placed in a preset low temperature environment of -20℃ to make the battery cell reach thermal equilibrium, and a 10-week low temperature cycle is performed using the "stand-by-constant current charge-stand-by-constant current discharge" system. Specifically, the battery cell is first placed at -20℃ for 6 hours to make the battery cell reach thermal equilibrium. Then the preset charging current I c1 =0.1C, charge the battery with constant current until the charging cut-off voltage V c1 3.5V. Then place the battery at -20℃ for 30min and discharge it with a discharge current I d1 = 0.5C to discharge the battery cell at a constant current until the discharge cut-off voltage V d1 The above-mentioned "stand-by-constant current charge-stand-by-constant current discharge" mode is adopted for 10 cycles of continuous charge and discharge.

[0077] Example 2

[0078] The battery charging and discharging method provided in this embodiment is basically the same as that in embodiment 1, except that the constant current charging is performed until the charging cut-off voltage V c1 is 3.6V.

[0079] Example 3

[0080] The battery charging and discharging method provided in this embodiment is basically the same as that in embodiment 1, except that the constant current charging is performed until the charging cut-off voltage V c1 is 3.7V.

[0081] Comparative Example 1

[0082] The battery charging and discharging method provided in this comparative example is basically the same as that in Example 1, except that the battery is discharged at a constant current until the discharge cut-off voltage V d1 is 2V.

[0083] Comparative Example 2

[0084] The battery charging and discharging method provided in this comparative example is basically the same as that in comparative example 1, except that the constant current charging is performed until the charging cut-off voltage V c1 is 3.6V.

[0085] Comparative Example 3

[0086] The battery charging and discharging method provided in this comparative example is basically the same as that in comparative example 1, except that the constant current charging is performed until the charging cut-off voltage V c1 is 3.7V.

[0087] The capacity retention rate and energy efficiency of the batteries of Examples 1 to 3 and Comparative Examples 1 to 3 during the cycle were calculated respectively. Wherein, capacity retention rate = battery cycle discharge capacity / battery initial discharge capacity × 100%, energy efficiency = battery cycle discharge energy / battery cycle charge energy × 100%. The capacity retention rate and energy efficiency results of Example 1 and Comparative Example 1 are shown in Table 1. The capacity retention rate comparison curve of Example 1, Example 2 and Example 3 can be found in Figure 2 The energy efficiency comparison curves of Example 1, Example 2 and Example 3 are shown in Figure 3 The capacity retention rate comparison curves of Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown in Figure 4 The energy efficiency comparison curves of Comparative Example 1, Comparative Example 2 and Comparative Example 3 are shown in Figure 5 .

[0088] Table 1 Capacity retention and energy efficiency of Example 1 and Comparative Example 1

[0089]

[0090]

[0091] From Table 1 and Figure 2 to Figure 5 It can be seen that the charging and discharging strategy of Example 1 can enable the battery cell to exhibit a higher and more stable capacity retention rate and more stable energy efficiency in a low temperature environment. Compared with "constant current discharge to 2V", the method provided by the present invention (constant current discharge to 0V) has obvious advantages in improving the low temperature cycle performance of sodium ion batteries.

[0092] At the same time, by comparing Figure 2 and Figure 3 It can be seen that in Example 1, the constant current charging to a cut-off voltage of 3.5V has the best capacity retention rate.

[0093] The test found that placing the battery cells in other preset low temperature environments (-10℃, 20℃) also has the same effect as above (compared with "constant current discharge to 2V", the "constant current discharge to 0V" method shows a higher and more stable capacity retention rate, as well as more stable energy efficiency).

[0094] Example 4

[0095] The battery charging and discharging method provided in this embodiment is basically the same as that in embodiment 1, except that the constant current charging is performed until the charging cut-off voltage V c1 The charging current I is 3.1V and the constant current charging c1 =0.5C.

[0096] Example 5

[0097] The battery charging and discharging method provided in this embodiment is basically the same as that in embodiment 1, except that the constant current charging is performed until the charging cut-off voltage V c1 The charging current I is 3.2V and the constant current charging c1 =0.5C.

[0098] Comparative Example 4

[0099] The battery charging and discharging method provided in this comparative example is basically the same as that in comparative example 1, except that the constant current charging is performed until the charging cut-off voltage V c1 The charging current I is 3.1V and the constant current charging c1 =0.5C.

[0100] Comparative Example 5

[0101] The battery charging and discharging method provided in this comparative example is basically the same as that in comparative example 1, except that the constant current charging is performed until the charging cut-off voltage V c1 The charging current I is 3.2V and the constant current charging c1 =0.5C.

[0102] The capacity retention rate and energy efficiency of the batteries of Examples 4 to 5 and Comparative Examples 4 to 5 during the cycle were calculated respectively. Wherein, capacity retention rate = battery cycle discharge capacity / battery initial discharge capacity × 100%, energy efficiency = battery cycle discharge energy / battery cycle charge energy × 100%. The capacity retention rate and energy efficiency results of Example 4 and Comparative Example 4 are shown in Table 2. The capacity retention rate comparison curve of Example 4 and Example 5 can be found in Figure 6 The energy efficiency comparison curve of Example 4 and Example 5 is shown in Figure 7 The capacity retention rate comparison curve of Comparative Example 4 and Comparative Example 5 is shown in Figure 8 The energy efficiency comparison curves of Comparative Example 4 and Comparative Example 5 are shown in Fig. 9 .

[0103] Table 2 Capacity retention and energy efficiency of Example 4 and Comparative Example 4

[0104]

[0105] Compared with Example 1, Example 4 and Example 5 use a larger current for charging, which improves the charging efficiency. By comparing Example 1, Example 4 and Example 5, it can be found that even if the low-temperature charging rate is increased and the cycle is performed according to the strategy of "constant current discharge to 0V", the battery cell can still exert good electrochemical cycle performance in a low-temperature environment.

[0106] Moreover, compared with Comparative Examples 4 and 5, Examples 4 and 5 still have obvious advantages in improving the low-temperature cycle performance of the battery.

[0107] In addition, by comparing Examples 1 to 3 and Examples 4 to 5, it can be seen that the energy efficiency in Examples 1 to 3 is better, which indicates that the energy efficiency of the battery can be further improved by using a small current for constant current charging.

[0108] Furthermore, the discharge capacity and discharge energy results of each embodiment and each comparative example are shown in Table 3.

[0109] Specifically, in each embodiment, “actual discharge capacity in the last week” and “actual discharge energy in the last week” are respectively the discharge capacity of the battery cell from V c1 The total discharge capacity and total discharge energy during the constant current discharge to 0V; "2V discharge capacity" and "2V discharge energy" are the discharge capacity and energy of the battery cell from V c1 At the beginning, the partial discharge capacity and partial discharge energy during the constant current discharge to 2V. For example, in Example 1, c1 = 0.1C charging current constant current charging to cut-off voltage V c1 =3.5V, then I d1 = 0.5C discharge current constant current discharge to cut-off voltage V d1 The actual discharge capacity at the 10th cycle, i.e. the last cycle, was 6.5909Ah and the actual discharge energy was 15.0208Wh. The capacity value when the battery was discharged to 2V in the last cycle was 5.0814Ah and the energy value was 12.7769Wh.

[0110] In each comparison, “actual discharge capacity in the last week” and “2V discharge capacity” are the discharge capacity of the battery from V c1 The total discharge capacity during the constant current discharge to 2V. The “actual discharge energy in the last week” and “2V discharge energy” are both the discharge energy of the battery from V c1 At the beginning, the total discharge energy during the constant current discharge to 2V. c1 = 0.1C charging current constant current charging to cut-off voltage V c1 =3.5V, then I d1 = 0.5C discharge current constant current discharge to cut-off voltage V d1 The actual discharge capacity at the 10th cycle, i.e. the last cycle, was 4.1090 Ah and the actual discharge energy was 10.0710 Wh.

[0111] Table 3 Discharge capacity and discharge energy results of each embodiment and each comparative example

[0112]

[0113]

[0114] It can be seen from Table 3 that the discharge capacity value and discharge energy value of each group of embodiments are significantly greater than the discharge capacity value and discharge energy value of the corresponding proportion. This shows that the battery charge and discharge management method provided by the present invention can improve the capacity of the sodium ion battery while improving the cycle performance.

[0115] In addition, by disassembling and observing the battery cells after the cycle, it was found that when the upper limit charging voltage was set to 3.5V, 3.6V, and 3.7V in Example 1, Example 2, and Example 3, respectively, the battery would not experience sodium precipitation.

[0116] The negative electrode sheet after disassembly of Example 1 is shown in the figure Fig.10 As shown, the negative electrode sheet after disassembly of Example 5 is shown in Fig.11 As shown, the negative electrode sheet after disassembly of comparative example 1 is shown in Fig.12 As shown, the negative electrode sheet after disassembly of comparative example 5 is shown in Fig.13 As shown. Figure 10 to Figure 13 It can be seen that no sodium precipitation occurs in any of the batteries.

[0117] At the same time, the battery cells of each embodiment and each comparative example after cycling were disassembled to observe whether there was irreversible damage to the internal structure of each battery cell. The results showed that each embodiment and each comparative example had no impact on the internal structure of the battery cell.

[0118] Although the present invention has been illustrated and described with specific embodiments, it should be appreciated that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents without departing from the spirit and scope of the present invention. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A battery charging and discharging method, characterized in that: The steps include: Obtain the charging and discharging condition information and ambient temperature of the sodium ion battery; Determining the charging and discharging condition information of the sodium ion battery and the ambient temperature; When the sodium ion battery is in a discharge condition and the ambient temperature is lower than a preset temperature threshold, a constant current discharge is performed and the battery is discharged to a cut-off voltage V d1 When the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, a constant current discharge is performed and the battery is discharged to a cut-off voltage V d2 ; When the sodium ion battery is in a charging condition and the temperature environment is lower than the preset temperature threshold, constant current charging is performed and charged to a cut-off voltage of V c1 ; When the sodium ion battery is in a charging condition and the ambient temperature is greater than or equal to a preset temperature threshold, constant current and constant voltage charging is performed; The V d1 is 0V.

2. The battery charging and discharging method according to claim 1, characterized in that: The preset temperature threshold is 25°C.

3. The battery charging and discharging method according to claim 1, characterized in that: When the sodium ion battery is in a discharging condition and the ambient temperature is lower than a preset temperature threshold, the discharge current I d1 Satisfy 0.1C≤I d1 ≤3C.

4. The battery charging and discharging method according to claim 1, characterized in that: When the sodium ion battery is in a discharge condition and the ambient temperature is greater than or equal to a preset temperature threshold, the constant current discharge is performed to a discharge cut-off voltage V d2 0~4V.

5. The battery charging and discharging method according to claim 4, characterized in that: When the sodium ion battery is in a discharging condition and the ambient temperature is greater than or equal to a preset temperature threshold, the discharge current I of the constant current discharge is d2 Satisfy 0.1C≤I d2 ≤6C.

6. The battery charging and discharging method according to claim 1, characterized in that: When the sodium ion battery is in a charging condition and the temperature environment is lower than a preset temperature threshold, the constant current charging is performed until the cut-off voltage V c1 2~4V; Preferably, the V c1 It is 2~3.7V.

7. The battery charging and discharging method according to claim 6, characterized in that: When the sodium ion battery is in a charging condition and the temperature environment is lower than a preset temperature threshold, the charging current I c1 Satisfy 0.01C≤I c1 ≤1C.

8. The battery charging and discharging method according to claim 1, characterized in that: The constant current constant voltage charging comprises: first charging the sodium ion battery with a charging current of I c2 Perform constant current charging until the charging cut-off voltage is V c2 , then with the V c2 Constant voltage charging until the current drops to 0.05I c2 Stop charging when 9. The battery charging and discharging method according to claim 8, characterized in that: I c2 Satisfy 0.1C≤I c2 ≤6C; V c2 2~4V.

10. An electronic device, characterized in that: The invention comprises a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement the battery charging and discharging method according to any one of claims 1 to 9.

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