Novel sodium ion battery and formation method thereof

Abstract

The invention discloses a novel sodium ion battery and a formation method thereof, and belongs to the technical field of sodium ion batteries. A formation method of a novel sodium-ion battery comprises the following steps: S1, placing the sodium-ion battery in a constant-temperature environment, and charging the sodium-ion battery to 0.5 V through a first constant current to obtain a first formation stage battery; s2, charging the battery in the first formation stage to 3.8 V through a second constant current, and then converting into constant-voltage charging until the charging current is reduced to 0.02 C, so as to obtain a battery in a second formation stage; s3, standing the battery in the second formation stage to obtain a battery after standing; s4, the battery after standing is discharged to 1.0 V through a third current in a constant-current mode and then charged to 3.8 V through a fourth current in a constant-current mode, and a third formation stage battery is obtained; and S5, carrying out charge-discharge circulation on the battery in the third formation stage until the formation is finished. The formation method of the sodium-ion battery can improve the electrochemical performance of the sodium-ion battery.

Description

Technical Field

[0001] The invention belongs to the technical field of sodium ion batteries, and in particular relates to a novel sodium ion battery and a formation method thereof. Background Art

[0002] Sodium-ion batteries have become a highly promising next-generation energy storage battery system due to their advantages such as abundant sodium resources and low cost. Formation, as a core process in the production of sodium-ion batteries, is of self-evident importance. This process aims to form a stable and dense solid electrolyte interface film (SE I film) on the surface of the electrode through a series of complex electrochemical reactions during the first charge and discharge of the battery. This SE I film can not only effectively isolate the direct contact between the electrolyte and the electrode, prevent electrolyte decomposition and internal short circuit of the battery, but also promote the smooth migration of ions to ensure the normal operation of the battery. At the same time, the formation process can also fully activate the active substances in the battery, further improve the electrochemical performance of the battery, thereby stabilizing and optimizing the overall performance of the battery.

[0003] The existing sodium-ion battery formation method has problems such as unstable SE I film quality, low formation efficiency, and poor battery consistency, which limits the large-scale application and performance improvement of sodium-ion batteries. Therefore, how to optimize the formation process and improve the performance and production efficiency of sodium-ion batteries is a technical problem that needs to be solved urgently. Summary of the invention

[0004] In order to solve the problems of unstable SE I film quality, low formation efficiency, poor battery consistency, etc. in the existing sodium ion battery formation method, which limits the large-scale application and performance improvement of sodium ion batteries, the object of the present invention is to provide a novel sodium ion battery and its formation method.

[0005] The purpose of the present invention can be achieved through the following technical solutions:

[0006] In a first aspect, the present invention provides a novel sodium ion battery formation method, comprising the following steps:

[0007] S1: placing the sodium ion battery in a constant temperature environment, charging it to 0.5V using a first constant current, and obtaining a first formation stage battery;

[0008] This step belongs to the pre-activation stage. The purpose of the pre-activation stage is to initially activate the electrode material so that sodium ions begin to embed and extract in small amounts between the positive and negative electrodes, laying the foundation for the subsequent formation of a good SE I film. The formation of the SE I film is important for the long-term stability and safety of battery performance. It can effectively prevent solvent molecules from being co-embedded in the electrode material, reduce the occurrence of side reactions, thereby protecting the electrode structure and extending the battery life.

[0009] S2: The first formation stage battery is charged to 3.8V by the second current constant current, and then switched to constant voltage charging until the charging current drops to 0.02C, thereby obtaining a second formation stage battery;

[0010] This step belongs to the SE I film formation stage. During this process, the SE I film will gradually form on the electrode surface. By controlling the appropriate current density and voltage range, the formation of the SE I film can be made more uniform and dense, thereby improving the cycle stability and safety of the battery.

[0011] S3: allowing the second formation stage battery to stand still to obtain a battery after standing still;

[0012] This step belongs to the static equilibrium stage. During the static process, the ion concentration and potential distribution inside the battery will gradually tend to equilibrium, which will help eliminate stress and polarization inside the battery and further improve the consistency of the battery.

[0013] S4: discharging the stationary battery to 1.0V by a third constant current, and then charging it to 3.8V by a fourth constant current, to obtain a third formation stage battery;

[0014] This step belongs to the capacity activation stage. In this stage, the active sites of the electrode material are further activated through charging and discharging at a certain rate, so that the battery reaches its rated capacity. At the same time, the SE I membrane is further optimized and stabilized.

[0015] S5: The battery in the third formation stage is subjected to a charge and discharge cycle, and the formation is now completed.

[0016] This step belongs to the cycle optimization stage. Through multiple cycles, the reaction inside the battery can be more complete and the structure of the electrode material can be more stable, thereby improving the overall performance and consistency of the battery.

[0017] Further, in step S1, the temperature of the constant temperature environment is 25±2°C, and the first current is 0.03C-0.1C.

[0018] Further, in step S2, the second current is 0.05C-0.1C.

[0019] Furthermore, in step S3, the standing time is 2.5-3.5 hours.

[0020] Further, in step S4, the third current and the fourth current are both 0.2C.

[0021] Furthermore, in step S5, the number of charge and discharge cycles is 3-6 times.

[0022] Further, in step S5, each charge-discharge cycle includes the following steps performed in sequence: the charge current is 0.5C, and the charge cut-off voltage is 3.8V; the discharge current is 0.5C, and the discharge cut-off voltage is 1.0V.

[0023] In a second aspect, the present invention provides a novel sodium-ion battery, which is made by the formation method of a novel sodium-ion battery described in any one of the above.

[0024] Advantages of the present invention:

[0025] 1. By controlling the current and voltage parameters in stages, the present invention optimizes the formation process of the solid electrolyte interface film, ensuring that its structure is more uniform and dense. This strategy significantly improves the cycle stability performance of the battery and enhances the overall safety of the battery during use.

[0026] 2. Through reasonable current setting and stage planning, the present invention effectively reduces the unnecessary charging time, significantly improves the formation efficiency, and further reduces the production cost.

[0027] 3. By introducing a static equilibrium stage and a multi-cycle optimization stage, these two key steps ensure the precise alignment and high consistency of the internal state of the battery. This approach directly enhances the collaborative working efficiency among the units in the battery pack, significantly optimizes the overall performance of the battery pack, and greatly improves its operating stability and reliability. Specific embodiments

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0029] Embodiment 1

[0030] The formation method of a novel sodium-ion battery in this embodiment includes the following steps:

[0031] S1: Place the assembled sodium-ion battery in a constant temperature environment and charge it at a constant current of 0.05C to 1.5V at 25°C to obtain a battery in the first formation stage;

[0032] S2: Charge the battery in the first formation stage at a constant current of 0.1C to 3.8V, and then switch to constant voltage charging until the charging current drops to 0.02C to obtain a battery in the second formation stage;

[0033] S3: Let the battery in the second formation stage stand for 2.5 hours to obtain a standing battery;

[0034] S4: Discharge the battery after standing at a rate of 0.2C until 1.0V, then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the third formation stage;

[0035] S5: Perform 4 charge-discharge cycles on the battery in the third formation stage. Each charge-discharge cycle includes the following steps performed in sequence: the charge current is 0.5C and the charge cut-off voltage is 3.8V; the discharge current is 0.5C and the discharge cut-off voltage is 1.0V. After the cycles, the formation is completed.

[0036] Example 2

[0037] A formation method for a new type of sodium-ion battery in this example includes the following steps:

[0038] S1: Place the assembled sodium-ion battery in a constant-temperature environment and charge it at a constant current of 0.03C at 25°C to 1.5V to obtain the battery in the first formation stage;

[0039] S2: Charge the battery in the first formation stage at a constant current of 0.1C to 3.8V, then switch to constant-voltage charging until the charge current drops to 0.02C to obtain the battery in the second formation stage;

[0040] S3: Let the battery in the second formation stage stand for 2.5 hours to obtain the battery after standing;

[0041] S4: Discharge the battery after standing at a rate of 0.2C until 1.0V, then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the third formation stage;

[0042] S5: Perform 4 charge-discharge cycles on the battery in the third formation stage. Each charge-discharge cycle includes the following steps performed in sequence: the charge current is 0.5C and the charge cut-off voltage is 3.8V; the discharge current is 0.5C and the discharge cut-off voltage is 1.0V. After the cycles, the formation is completed.

[0043] Example 3

[0044] A formation method for a new type of sodium-ion battery in this example includes the following steps:

[0045] S1: Place the assembled sodium-ion battery in a constant-temperature environment and charge it at a constant current of 0.05C at 25°C to 1.5V to obtain the battery in the first formation stage;

[0046] S2: Charge the battery in the first formation stage at a constant current of 0.05C to 3.8V, then switch to constant-voltage charging until the charge current drops to 0.02C to obtain the battery in the second formation stage;

[0047] S3: Let the battery in the second formation stage stand for 2.5 hours to obtain the battery after standing.

[0048] S4: Discharge the battery after standing at 0.2C to 1.0V, and then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the third formation stage.

[0049] S5: Perform 4 charge-discharge cycles on the battery in the third formation stage. Each charge-discharge cycle includes the following steps carried out in sequence: the charge current is 0.5C, and the charge cut-off voltage is 3.8V; the discharge current is 0.5C, and the discharge cut-off voltage is 1.0V. After the cycles, the formation ends.

[0050] Example 4

[0051] A formation method for a new type of sodium-ion battery in this example includes the following steps:

[0052] S1: Place the assembled sodium-ion battery in a constant-temperature environment and charge it at a constant current of 0.05C to 1.5V at 25°C to obtain the battery in the first formation stage.

[0053] S2: Charge the battery in the first formation stage at a constant current of 0.1C to 3.8V, and then switch to constant-voltage charging until the charge current drops to 0.02C to obtain the battery in the second formation stage.

[0054] S3: Let the battery in the second formation stage stand for 3.5 hours to obtain the battery after standing.

[0055] S4: Discharge the battery after standing at 0.2C to 1.0V, and then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the third formation stage.

[0056] S5: Perform 4 charge-discharge cycles on the battery in the third formation stage. Each charge-discharge cycle includes the following steps carried out in sequence: the charge current is 0.5C, and the charge cut-off voltage is 3.8V; the discharge current is 0.5C, and the discharge cut-off voltage is 1.0V. After the cycles, the formation ends.

[0057] Example 5

[0058] A formation method for a new type of sodium-ion battery in this example includes the following steps:

[0059] S1: Place the assembled sodium-ion battery in a constant-temperature environment and charge it at a constant current of 0.05C to 1.5V at 25°C to obtain the battery in the first formation stage.

[0060] S2: Charge the battery in the first formation stage at a constant current of 0.1C to 3.8V, and then switch to constant-voltage charging until the charge current drops to 0.02C to obtain the battery in the second formation stage.

[0061] S3: Let the battery in the second formation stage stand still for 2.5 hours to obtain the battery after standing still.

[0062] S4: Discharge the battery after standing still at 0.2C to 1.0V, and then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the third formation stage.

[0063] S5: Perform 6 charge-discharge cycles on the battery in the third formation stage. Each charge-discharge cycle includes the following steps carried out in sequence: the charging current is 0.5C, and the charging cut-off voltage is 3.8V; the discharging current is 0.5C, and the discharging cut-off voltage is 1.0V. After the cycles, the formation ends.

[0064] Comparative Example 1

[0065] The formation method of a new type of sodium-ion battery in this comparative example includes the following steps:

[0066] S1: Charge the assembled sodium-ion battery at a constant current of 0.1C to 3.8V, and then switch to constant voltage charging until the charging current drops to 0.02C to obtain the battery in the first formation stage.

[0067] S2: Let the battery in the first formation stage stand still for 2.5 hours to obtain the battery after standing still.

[0068] S3: Discharge the battery after standing still at 0.2C to 1.0V, and then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the second formation stage.

[0069] S4: Perform 4 charge-discharge cycles on the battery in the second formation stage. Each charge-discharge cycle includes the following steps carried out in sequence: the charging current is 0.5C, and the charging cut-off voltage is 3.8V; the discharging current is 0.5C, and the discharging cut-off voltage is 1.0V. After the cycles, the formation ends.

[0070] Comparative Example 2

[0071] The formation method of a new type of sodium-ion battery in this comparative example includes the following steps:

[0072] S1: Place the assembled sodium-ion battery in a constant temperature environment and charge it at a constant current of 0.05C to 1.5V at 25°C to obtain the battery in the first formation stage.

[0073] S2: Charge the battery in the first formation stage at a constant current of 0.1C to 3.8V, and then switch to constant voltage charging until the charging current drops to 0.02C to obtain the battery in the second formation stage.

[0074] S3: Discharge the battery in the second formation stage at 0.2C to 1.0V, and then charge it at a constant current of 0.2C to 3.8V to obtain the battery in the third formation stage.

[0075] S4: The third formation stage battery is subjected to 4 charge and discharge cycles, each charge and discharge cycle comprising the following steps in sequence: a charge current of 0.5C and a charge cut-off voltage of 3.8V; a discharge current of 0.5C and a discharge cut-off voltage of 1.0V. After the cycle, the formation is completed.

[0076] Comparative Example 3

[0077] A novel sodium ion battery formation method of this comparative example comprises the following steps:

[0078] S1: placing the assembled sodium ion battery in a constant temperature environment, charging it to 1.5V at a constant current of 0.05C at 25°C, and obtaining a first formation stage battery;

[0079] S2: The first formation stage battery is charged at 0.1C constant current to 3.8V, and then switched to constant voltage charging until the charging current drops to 0.02C, thereby obtaining a second formation stage battery;

[0080] S3: leaving the second formation stage battery to stand for 2.5 hours to obtain a battery after standing;

[0081] S4: The rested battery is discharged to 1.0V at 0.2C, and then charged to 3.8V at a constant current of 0.2C. This completes the formation.

[0082] The sodium ion batteries obtained in Examples 1 to 5 and Comparative Examples 1 to 3 were subjected to performance tests. At 25°C, the battery was charged at a constant current of 0.2C to a voltage of 4.5V, and discharged at a constant current of 0.2C to a voltage of 2V. The discharge capacity of the sodium ion battery was tested and recorded as C0. The cyclic charging was repeated under the same conditions as above, and the capacity of the battery after the 300th and 500th cycles was measured and recorded as C1. The capacity retention rate of the sodium ion battery after 300 or 500 cycles at 25°C = C1 / C0*100%. The capacity of the sub-capacity can be obtained by testing the sub-capacity cabinet, and the test results are shown in Table 1:

[0083] Table 1

[0084]

[0085]

[0086] It can be seen from Table 1 that the fractional capacity and capacity retention rate of the sodium ion batteries prepared in Examples 1 to 5 are better than those in Comparative Examples 1 to 3.

[0087] In Comparative Example 1, the pre-activation stage in Step S1 was omitted, and its electrochemical performance was lower than that of Example 1. The role of the pre-activation stage is to gradually activate the active substances inside the battery through low-current charging (such as 0.05C) to form a stable initial state. After omitting the pre-activation stage, the battery directly enters the SEI film formation stage, which may cause the following problems: 1. Insufficient activation of active substances: The active substances (such as the positive and negative electrode materials) inside the battery fail to react sufficiently, resulting in a low initial capacity. 2. Uneven SEI film: Since the inside of the battery does not reach a stable state, the formation of the SEI film may be uneven, affecting the cycle performance and safety of the battery. 3. Increased internal resistance: The internal resistance of the battery without pre-activation may be relatively high, resulting in a decrease in charge and discharge efficiency. The finally obtained sodium-ion battery has a low initial capacity, a shortened cycle life, and poor rate performance.

[0088] In Comparative Example 2, the static equilibrium stage in Step S3 was omitted, and its electrochemical performance was lower than that of Example 1. The role of the static equilibrium stage is to make the ion distribution and chemical reactions inside the battery reach an equilibrium state and further stabilize the SEI film. After omitting the static equilibrium stage, the following problems may occur: 1. Unstable SEI film: The SEI film is not allowed to stand sufficiently after formation, which may lead to an incomplete or uneven film structure, affecting the long-term stability of the battery. 2. Unreleased internal stress: The internal stress generated during the charge and discharge process of the battery is not released, which may cause microcracks or structural damage to the electrode material. 3. Uneven ion distribution: The lithium-ion distribution inside the battery is uneven, which may lead to local overcharging or over-discharging, affecting the battery performance. The finally obtained sodium-ion battery has a significantly reduced cycle life, an accelerated decline in battery capacity, and a reduced safety.

[0089] In Comparative Example 3, the cycle optimization stage in Step S5 was omitted, and its electrochemical performance was lower than that of Example 1. The role of the cycle optimization stage is to further stabilize the internal structure of the battery and activate more active substances through multiple charge and discharge cycles (such as 4 cycles of 0.5C). After omitting the cycle optimization stage, the following problems may occur: 1. Insufficient activation of active substances: The active substances inside the battery fail to be fully activated through cycling, resulting in an actual available capacity lower than the theoretical capacity. 2. Incomplete optimization of the SEI film: The SEI film is not optimized through cycling after initial formation, which may lead to a less dense film structure, affecting the cycle performance of the battery. 3. Sub-optimal electrochemical performance: The charge and discharge efficiency and rate performance of the battery fail to reach the optimal state through cycle optimization. The finally obtained sodium-ion battery has a low initial capacity, poor rate performance, and a shortened cycle life.

[0090] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprising", "including" or any other variation thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements not only includes those elements but also includes other elements not expressly listed, or elements inherent to such process, method, article or device.

[0091] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A formation method for a novel sodium-ion battery, characterized in that, It includes the following steps: S1: Place the sodium-ion battery in a constant-temperature environment and charge it at a constant current with a first current to 0.5V to obtain a battery in the first formation stage; S2: Charge the battery in the first formation stage at a constant current with a second current to 3.8V, and then switch to constant-voltage charging until the charging current drops to 0.02C to obtain a battery in the second formation stage; S3: Let the battery in the second formation stage stand to obtain a battery after standing; S4: Discharge the battery after standing at a constant current with a third current to 1.0V, and then charge it at a constant current with a fourth current to 3.8V to obtain a battery in the third formation stage; S5: Perform charge-discharge cycles on the battery in the third formation stage, and the formation is completed.

2. The formation method of a novel sodium-ion battery according to claim 1, characterized in that, In step S1, the temperature of the constant-temperature environment is 25±2°C.

3. The formation method of a novel sodium-ion battery according to claim 1, characterized in that In step S1, the first current is 0.03C - 0.1C.

4. The formation method of a novel sodium-ion battery according to claim 1, characterized in that, In step S2, the second current is 0.05C - 0.1C.

5. A formation method for a novel sodium-ion battery according to claim 1, characterized in that, In step S3, the standing time is 2.5 - 3.5 hours.

6. The formation method of a novel sodium-ion battery according to claim 1, characterized in that In step S4, the third current is 0.2C.

7. The formation method of a novel sodium-ion battery according to claim 1, characterized in that In step S4, the fourth current is 0.2C.

8. A formation method for a novel sodium ion battery according to claim 1, characterized in that, In step S5, the number of charge-discharge cycles is 3 - 6 times.

9. The formation method of a novel sodium-ion battery according to claim 1, characterized in that, In step S5, each charge-discharge cycle includes the following steps carried out in sequence: the charging current is 0.5C and the charging cut-off voltage is 3.8V; the discharging current is 0.5C and the discharging cut-off voltage is 1.0V.

10. A novel sodium-ion battery, characterized in that, It is made by the formation method of a novel sodium-ion battery according to any one of claims 1 - 9.

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