Charging method and use thereof

Abstract

Disclosed in the present disclosure are a charging method and the use thereof. The present disclosure relates to the technical field of lithium-ion battery charging. The disclosed charging method comprises the several following consecutive stages: the first stage: performing charging by using a high-rate current; the second stage: performing constant-current charging by using a first small-rate current to a set voltage; the third stage: performing constant-voltage charging by using the set voltage; performing a charging operation from the first stage to the third stage at least once; and the fourth stage: with the set voltage as a starting voltage, performing constant-current charging by using a second small-rate current until the voltage rises to a cut-off voltage of a battery, and then performing constant-voltage charging by using the cut-off voltage until the rate current is reduced to a charging cut-off current, wherein the value of the first small-rate current and the value of the second small-rate current are less than the value of the large-rate current, and the value of the set voltage is less than the value of the cut-off voltage. The charging method is rapid, and a battery has a long charging cycle life when charged using the charging method. The charging method is suitable for being applied to the charging of fast-charging batteries.

Description

Charging methods and their applications

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to application number 2023107022388, filed with the China Patent Office on June 14, 2023, entitled “Charging Method and Application Thereof,” the entire contents of which are incorporated by reference into this disclosure. Technical Field

[0003] The present disclosure relates to the field of lithium battery charging technology, and in particular to a charging method and application thereof. Background Art

[0004] With the development of lithium-ion battery technology, both in the consumer battery field and the power battery field, the market demand for fast charging is becoming increasingly strong, and the charging rate used is also getting higher and higher. As a result, a large number of lithium-ion secondary batteries with fast charging capabilities have emerged.

[0005] For fast-charging batteries, conventional charging methods include: (1) using a constant high-rate current to charge directly to the upper cutoff voltage to achieve fast charging; (2) using multiple current step charging methods to charge directly to the upper cutoff voltage to achieve fast charging. These existing charging methods can cause the internal polarization of lithium-ion batteries to increase rapidly, making it easy for the negative electrode to reach the lithium plating potential or lithium plating to occur during the cycle. At the same time, the charging temperature rises, making it difficult to dissipate internal heat, which accelerates electrolyte side reactions and consumption, and there is a risk of rapid cycle life degradation or even a sudden drop.

[0006] Therefore, it is necessary to develop a suitable charging method to reduce polarization growth and extend the life of lithium-ion batteries without affecting people's charging experience.

[0007] In view of this, the present disclosure is proposed.

[0008] Summary of the Invention

[0009] The purpose of the present disclosure is to provide a charging method and application thereof, aiming to improve at least one problem mentioned in the background technology.

[0010] The present disclosure is achieved as follows:

[0011] In a first aspect, the present disclosure provides a charging method comprising the following consecutive stages:

[0012] The first stage: charging with high rate current;

[0013] The second stage: using the first small rate current constant current charging to the set voltage;

[0014] The third stage: constant voltage charging using the set voltage;

[0015] Perform the charging operation from the first stage to the third stage at least once;

[0016] The fourth stage: starting with the set voltage, the second smallest rate current is used for constant current charging until the voltage rises to the cut-off voltage of the battery, and then constant voltage charging is performed at the cut-off voltage until the rate current decreases to the charging cut-off current;

[0017] The range of high rate current is: 1C≤high rate current≤the maximum rate charging current allowed by the battery;

[0018] The values ​​of the first low-rate current and the second low-rate current are smaller than the value of the high-rate current;

[0019] The set voltage value is smaller than the cut-off voltage value.

[0020] In an optional embodiment, the value of the first low-rate current is <1.0C;

[0021] In an optional embodiment, the value of the second small rate current is less than 1.0C;

[0022] In an optional embodiment, the charging operations from the first stage to the third stage are performed at least once until the state of charge of the battery is 30-98%, and then the fourth stage charging is performed.

[0023] In an optional embodiment, the difference between the set voltage and the cut-off voltage is 0.15 to 1.6V.

[0024] In an optional embodiment, in the third stage, the method of using the set voltage for constant voltage charging is:

[0025] (1) Current cut-off: constant voltage charging is performed until the rate current decreases to the charge cut-off current, and then the charging is cut off. Optionally, in this step, the charge cut-off current is 0.05C;

[0026] Alternatively, (2) the time limit is set to terminate after a certain period of constant voltage charging, which is ≤8 minutes.

[0027] In an optional embodiment, the charging cut-off current in the fourth stage is 0.02-0.05C.

[0028] In an optional embodiment, in the first stage, the high-rate current charging method is:

[0029] Use a constant high-rate current value for constant current charging;

[0030] Alternatively, step-by-step charging is performed at different high-rate current values ​​in different time periods;

[0031] Alternatively, charging is performed at a high rate current value that changes dynamically with charging time.

[0032] In an optional embodiment, the charging operation from the first stage to the third stage is performed once. During the first stage charging process, a high rate current is used to charge the battery to a state of charge of 50-80%.

[0033] In an optional embodiment, the charging operation from the first stage to the third stage is performed twice;

[0034] In the first stage of charging, a high rate current is used to charge the battery to a state of charge of 30-50%.

[0035] During the second first stage charging process, a high rate current is used to charge the battery to a state of charge of 50-80%.

[0036] In a second aspect, the present disclosure provides a charging method as described in any of the aforementioned embodiments for application in charging a fast-charging battery.

[0037] In an optional embodiment, the fast-charging battery is a ternary lithium-ion battery, a lithium cobalt oxide lithium-ion battery, a lithium iron phosphate lithium-ion battery, a lithium manganese oxide lithium-ion battery, or a manganese iron phosphate lithium-ion battery.

[0038] The present disclosure has the following beneficial effects:

[0039] The charging method provided by the present disclosure includes a constant voltage charging process after high-rate current charging. This process can eliminate or improve the polarization problem accumulated during the previous high-rate current charging process, increase the negative electrode potential, and avoid lithium deposition caused by excessive polarization, thereby preventing the impact on the fast-charge cycle life of the lithium-ion battery. Therefore, the charging method provided by the present disclosure has the characteristics of fast charging and less impact on the cycle life of the battery compared to the existing technology. In other words, charging with the charging method provided by the present disclosure can extend the cycle life of the battery. DETAILED DESCRIPTION

[0040] To make the purpose, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure are described clearly and completely below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer were followed. Reagents or instruments used where the manufacturer is not specified are conventional products that can be purchased commercially.

[0041] The features and performance of the present disclosure are further described in detail below with reference to the embodiments.

[0042] An embodiment of the present disclosure provides a charging method, including:

[0043] The first stage: charging with high rate current;

[0044] The second stage: using the first small rate current constant current charging to the set voltage;

[0045] The third stage: constant voltage charging is performed using the set voltage until the rate current decreases to the charging cut-off current;

[0046] Perform the charging operation from the first stage to the third stage at least once;

[0047] The fourth stage: starting with the set voltage, the second smallest rate current is used for constant current charging until the voltage rises to the cut-off voltage of the battery, and then constant voltage charging is performed at the cut-off voltage until the rate current decreases to the charging cut-off current;

[0048] The range of high rate current is: 1C≤high rate current≤the maximum rate charging current allowed by the battery;

[0049] The values ​​of the first low-rate current and the second low-rate current are smaller than the value of the high-rate current;

[0050] The set voltage value is smaller than the cut-off voltage value.

[0051] The charging method provided by the embodiment of the present disclosure adopts a high-rate current for charging in the first stage so that the battery can quickly reach a certain charge. However, charging with a high-rate current can easily cause the internal polarization of the lithium-ion battery to grow rapidly. In order to improve the polarization growth problem caused by the high-rate current, after charging with a high-rate current, a small-rate constant-current charging is used for transition in the second stage, followed by constant voltage charging in the third stage. The constant-voltage charging process is a process in which the current gradually decreases. During this process, the polarization problem caused by the high-rate current charging in the early stage can be well eliminated or improved. Finally, in the fourth stage, a small current is used to charge to the cut-off voltage, and constant voltage charging is performed at the cut-off voltage until the current drops to the charging cut-off current, and charging is completed.

[0052] Therefore, the charging method provided by the present disclosure, because a constant voltage charging process is provided after high-rate current charging, this process can eliminate or improve the polarization problem accumulated during the previous high-rate current charging, thereby increasing the negative electrode potential, avoiding lithium plating caused by excessive polarization, and thus avoiding affecting the fast-charge cycle life of the lithium-ion battery. Therefore, the charging method provided by the present disclosure has the characteristics of fast charging and less impact on the cycle life of the battery compared to the existing technology. In other words, charging with the charging method provided by the present disclosure can extend the cycle life of the battery.

[0053] Optionally, in the first stage, the high-rate current charging method may be:

[0054] Use a constant high-rate current value for constant current charging;

[0055] Alternatively, step-by-step charging is performed at different high-rate current values ​​in different time periods;

[0056] Alternatively, charging is performed at a high rate current value that changes dynamically with charging time.

[0057] It should be noted that there is no special limitation on the high-rate current charging method in the first stage. The purpose of charging in the first stage is mainly to increase the charging rate. As long as fast charging is performed within the limited maximum rate value, it can be used.

[0058] Optionally, in the third stage, constant voltage charging is performed until the rate current is reduced to the charge cut-off current in the following manner:

[0059] (1) Current cut-off, constant voltage charging until the rate current drops to 0.05C;

[0060] Alternatively, (2) the time limit is set, and the constant voltage charging is terminated after a certain time, and the certain time is ≤ 8 minutes (for example, 0.5 minutes, 1 minute, 2 minutes, 3 minutes, 4 minutes, 6 minutes or 8 minutes, etc.).

[0061] It should be noted that, in the third stage, current cutoff has a better effect than time cutoff.

[0062] Furthermore, in order to ensure that the charging method has both high charging efficiency and good polarization elimination effect, the difference between the set voltage value and the cut-off voltage value is 0.15~1.6V (the difference is, for example, 0.15V, 0.5V, 0.8V, 1V, 1.2V, 1.4V or 1.6V, etc.). For example, if the cut-off voltage value is 3.65V, the set voltage value can be 2.05V, 2.5V, 3V, 3.2V, 3.3V, 3.4V or 3.5V, etc.

[0063] Optionally, in order to effectively eliminate the polarization problem caused by the early high-rate charging, the value of the first small-rate current is <1.0C, for example, it can be 0.2C, 0.33C, 0.4C, 0.5C, 0.6V, 0.8C or 0.9C, etc., and the value of the second small-rate current is <1.0C, for example, it can be 0.2C, 0.33C, 0.4C, 0.5C, 0.6V, 0.8C or 0.9C, etc.

[0064] Optionally, in order to ensure charging efficiency, the charging operations from the first stage to the third stage are performed at least once until the battery's state of charge is close to 30-98% (for example, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 92%, 95%, 96% or 98%), preferably 93-98% (for example, 93%, 95%, 96% or 98%), and then the fourth stage charging is performed.

[0065] Optionally, the charging operation from the first stage to the third stage is performed once. During the first stage charging process, a high rate current is used to charge to a state of charge of 50-80% (for example, 50%, 60%, 70% or 80%).

[0066] Alternatively, the charging operation from the first stage to the third stage is performed twice;

[0067] In the first stage of charging, a high rate current is used to charge the battery to a state of charge of 30% to 50% (e.g., 30%, 40%, or 50%).

[0068] During the second first stage charging process, a high rate current is used to charge the battery to a state of charge of 50-80% (eg, 50%, 60%, 70% or 80%).

[0069] It should be noted that, in addition to the above-mentioned one and two operation times, in other embodiments of the present disclosure, the charging operations from the first stage to the third stage can also be repeated three times, four times, five times, etc.

[0070] Optionally, the charge cut-off current in the fourth stage is 0.02C to 0.05C (eg, 0.02C, 0.03C, 0.04C or 0.05C).

[0071] The disclosed embodiment also provides the above-mentioned charging method for application in charging a fast-charging battery.

[0072] Optionally, the fast-charging battery is a ternary lithium-ion battery, a lithium cobalt oxide lithium-ion battery, a lithium iron phosphate lithium-ion battery, a lithium manganese oxide lithium-ion battery or a manganese iron phosphate lithium-ion battery.

[0073] Example 1

[0074] A 3C fast-charging lithium iron phosphate battery is charged using the following steps:

[0075] (1) 3C constant current charging to 80% SOC;

[0076] (2) 0.33C constant current charging to 3.5V;

[0077] (3) 3.5V constant voltage charging, 0.05C cut-off, at this time the charge is 98%;

[0078] (4) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0079] Example 2

[0080] A 3C fast-charging lithium iron phosphate battery is charged using the following steps:

[0081] 1) 3C constant current charging to 80% SOC;

[0082] (2) 0.33C constant current charging to 3.5V

[0083] (3) 3.5V constant voltage charging for 2 minutes, at which time the charge is 93%;

[0084] (4) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0085] Example 3

[0086] A 3C fast-charging lithium iron phosphate battery is charged using the following steps:

[0087] (1) 3C constant current charging to 50% SOC;

[0088] (2) 0.33C constant current charging to 3.4V;

[0089] (3) 3.4V constant voltage charging, 0.05C cut-off;

[0090] (4) 3C constant current charging to 80% SOC;

[0091] (5) 0.33C constant current charging to 3.5V;

[0092] (6) 3.5V constant voltage charging, 0.05C cut-off, at this time the charge is 98%;

[0093] (7) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0094] Example 4

[0095] A 3C fast-charging lithium iron phosphate battery is charged using the following steps:

[0096] (1) 3C constant current charging to 50% SOC;

[0097] (2) 0.33C constant current charging to 3.4V;

[0098] (3) 3.4V constant voltage charging for 2 minutes;

[0099] (4) 3C constant current charging to 80% SOC;

[0100] (5) 0.33C constant current charging to 3.5V;

[0101] (6) 3.5V constant voltage charging for 2 minutes, at which time the charge is 93%;

[0102] (7) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0103] Example 5

[0104] A 2.5C fast-charging lithium iron phosphate battery is charged using the following steps:

[0105] (1) 2.0C constant current charging to 5% SOC, 3.6C constant current charging to 30% SOC, 3.2C charging to 40% SOC, 2.8C charging to 50% SOC, 2.4C constant current charging to 60% SOC, 2.0C charging to 70% SOC, 1.5C charging to 80% SOC. The above average 2.5C step combination charging from 0% SOC to 80% SOC;

[0106] (2) 0.33C constant current charging to 3.5V;

[0107] (3) 3.5V constant voltage charging, 0.05C cut-off, at this time the charge is 98%;

[0108] (4) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0109] Example 6

[0110] A 2.5C fast-charging lithium iron phosphate battery is charged using the following steps:

[0111] (1) 2.0C constant current charging to 5% SOC, 3.6C constant current charging to 30% SOC, 3.2C charging to 40% SOC, 2.8C charging to 50% SOC, 2.4C constant current charging to 60% SOC, 2.0C charging to 70% SOC, 1.5C charging to 80% SOC. The above average 2.5C step combination charging from 0% SOC to 80% SOC;

[0112] (2) 0.33C constant current charging to 3.5V;

[0113] (3) 3.5V constant voltage charging for 2 minutes, at which time the charge is 93%;

[0114] (4) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0115] Example 7

[0116] A 2.5C fast-charging lithium iron phosphate battery is charged using the following steps:

[0117] (1) 0.8C constant current charging to 5% SOC, 3.6C constant current charging to 30% SOC, 3.2C charging to 40% SOC, 2.8C charging to 50% SOC. The above average 2.5C step combination method is used to charge from 0% SOC to 50% SOC;

[0118] (2) 0.33C constant current charging to 3.4V;

[0119] (3) 3.4V constant voltage charging, 0.05C cut-off;

[0120] (4) 3C constant current charging to 80% SOC;

[0121] (5) 0.33C constant current charging to 3.5V;

[0122] (6) 3.5V constant voltage charging, 0.05C cut-off, at this time the charge is 98%;

[0123] (7) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0124] Example 8

[0125] A 2.5C fast-charging lithium iron phosphate battery is charged using the following steps:

[0126] (1) 0.8C constant current charging to 5% SOC, 3.6C constant current charging to 30% SOC, 3.2C charging to 40% SOC, 2.8C charging to 50% SOC. The above average 2.5C step combination method is used to charge from 0% SOC to 50% SOC;

[0127] (2) 0.33C constant current charging to 3.4V;

[0128] (3) 3.4V constant voltage charging for 2 minutes;

[0129] (4) 3C constant current charging to 80% SOC;

[0130] (5) 0.33C constant current charging to 3.5V;

[0131] (6) 3.5V constant voltage charging for 2 minutes, at which time the charge is 93%;

[0132] (7) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0133] Comparative Example 1

[0134] A 3C fast-charging lithium iron phosphate battery is charged using the following steps:

[0135] (1) 3C constant current charging to 80% SOC;

[0136] (2) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0137] Comparative Example 2

[0138] A 2.5C fast-charging lithium iron phosphate battery is charged using the following steps:

[0139] (1) 2.0C constant current charging to 5% SOC, 3.6C constant current charging to 30% SOC, 3.2C charging to 40% SOC, 2.8C charging to 50% SOC, 2.4C constant current charging to 60% SOC, 2.0C charging to 70% SOC, 1.5C charging to 80% SOC. The above average 2.5C step combination charging from 0% SOC to 80% SOC;

[0140] (2) Charge at 0.33C constant current to 3.65V, then charge at 3.65V constant voltage to 0.05C cutoff.

[0141] Experimental example

[0142] Charging is performed according to the charging methods provided in the above-mentioned embodiments and comparative examples.

[0143] After charging, the batteries were uniformly allowed to rest for 30 minutes. Discharge was performed using a 0.33C constant current with a cutoff of 2.0V. After discharge, the batteries were allowed to rest for 30 minutes, and the charge and discharge steps were repeated. The negative electrode potential, maximum surface temperature, and cycle life were measured during the charge and discharge process. The results are recorded in Table 1.

[0144] Table 1 Cycle life of each embodiment and comparative example

[0145] It can be seen from Table 1 that constant voltage charging is set during the charging process of Examples 1-8. Compared with the conventional fast charging method of Comparative Examples 1 and 2, the negative electrode potential of the battery is higher than 0V, which is significantly improved, which can improve the polarization accumulation caused by high-rate fast charging, avoid the negative electrode potential being close to or lower than the lithium deposition potential, and lithium deposition inside the battery, thereby inhibiting the occurrence of side reactions and the rapid consumption of the electrolyte, and improving the cycle life; compared with the comparative example, the surface temperature of the battery cell during charging in each embodiment is lower than 30°C, and the charging is maintained at the optimal operating temperature of the lithium-ion battery; and taking the 3C battery as an example, the 25°C cycle life of each embodiment provided in the present disclosure is more than 1900 times, which is greatly improved compared to 1500 times in Comparative Example 1; in addition, it can be seen from Table 1 that the current cutoff of 0.05C used in Example 1, Example 3, Example 5 and Example 7 is better than the time cutoff of 2min.

[0146] Therefore, the charging method proposed in the present disclosure can significantly improve the cycle life of the battery without affecting the fast charging experience, and can be used on a large scale in the market.

[0147] The above are merely preferred embodiments of the present disclosure and are not intended to limit the present disclosure. Those skilled in the art will readily appreciate that various modifications and variations of the present disclosure are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present disclosure shall be included within the scope of protection of the present disclosure. Industrial Applicability

[0148] The charging method provided by the present disclosure includes a constant voltage charging process after high-rate current charging. This process can eliminate or improve the polarization problem accumulated during the previous high-rate current charging process, increase the negative electrode potential, and avoid lithium deposition caused by excessive polarization, thereby preventing the impact on the fast-charge cycle life of the lithium-ion battery. Therefore, the charging method provided by the present disclosure has the characteristics of fast charging and less impact on the cycle life of the battery compared to the existing technology. In other words, charging with the charging method provided by the present disclosure can extend the cycle life of the battery.

Claims

1. A charging method, characterized in that: It consists of the following consecutive stages: The first stage: charging with high rate current; The second stage: using the first small rate current constant current charging to the set voltage; The third stage: constant voltage charging using the set voltage; Performing the charging operations from the first stage to the third stage at least once; The fourth stage: using the set voltage as the starting voltage, using the second small rate current constant current charging until the voltage rises to the cut-off voltage of the battery, and then using the cut-off voltage to perform constant voltage charging until the rate current decreases to the charging cut-off current; The value range of the high rate current is: 1C≤the high rate current≤the maximum rate charging current allowed by the battery; The values ​​of the first low-rate current and the second low-rate current are smaller than the value of the high-rate current; The set voltage has a value smaller than the cut-off voltage.

2. The charging method according to claim 1, characterized in that: The value of the first low rate current is less than 1.0C.

3. The charging method according to claim 1 or 2, characterized in that: The value of the second small rate current is less than 1.0C.

4. The charging method according to any one of claims 1 to 3, characterized in that: The charging operation from the first stage to the third stage is performed at least once until the state of charge of the battery is 30-98%, and then the fourth stage of charging is performed.

5. The charging method according to any one of claims 1 to 4, characterized in that: The charging operation from the first stage to the third stage is performed at least once until the state of charge of the battery is 93-98%, and then the fourth stage of charging is performed.

6. The charging method according to any one of claims 1 to 5, characterized in that: The difference between the set voltage and the cut-off voltage is 0.15 to 1.6V.

7. The charging method according to any one of claims 1 to 6, characterized in that: In the third stage, the method of using the set voltage for constant voltage charging is: (1) Current cut-off: constant voltage charging is performed until the rate current decreases to the charge cut-off current and then the charging is cut off; Alternatively, (2) the charging is terminated after a certain period of time, wherein the constant voltage charging is terminated, and the certain period of time is ≤8 minutes.

8. The charging method according to claim 7, characterized in that: The charging cut-off current is 0.05C.

9. The charging method according to any one of claims 1 to 8, characterized in that: The charging cut-off current in the fourth stage is 0.02-0.05C.

10. The charging method according to any one of claims 1 to 9, characterized in that: In the first stage, the high rate current charging method is: Use a constant high-rate current value for constant current charging; Alternatively, step-by-step charging is performed at different high-rate current values ​​in different time periods; Alternatively, charging is performed at a high rate current value that changes dynamically with the charging time.

11. The charging method according to any one of claims 1 to 10, characterized in that: The charging operation from the first stage to the third stage is performed once. During the charging process of the first stage, the high rate current is used to charge until the state of charge is 50-80%.

12. The charging method according to any one of claims 1 to 11, characterized in that: The charging operation from the first stage to the third stage is performed twice; In the first stage of charging, the high rate current is used to charge until the state of charge is 30-50%. During the second charging process of the first stage, the high rate current is used to charge until the state of charge is 50% to 80%.

13. Application of the charging method according to any one of claims 1 to 12 in charging a fast-charging battery.

14. The use according to claim 13, characterized in that The fast-charging battery is a ternary lithium-ion battery, a lithium cobalt oxide lithium-ion battery, a lithium iron phosphate lithium-ion battery, a lithium manganese oxide lithium-ion battery or a lithium manganese iron phosphate lithium-ion battery.

15. The use according to claim 13, characterized in that: The fast-charging battery is a 3C fast-charging lithium iron phosphate battery or a 2.5C fast-charging lithium iron phosphate battery.

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