Discharging method of battery and lithium ion battery
By introducing a large-scale discharge step into the discharge method of lithium-ion batteries, the problems of polarization and lithium-ion batteries during fast charging are solved, the battery capacity and cycle life are improved, and safety hazards are reduced.
Patent Information
- Application Number
- CN202510052385.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-01-13
- Publication Date
- 2025-04-22
AI Technical Summary
Lithium-ion batteries are easily polarized during fast charging, resulting in the precipitation of lithium single mass, reducing battery capacity and increasing safety hazards.
A discharge method is adopted, including discharging the lithium-ion battery to a first cutoff condition based on the first magnification, and then discharging to a second cutoff condition based on the second magnification. The first ratio is greater than the second ratio, which improves lithium extraction problems through large-scale discharge, improves battery capacity and cycle life, and reduces safety hazards.
Activate dead lithium by large-scale discharge, improve lithium extraction phenomenon, improve the capacity and cycle life of lithium-ion batteries, and reduce safety hazards.
Smart Images
Figure CN119864526A_ABST
Abstract
Description
Technical Field
[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a battery discharge method and a lithium-ion battery. Background Art
[0002] With the development of new energy technology, energy storage batteries have developed rapidly. Among them, lithium-ion batteries are widely used due to their high energy density and low failure rate.
[0003] In order to improve the user experience of devices equipped with lithium-ion batteries, the demand for fast charging of lithium-ion batteries is increasing. However, during the fast charging process of lithium-ion batteries, lithium-ion batteries are easily polarized, resulting in the precipitation of lithium from the negative electrode of the lithium-ion battery. During the continuous use of lithium-ion batteries, multiple fast charges will be performed, and multiple fast charges will cause lithium to precipitate continuously and cause the capacity of lithium-ion batteries to decrease. More seriously, it may also cause safety problems. Summary of the invention
[0004] The present application provides a battery discharge method and a lithium-ion battery, which can improve the lithium plating of the lithium-ion battery, reduce the possibility of lithium-ion battery capacity reduction, and even cause safety problems.
[0005] In a first aspect, the present application provides a battery discharge method, the discharge method comprising: discharging the lithium-ion battery to a first cutoff condition based on a first rate, and discharging the lithium-ion battery to a second cutoff condition based on a second rate.
[0006] The first rate is greater than the second rate, and the second rate is the discharge rate of the lithium-ion battery in a working state.
[0007] Thus, for a lithium-ion battery, before it works normally, the lithium-ion battery can be discharged based on the first rate. The first rate is greater than the second rate when the lithium-ion battery works normally, so the discharge rate is relatively large during the discharge process before the lithium-ion battery works normally. The large rate of discharge can improve the lithium plating problem of the lithium-ion battery, increase the capacity of the lithium-ion battery, increase the cycle life of the lithium-ion battery, and reduce the possibility of safety hazards of the lithium-ion battery.
[0008] Optionally, the discharge current at the first rate is A1, satisfying: 1C≤A1≤3C.
[0009] In this way, when the lithium-ion battery is discharged based on the first rate, it can be discharged quickly at a large rate, which is easy to activate the dead lithium and improve the lithium precipitation phenomenon.
[0010] Furthermore, it can also reduce the possibility that the lithium-ion battery is discharged too quickly, resulting in insufficient voltage or power of the lithium-ion battery, which may affect the subsequent use of the lithium-ion battery.
[0011] Optionally, the first cutoff condition is to discharge the lithium-ion battery for a preset time period T, wherein the preset time period T satisfies: 1 min ≤ T ≤ 10 min.
[0012] That is, the process of discharging the lithium-ion battery based on the first rate can continue for a preset time period T, so that after the discharge, the remaining power in the lithium-ion battery can meet certain conditions.
[0013] Optionally, the lithium-ion battery has a rated capacity RC, satisfying: A1*T≤10%*RC.
[0014] In this way, the remaining power of the lithium-ion battery after discharge based on the first rate can be controlled to reduce the possibility of excessive discharge, resulting in insufficient power during subsequent normal operation of the lithium-ion battery, which affects the normal operation of the device.
[0015] Optionally, the lithium-ion battery has a discharge cut-off voltage, and the second cut-off condition is that the voltage of the lithium-ion battery reaches the discharge cut-off voltage.
[0016] At this time, the lithium-ion battery can discharge normally to provide power to the device equipped with the lithium-ion battery and ensure the normal operation of the device.
[0017] Optionally, before discharging the lithium-ion battery to the first cutoff condition based on the first rate, the discharge method further includes charging the lithium-ion battery to a third cutoff condition based on a third rate.
[0018] That is, before the lithium-ion battery is discharged based on the first rate, the lithium-ion battery is also charged so that the lithium-ion battery has sufficient power.
[0019] Optionally, in the process of charging the lithium-ion battery to the third cutoff condition based on the third rate, the charging method of the lithium-ion battery is constant current and constant voltage charging.
[0020] The lithium-ion battery has a charge cut-off voltage. The third cut-off condition is that the voltage of the lithium-ion battery reaches the charge cut-off voltage and the charging current is 0.05C.
[0021] Through the above arrangement, the lithium-ion battery can be charged and the possibility of damage caused by overcharging of the lithium-ion battery can be reduced, thereby ensuring the safety of the lithium-ion battery and extending its service life.
[0022] Optionally, the charging current at the third rate is A2, satisfying: 1.5C≤A2≤5C.
[0023] In this way, the lithium-ion battery is charged at a high rate, i.e., fast charging. This can increase the charging speed of the lithium-ion battery, reduce the waiting time of the user during the charging process, and improve the user experience.
[0024] Optionally, after charging the lithium-ion battery to a third cutoff condition based on the third rate and before discharging the lithium-ion battery to a first cutoff condition based on the first rate, the discharging method further includes leaving the lithium-ion battery to a preset condition.
[0025] In this way, the polarization phenomenon during the charging process of the lithium-ion battery can be reduced, so that the voltage of the lithium-ion battery reaches a balance, and the lithium-ion battery has better performance in the subsequent discharge process.
[0026] In a second aspect, the present application provides a lithium-ion battery, which is discharged using the discharge method provided in the first aspect.
[0027] The beneficial effects of the lithium-ion battery provided in the second aspect and each possible design of the second aspect can refer to the beneficial effects brought about by the first aspect and each possible implementation method of the first aspect, which will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 This is a flow chart of a discharge method according to an embodiment of the present application.
[0029] Figure 2 This is a flow chart of another discharging method according to an embodiment of the present application.
[0030] Figure 3 4 is a discharge curve diagram of a lithium-ion battery in an embodiment of the present application.
[0031] Figure 4 It is a discharge curve diagram of a lithium-ion battery in the related art. DETAILED DESCRIPTION
[0032] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusions.
[0034] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.
[0035] The term "and / or" in this article is only a description of the association relationship of the associated objects, indicating that there can be three relationships. For example, A and / or B can mean: A exists, A and B exist at the same time, and B exists. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.
[0036] In addition, the terms "first", "second", etc. in the specification and claims of this application or the above-mentioned drawings are used to distinguish different objects rather than to describe a specific order, and may explicitly or implicitly include one or more of the features.
[0037] In the description of the present application, unless otherwise specified, "plurality" means more than two (including two), and similarly, "multiple groups" means more than two groups (including two).
[0038] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense. For example, the "connected" or "connected" of a circuit structure can refer to not only a physical connection, but also an electrical connection or a signal connection. For example, it can be a direct connection, that is, a physical connection, or it can be an indirect connection through at least one intermediate element, as long as the circuit is connected, and it can also be the internal connection of two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0039] It should be understood that the references to "one embodiment" or "an embodiment" throughout the specification mean that the specific features, structures, or characteristics associated with the embodiment are included in at least one embodiment of the present application. Therefore, the references to "in one embodiment" or "in an embodiment" appearing throughout the specification do not necessarily refer to the same embodiment. In addition, these specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.
[0040] With the development of new energy technology, energy storage batteries have developed rapidly, especially lithium-ion batteries, which have been widely used in recent years due to their advantages such as high energy density and low failure rate.
[0041] For example, lithium-ion batteries, as a power source, are now widely used in new energy vehicles, electric bicycles, laptops, mobile phones and other electrical equipment to provide electrical energy for these electrical equipment to maintain their normal operation.
[0042] Lithium-ion batteries mainly rely on the movement of lithium ions between the positive and negative electrodes to work. When a lithium-ion battery is charged, lithium ions are extracted from the positive electrode, diffused in the electrolyte to the surface of the negative electrode, and embedded in the negative electrode, and the opposite is true when discharging.
[0043] Among them, there are some abnormal situations in the process of charging lithium-ion batteries, such as insufficient lithium embedding space in the negative electrode, too much resistance for lithium ions to embed in the negative electrode, too fast lithium ions to be de-embedded from the positive electrode but unable to embed in the negative electrode in equal amounts, etc. At this time, the lithium ions that cannot be embedded in the negative electrode can only obtain electrons on the surface of the negative electrode, thus forming silvery white metallic lithium (dead lithium), forming lithium precipitation phenomenon.
[0044] The precipitation of lithium means that the number of active lithium ions available for charging and discharging is reduced, which will reduce the capacity of lithium-ion batteries. In addition, the precipitation of lithium may pierce the diaphragm, causing a short circuit inside the lithium-ion battery, which may lead to safety hazards such as thermal runaway, combustion or explosion.
[0045] One of the reasons for lithium plating is the fast charging technology used to charge lithium-ion batteries.
[0046] Fast charging technology can quickly replenish the power of lithium-ion batteries in a shorter period of time, allowing electrical equipment equipped with lithium-ion batteries to quickly return to a usable state and reduce user waiting time.
[0047] However, due to the high charging rate during fast charging, the negative electrode will not be able to quickly complete the lithium insertion, causing lithium precipitation. And as the lithium-ion battery is repeatedly charged and discharged during use, lithium is continuously precipitated, which will continue to aggravate the decrease in the capacity of the lithium-ion battery, increasing the safety risks of the lithium-ion battery.
[0048] Based on the above problems, the embodiments of the present application provide a battery discharge method and a lithium-ion battery.
[0049] like Figure 1 As shown, an embodiment of the present application provides a battery discharging method, comprising the following steps.
[0050] Step 101: Discharge the lithium-ion battery to a first cutoff condition based on a first rate.
[0051] In this embodiment, before the lithium-ion battery operates normally, the lithium-ion battery can be discharged at a first rate as a discharge rate. At this time, inside the lithium-ion battery, lithium ions migrate from the negative electrode to the positive electrode and output current to the outside, so that the chemical energy in the lithium-ion battery gradually decreases.
[0052] Step 102: Discharge the lithium-ion battery to a second cutoff condition based on a second rate.
[0053] The first rate is greater than the second rate, and the second rate is the discharge rate of the lithium-ion battery in a working state.
[0054] Since the second rate is the discharge rate of the lithium-ion battery in the working state, the lithium-ion battery is in a normal working state in step 102. At this time, the lithium-ion battery can discharge normally to provide power to the electrical equipment equipped with the lithium-ion battery to ensure the normal operation of the electrical equipment.
[0055] In this application, the normal operation of a lithium-ion battery means that the lithium-ion battery discharges at an appropriate rate under specified conditions and outputs current to meet the power demand of electrical equipment. For example, when the lithium-ion battery is the power source in a new energy vehicle, the normal operation of the lithium-ion battery means that the lithium-ion battery is installed in the new energy vehicle and the new energy vehicle is running normally.
[0056] When the lithium-ion battery is operating normally, the lithium-ion battery may be in a working state, and at this time, the discharge rate of the lithium-ion battery is the second rate.
[0057] The first rate is greater than the second rate when the lithium-ion battery is working normally. Therefore, the discharge rate in the discharge process before the lithium-ion battery is working normally is larger. Therefore, compared with the discharge process when the lithium-ion battery is working normally, the discharge process of the lithium-ion battery in the manner proposed in step 101 is a fast discharge process.
[0058] When lithium-ion batteries are discharged quickly, if there is dead lithium at the negative electrode, the dead lithium will produce dynamic polarization under the action of the electric field.
[0059] Specifically, there is an electric field in the electrolyte. After repeated charging, the dead lithium produces dynamic polarization under the action of the electric field. During the charging process, lithium ions move from the positive electrode to the negative electrode, and the side of the dead lithium close to the positive electrode becomes negative due to the overpotential, resulting in lithium deposition. The side of the dead lithium close to the negative electrode becomes positive due to the overpotential, resulting in lithium dissolution. That is, the dead lithium will evolve toward the positive electrode during charging. On the contrary, the dead lithium will evolve toward the negative electrode during discharge.
[0060] This dynamic polarization phenomenon makes the dead lithium have a certain activity under the action of the electric field, which can establish electrical contact between the dead lithium and the current collector, thereby achieving activation.
[0061] In summary, a higher discharge rate can improve the lithium plating problem of lithium-ion batteries. In this way, as the dead lithium is activated, the capacity and cycle life of lithium-ion batteries will be increased, while the possibility of safety hazards in lithium-ion batteries will be reduced.
[0062] It should be noted that the second rate can be set according to the rated capacity of the lithium-ion battery, the usage scenario, etc. For example, for a lithium-ion battery with a rated capacity of 5 ampere hours (Ampere Hour, Ah) installed in a new energy vehicle, the discharge current at the second rate of the lithium-ion battery can be 1 rate (Capacity, C).
[0063] The embodiment of the present application does not specifically limit the discharge current of the lithium-ion battery at the second rate.
[0064] In the embodiment of the present application, the discharge current at the first rate is A1, which can satisfy: 1C≤A1≤3C.
[0065] In this way, in step 101, the discharge of the lithium-ion battery can be a high-rate rapid discharge, which is easy to activate the dead lithium and improve the lithium precipitation phenomenon.
[0066] Furthermore, it can also reduce the possibility that the lithium-ion battery is discharged too quickly, resulting in insufficient voltage or power of the lithium-ion battery, which may affect the subsequent use of the lithium-ion battery.
[0067] In lithium-ion batteries, discharge rate = discharge current / rated capacity. The discharge rate can reflect the discharge capacity of lithium-ion batteries and indicates the size of the discharge current. For example, if a battery with a rated capacity of 1000 milliampere hours (mAh) is discharged at a rate of 0.1C, its discharge current is 100 milliamperes (mA).
[0068] In the embodiment of the present application, the discharge current A1 at the first rate may be 1.2C, 1.5C, 2C, 2.5C or 3C, etc., and may be specifically the discharge rate*rated capacity. The embodiment of the present application does not specifically limit the specific value of the discharge current A1 at the first rate.
[0069] Here, in order to make the present application clearer, a lithium-ion battery with a rated capacity of 5Ah is taken as an example for specific description.
[0070] When the discharge current A1 at the first rate is 1C, the current is specifically 5 amperes (Ampere, A). When the discharge current A1 at the first rate is 1.5C, the current is specifically 7.5A. When the discharge current A1 at the first rate is 2C, the current is specifically 10A. Here, no more examples are given.
[0071] In some embodiments, the first cut-off condition is discharging the lithium-ion battery for a preset time period T.
[0072] That is, the process of discharging the lithium-ion battery based on the first rate can continue for a preset time period T, so that after discharging according to the method provided in step 101, the remaining power in the lithium-ion battery can meet certain conditions.
[0073] By setting the preset time length T as described above, the process of rapidly discharging the lithium-ion battery can achieve a better activation effect on the dead lithium, thereby reducing the possibility that the activation effect on the dead lithium is poor due to the short discharge time in step 101. At the same time, the possibility that the discharge time in step 101 is long, resulting in insufficient remaining power in the lithium-ion battery, can also be reduced, thereby reducing the possibility that the normal operation of the subsequent lithium-ion battery is affected.
[0074] In the present application, the preset duration T can be 1 minute (min), 2 min, 3.5 min, 6 min, 8 min, 10 min, etc.
[0075] In the present application, the preset time length T satisfies: 1min≤T≤10min. The specific value of the preset time length T is not specifically limited in the present embodiment.
[0076] It should be noted that the discharge current A1 at the first rate and the preset time length T cooperate with each other to control the remaining power in the lithium-ion battery after the lithium-ion battery is discharged in step 101 .
[0077] Furthermore, the discharge current A1 at the first rate and the preset time duration T are both related to the rated capacity RC of the lithium-ion battery. Specifically, the product of the discharge current A1 at the first rate and the preset time duration T does not exceed 10% of the rated capacity RC of the lithium-ion battery, that is, A1*T≤10%*RC.
[0078] In this way, after the lithium-ion battery is discharged in step 101, the remaining power in the lithium-ion battery can be relatively large, which can reduce the possibility that the remaining power in the lithium-ion battery will affect the subsequent use of the lithium-ion battery.
[0079] In the embodiment of the present application, A1*T≤10%*RC. The value of A1*T may be 10%*RC, 9.5%*RC, 9%*RC, 8.7%*RC or 8%*RC, etc., and may be set according to the actual situation of the lithium-ion battery.
[0080] Through the above settings, the remaining power of the lithium-ion battery after discharge based on the first rate can be controlled, reducing the possibility of excessive discharge in step 101, resulting in insufficient power during subsequent normal operation of the lithium-ion battery, and affecting the normal operation of electrical equipment.
[0081] In the present application, the lithium-ion battery has a discharge cut-off voltage. Based on this, in step 102, the second cut-off condition may be that the voltage of the lithium-ion battery reaches the discharge cut-off voltage.
[0082] When the lithium-ion battery is discharged at the second rate, as the lithium-ion battery continuously outputs electrical energy, the voltage of the lithium-ion battery will gradually decrease.
[0083] When the voltage of the lithium-ion battery reaches the discharge cut-off voltage, the discharge is stopped, which can reduce the possibility of over-discharging of the lithium-ion battery, causing irreversible chemical reactions inside the lithium-ion battery, thereby damaging the lithium-ion battery and shortening the life of the lithium-ion battery.
[0084] Here, a lithium-ion battery with a rated capacity of 5A and a discharge cut-off voltage of 2.0V is used as an example for description. In step 102, the discharge is stopped when the voltage of the lithium-ion battery reaches 2.0V, thereby reducing the possibility of over-discharge.
[0085] It should be noted that different lithium-ion batteries may have different discharge cut-off voltages, and the specific value of the discharge cut-off voltage is not specifically limited in the present embodiment.
[0086] In some embodiments, the present application also provides Figure 2 The battery discharge method shown.
[0087] Step 200: charging the lithium-ion battery to a third cutoff condition based on a third rate.
[0088] At this time, inside the lithium-ion battery, lithium ions can be deintercalated from the positive electrode and migrate to the negative electrode. At the same time, electrons can flow from the positive electrode to the negative electrode through an external circuit to charge the lithium-ion battery.
[0089] Step 201: Discharge the lithium-ion battery to a first cut-off condition based on a first rate.
[0090] For the specific description of step 201, please refer to the above description of step 101, and the embodiment of the present application will not be repeated here.
[0091] Step 202: Discharge the lithium-ion battery to a second cutoff condition based on a second rate.
[0092] For the specific description of step 202, please refer to the above description of step 102, and the embodiment of the present application will not be repeated here.
[0093] In some embodiments, the charging current at the third rate is A2, satisfying: 1.5C≤A2≤5C.
[0094] The charging rate can reflect the speed of charging of lithium-ion batteries. Charging rate = charging current / rated capacity. For example, if a battery with a rated capacity of 1000mAh is charged at a rate of 0.1C, its charging current is 100mA.
[0095] In the embodiment of the present application, 1.5C≤A2≤5C. In this way, the charging of the lithium-ion battery is a high-rate charging, i.e., fast charging. This can reduce the waiting time of the user during the charging process, improve the user's experience, and reduce the possibility of reducing the performance of the lithium-ion battery when the third rate is too large.
[0096] However, according to the above analysis, when lithium-ion batteries are fast charged, lithium-ion batteries are prone to lithium plating problems.
[0097] Therefore, in the present application, after the lithium-ion battery is fast charged, the lithium-ion battery can be discharged at a high rate based on step 201. Based on this, the dead lithium generated by the lithium-ion battery during the charging process can be activated to improve the lithium deposition of the lithium-ion battery.
[0098] In summary, in the embodiments of the present application, after charging the lithium-ion battery, a process of discharging based on the first rate is added, which can improve the lithium plating condition of the lithium-ion battery.
[0099] Moreover, when charging lithium-ion batteries, fast charging can still be used, which can improve lithium plating while taking into account the charging speed of lithium-ion batteries, reduce the user's waiting time during the charging process, and improve the user experience.
[0100] It should be noted that the charging current A2 at the third rate can specifically be 1.5C, 2C, 2.5C, 3C, 5C, etc. The specific value of the charging current A2 at the third rate is not specifically limited in the embodiment of the present application.
[0101] In the related art, in order to reduce the lithium plating phenomenon caused by fast charging, the charging strategy is generally changed. For example, multiple small current charges are added during the charging process, or multiple static steps are added during the charging process.
[0102] In this way, on the one hand, the charging steps are increased, and on the other hand, the charging time is increased and the user experience is reduced during the charging process of repeatedly performing multiple small current charges or adding multiple static steps during the charging process.
[0103] Unlike the related art, the embodiment of the present application can still use traditional fast charging for charging, and adds a high-rate discharge step after charging, which can improve the lithium plating phenomenon caused by fast charging, simplify the charging and discharging steps of lithium-ion batteries, and greatly reduce the user's waiting time.
[0104] Here, in order to make the difference between the battery discharge method proposed in this application and the discharge method in the related art clearer, reference can be made to Figure 3 and Figure 4 Provide specific instructions.
[0105] like Figure 3 As shown, a discharge curve diagram of a lithium-ion battery when it is discharged using the discharge method of the battery proposed in the embodiment of the present application is shown. In the figure, the ordinate is the voltage (Volt, V) of the lithium-ion battery, and the abscissa is the state of charge (State of Charge, SOC) of the lithium-ion battery, specifically the ratio of the discharge amount of the lithium-ion battery to the total capacity of the lithium-ion battery.
[0106] refer to Figure 3 It can be seen that at the beginning of discharge, the voltage of the lithium-ion battery drops from 3.4V to 3.1V. When the ratio of the discharge amount of the lithium-ion battery to the total capacity of the lithium-ion battery is between 0 and 10%, the lithium-ion battery is discharged based on the first rate. When the ratio of the discharge amount of the lithium-ion battery to the total capacity of the lithium-ion battery is greater than 10% and less than or equal to 100%, the lithium-ion battery is discharged based on the second rate. In addition, at the end of discharge, the remaining power of the lithium-ion battery is small, and the voltage of the lithium-ion battery will drop sharply until it reaches the discharge cut-off voltage.
[0107] When the ratio of the discharge amount of the lithium-ion battery to the total capacity of the lithium-ion battery is 10%, the voltage of the lithium-ion battery is unstable and rises slightly. This reflects the phenomenon that the voltage of the lithium-ion battery rises due to the change of the discharge rate of the lithium-ion battery.
[0108] like Figure 4As shown, a discharge curve diagram of a lithium-ion battery when it is discharged using a discharge method in the related art is shown. During the entire discharge process, the lithium-ion battery is discharged at a discharge rate during normal operation. Similarly, the ordinate in the figure is the voltage of the lithium-ion battery, and the abscissa is the state of charge of the lithium-ion battery, specifically the ratio of the discharge amount of the lithium-ion battery to the total capacity of the lithium-ion battery.
[0109] refer to Figure 4 It can be seen that at the beginning of discharge, the voltage of the lithium-ion battery drops from 3.4V to 3.2V. In the subsequent discharge process, the lithium-ion battery discharges at the same rate. Moreover, at the end of discharge, the remaining power of the lithium-ion battery is small, and the voltage of the lithium-ion battery will drop sharply until it reaches the discharge cut-off voltage.
[0110] contrast Figure 3 and Figure 4 , at the beginning of discharge, Figure 3 The voltage corresponding to the discharge curve shown in FIG. 1 drops faster, which reflects that the discharge rate in this section is larger.
[0111] In the stage where the state of charge corresponding to the discharge curve is between 10% and 100%, Figure 3 The discharge curve in Figure 4 It can be seen that at this stage, the discharge method of the battery proposed in this application and the discharge method in the related art are both based on the discharge rate when the lithium-ion battery is working normally.
[0112] It can be seen that compared with the related art, the battery discharge method proposed in the present application further adds a rapid discharge process before the lithium-ion battery works normally.
[0113] In some embodiments, during the process of charging the lithium-ion battery to the third cut-off condition based on the third rate, the lithium-ion battery is charged by constant current and constant voltage charging.
[0114] The lithium-ion battery has a charge cut-off voltage. The third cut-off condition is that the voltage of the lithium-ion battery reaches the charge cut-off voltage and the charging current is 0.05C.
[0115] That is, in step 200, the charging method for the lithium-ion battery can be constant current constant voltage charging.
[0116] Constant current and constant voltage charging means that during the charging process, the battery is first charged with a constant current. When the battery voltage reaches a predetermined voltage value, it is switched to constant voltage charging. At this time, the charging current gradually decreases until the charging current drops to a predetermined current value.
[0117] In the present application, the lithium-ion battery has a charge cut-off voltage. The charge cut-off voltage is the above-mentioned predetermined voltage value. Different lithium-ion batteries may have different charge cut-off voltages. Here, the specific value of the charge cut-off voltage is not specifically limited in the present application embodiment.
[0118] The above-mentioned predetermined current value can be specifically set according to the applicable usage, parameters, etc. of the lithium-ion battery.
[0119] Generally, in the constant current and constant voltage charging process, 0.05C is the standard current for the lithium-ion battery to be charged and cut off. Therefore, in the present application, the predetermined current value may be 0.05C. This can reduce the possibility of damage caused by overcharging of the lithium-ion battery, ensure the safety of the lithium-ion battery, and extend the service life.
[0120] In some embodiments, after charging the lithium-ion battery to a third cutoff condition based on a third rate and before discharging the lithium-ion battery to a first cutoff condition based on a first rate, the discharge method further includes leaving the lithium-ion battery to a preset condition.
[0121] The above-mentioned step of placing the lithium-ion battery on hold is beneficial to the heat dissipation of the lithium-ion battery, can reduce the problems of the lithium-ion battery, and reduce the possibility of overheating of the lithium-ion battery.
[0122] In the embodiment of the present application, the preset condition refers to the shelf time reaching a preset value. For example, the shelf time can be 5 minutes, 10 minutes, 11 minutes, 20 minutes, etc. The specific value of the shelf time can be set according to the specific parameters of the lithium-ion battery, and the embodiment of the present application does not make any specific limitation here.
[0123] In order to make the method proposed in this application clearer, a lithium-ion battery with a rated capacity of 5Ah and a charge and discharge cut-off voltage of 2.0V-3.8V is used as an example to explain in detail the discharge method of the battery provided in this application, wherein 2.0V is the discharge cut-off voltage and 3.8V is the charge cut-off voltage.
[0124] When charging the lithium-ion battery, firstly, constant current charging is performed based on the charging current A2 at the third rate.
[0125] As charging progresses, the voltage of the lithium-ion battery will gradually rise. When the voltage of the lithium-ion battery reaches 3.8V, it switches to constant voltage charging.
[0126] As charging continues, the charging current of the lithium-ion battery will gradually decrease, and the charging will end when the charging current drops to 0.05C. At this point, the lithium-ion battery is fully charged.
[0127] Afterwards, discharge may be performed based on the charging current A1 at the first rate, and the discharge may last for a preset time period T.
[0128] Afterwards, the lithium-ion battery may be discharged at a second rate until the voltage of the lithium-ion battery reaches 2.0 V, at which point the discharge of the lithium-ion battery is complete.
[0129] In order to make the purpose, technical solution and beneficial effects of the present application clearer, the present invention is further described below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and are not used to limit the scope of the present application.
[0130] Among them, the lithium-ion batteries all have a rated capacity of 5Ah, a charging cut-off voltage of 3.8V, and a discharging cut-off voltage of 2.0V.
[0131] For ease of explanation, the step of charging the lithium-ion battery in step 200 is referred to as a charging step. The step of discharging the lithium-ion battery in step 201 is referred to as a first discharging step, and the step of discharging the lithium-ion battery in step 202 is referred to as a second discharging step.
[0132] Example 1
[0133] (1) Execute the charging step to charge the lithium-ion battery at a charging current of 1.5C until the voltage of the lithium-ion battery reaches 3.8V, and the charging current is 0.05C.
[0134] (2) Leave the lithium-ion battery aside for 10 minutes.
[0135] (3) Perform the first discharge step to discharge the lithium-ion battery at a discharge current of 1.2 C for 5 minutes.
[0136] (4) Execute a second discharging step to discharge the lithium-ion battery at a discharge current of 1C until the voltage of the lithium-ion battery reaches 2.0V.
[0137] (5) Repeat steps (1) to (5) above 100 times.
[0138] The difference between Example 2-3 and Example 1 is that the discharge current and discharge time in step (3) are different. Please refer to Table 1 for details.
[0139] The difference between Example 4 and Example 1 is that the charging current in step (1) is different, and the discharge current and discharge time in step (3) are different. Please refer to Table 1 for details.
[0140] The difference between Example 5 and Example 4 is that the discharge current and discharge time in step (3) are different. Please refer to Table 1 for details.
[0141] The difference between Comparative Example 1 and Example 1 is that step (3) is not used.
[0142] The difference between Comparative Example 2 and Example 4 is that step (3) is not used.
[0143] Table 1
[0144]
[0145] Performance tests were conducted on the above embodiments and comparative examples to test the initial capacity, coulombic efficiency and capacity retention rate of the lithium-ion batteries in each embodiment and comparative example.
[0146] The initial capacity is the capacity Q of the lithium-ion battery obtained by testing before cyclically executing steps (1) to (5) above.
[0147] The coulombic efficiency is the ratio CE of the sum of the discharge capacities in steps (3) and (5) to the charge capacity in step (1) during the current charge and discharge process when the above steps (1) to (5) are cycled 100 times.
[0148] The capacity retention rate is the ratio R of the remaining capacity of the lithium-ion battery to the initial capacity Q after the above steps (1) to (5) are cycled 100 times.
[0149] The performance tests were performed on the lithium-ion batteries of the above embodiments and comparative examples, and their initial capacity, coulombic efficiency and capacity retention rate were recorded, as shown in Table 2.
[0150] Table 2
[0151] Initial capacity Q(Ah) Coulomb efficiency CE Capacity retention rate R Example 1 4.82 102.1％ 91.61％ Example 2 4.82 100.3％ 89.67％ Example 3 4.83 99.2％ 88.21％ Example 4 4.81 101.5％ 87.8％ Example 5 4.82 99.6％ 86.83％ Comparative Example 1 4.84 93.2％ 87.56％ Comparative Example 2 4.80 92.5％ 85.32％
[0152] According to the above data, when the first discharge step is added, the coulombic efficiency and capacity retention rate of the lithium-ion battery are improved, and the discharge rate and discharge time in the first discharge step will affect the coulombic efficiency and capacity retention rate of the lithium-ion battery.
[0153] By comparing Example 1, Example 2, Example 3 and Comparative Example 1, or comparing Example 4, Example 5 and Comparative Example 2, it can be seen that when the charging rate is the same, adding a first discharge step after the charging step can improve the coulombic efficiency and capacity retention rate of the lithium-ion battery.
[0154] Furthermore, in Example 1, Example 2 and Example 4, the coulombic efficiency of the lithium-ion battery reaches a value greater than 100%, which also means that the dead lithium deposited on the negative electrode surface of the lithium-ion battery is recovered.
[0155] In addition, the embodiments of the present application further provide a lithium-ion battery, which can be discharged using the discharge method provided in the above embodiments.
[0156] In this way, the lithium plating problem of lithium-ion batteries can be improved, the capacity of lithium-ion batteries can be increased, and the possibility of safety hazards of lithium-ion batteries can be reduced.
[0157] Based on this, in electrical equipment equipped with the above-mentioned lithium-ion battery, the user's experience of using the equipment and the safety when using the electrical equipment can be improved.
[0158] Among them, the electrical equipment equipped with the above-mentioned lithium-ion battery can specifically be new energy vehicles, electric bicycles, laptop computers, mobile phones, etc., and this embodiment of the application does not make specific limitations on this.
[0159] In addition, for lithium-ion batteries that have already had lithium precipitated, the discharge method proposed in the embodiment of the present application can also activate the precipitated lithium, so that the dead lithium can become active again and participate in the charging and discharging process, thereby achieving the effect of restoring the capacity of the lithium-ion battery, thereby increasing the life and cycle number of the lithium-ion battery.
[0160] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, but the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.
Claims
1. A battery discharge method, applied to lithium-ion batteries, characterized in that: The discharge method comprises: Discharging the lithium-ion battery to a first cutoff condition based on a first rate; Discharging the lithium-ion battery to a second cutoff condition based on a second rate; The first rate is greater than the second rate, and the second rate is the discharge rate of the lithium-ion battery in a working state.
2. The discharge method according to claim 1, characterized in that: The discharge current at the first rate is A1, which satisfies: 1C≤A1≤3C.
3. The discharge method according to claim 2, characterized in that: The first cut-off condition is: discharging the lithium-ion battery for a preset time period T, wherein the preset time period T satisfies: 1 min ≤ T ≤ 10 min.
4. The discharge method according to claim 3, characterized in that: The lithium ion battery has a rated capacity RC, which satisfies: A1*T≤10%*RC.
5. The discharge method according to claim 1, characterized in that: The lithium ion battery has a discharge cut-off voltage, and the second cut-off condition is that the voltage of the lithium ion battery reaches the discharge cut-off voltage.
6. The discharge method according to claim 1, characterized in that: Before discharging the lithium-ion battery to a first cut-off condition based on the first rate, the method further includes: The lithium ion battery is charged to a third cutoff condition based on a third rate.
7. The discharge method according to claim 6, characterized in that: In the process of charging the lithium-ion battery to a third cutoff condition based on the third rate, the lithium-ion battery is charged in a constant current and constant voltage manner; The lithium-ion battery has a charge cut-off voltage, and the third cut-off condition is that the voltage of the lithium-ion battery reaches the charge cut-off voltage and the charging current is 0.05C.
8. The discharge method according to claim 6, characterized in that: The charging current at the third rate is A2, which satisfies: 1.5C≤A2≤5C.
9. The discharge method according to claim 6, characterized in that: After charging the lithium ion battery to a third cutoff condition based on the third rate and before discharging the lithium ion battery to a first cutoff condition based on the first rate, the discharging method further includes: The lithium-ion battery is left to a predetermined condition.
10. A lithium ion battery, characterized in that: The lithium-ion battery is discharged using the discharge method described in any one of claims 1 to 9.