Self-adaptive control method and system for discharge of waste lithium battery

Abstract

The invention relates to the technical field of lithium battery recovery processing, and discloses a waste lithium battery discharge self-adaptive control method and system, and the method comprises the steps: connecting a waste lithium battery to a discharge circuit, monitoring the voltage of the battery end in real time, and carrying out the constant-current discharge when the voltage is higher than a first threshold value; and when the monitored voltage is lower than a first threshold value, switching to an adaptive discharge stage, measuring the internal resistance of the battery in real time through an alternating current impedance method in the stage, dynamically adjusting the discharge current by taking the constant heating power as a target, and stopping discharge until the voltage of the battery end reaches a termination condition. According to the method, the problems that an existing discharging method is not safe, not thorough and not environmentally friendly are solved, and safe, efficient and self-adaptive control over the discharging process of the waste lithium battery is achieved.

Description

Technical Field

[0001] This invention relates to the field of lithium battery recycling technology, and more particularly to the discharge control of waste lithium batteries, and more specifically to an adaptive discharge control method and system for waste lithium batteries. Background Technology

[0002] With the widespread use of lithium batteries, safety issues during their recycling process have become increasingly prominent. Thorough and safe discharge of used lithium batteries is a crucial first step in the recycling process. Currently, common discharge methods have many drawbacks: For example, the invention patent with publication number CN108134153A discloses a method for processing waste lithium-ion batteries. Although the method is simple, the salt water discharge process will produce corrosive liquid and harmful gas, causing secondary pollution. In addition, the discharge speed is slow and the efficiency is low.

[0003] For example, the invention patent with publication number CN108682913A discloses a fast discharge device and discharge method for waste square batteries. Although the method discharges relatively thoroughly, it may cause local overheating due to poor contact, which poses a safety hazard. In addition, the discharge medium needs to be separated afterward, which increases the processing cost.

[0004] For example, invention patent CN119447551A discloses a method and system for the tiered recycling and reuse of waste lithium-ion batteries. This method classifies batteries according to their aging level and designs differentiated discharge schemes for different levels, including constant current discharge and pulse discharge. However, this method does not consider the significant increase in battery heat generation caused by the sharp increase in battery internal resistance in the later stages of discharge, resulting in insufficient safety.

[0005] In general, current methods for controlling the discharge of spent lithium batteries do not take into account the electrochemical characteristics that occur when the internal resistance of lithium batteries increases sharply during discharge (low voltage stage). This results in the discharge process being either unsafe (overheating, fire), incomplete (residual charge), or environmentally unfriendly. Summary of the Invention

[0006] To address the problems and shortcomings of the existing technologies, this invention proposes an adaptive discharge control method and system for waste lithium batteries. This solution achieves intelligent discharge control that ensures safe and complete discharge throughout the entire process based on real-time monitoring of the internal resistance of waste lithium batteries. To achieve the above-mentioned objectives, the technical solution of the present invention is as follows: Firstly, this invention proposes an adaptive discharge control method for spent lithium batteries. This method dynamically adjusts the discharge control strategy by real-time monitoring of the internal resistance of the spent lithium batteries. As discharge progresses, the current battery terminal voltage is used as the criterion for stopping the discharge, determining whether the battery should be stopped. This invention achieves a safe, efficient, and thorough discharge process during the recycling and discharge of spent lithium batteries.

[0007] Figure 1 The flowchart of the control method of this invention is shown in the appendix to the specification. Figure 1 As shown, the discharge control method for used lithium batteries specifically includes the following stages: (1) Initialization and voltage monitoring: Connect the waste lithium battery to be processed to the discharge circuit, turn on the voltage monitoring module in the system, and obtain the battery terminal voltage in real time.

[0008] (2) Select the discharge mode based on the monitored battery terminal voltage, including constant current discharge mode and constant heat power discharge mode; (2.1) Constant current discharge: When the battery terminal voltage is detected to be higher than or equal to the first preset voltage threshold (e.g., 2.0V), the discharge circuit is controlled to discharge the battery with a constant current (e.g., a constant current of 0.2C to 2C, preferably 0.5C).

[0009] In this invention, C represents the ratio of the discharge current magnitude, i.e., the rate of discharge. For example, when a battery with a rated capacity of 100Ah is discharged at 20A, its discharge rate is 0.2C.

[0010] (2.2) Adaptive constant heating power discharge: When the battery terminal voltage is detected to be lower than the first preset voltage threshold, the battery is discharged using constant heating power.

[0011] For constant heat power discharge, with the goal of maintaining a constant heat power of the battery, the discharge current of the discharge circuit is dynamically controlled to keep the heat power of the battery at a preset value, and the battery is discharged.

[0012] During the discharge process, based on the real-time measured current internal resistance of the battery and the preset heat generation power value, the current of the discharge circuit is determined and controlled to discharge the waste lithium battery, so that the heat generation power of the battery remains at the preset heat generation power value throughout the discharge process. In other words, the heat generation power of the battery is constant during discharge.

[0013] The specific steps for the adaptive constant power discharge control method are as follows: (3.1) Internal resistance measurement: The internal resistance of the battery is measured in real time using the AC signal injection method; (3.2) Power calculation and control: With the goal of maintaining the constant heat power of the battery, the discharge current of the current circuit is dynamically calculated based on the internal resistance value obtained by real-time measurement and the preset heat power value, and the discharge circuit outputs the corresponding current value so that the heat power (P = I² * R, where I is the circuit discharge current and R is the real-time internal resistance of the battery) is kept at the preset heat power value during the battery discharge process.

[0014] In this invention, considering the different weights of different batteries, the preset heating power value is generally 1-10w / kg for different battery models.

[0015] For the AC signal injection method: a small AC current signal of a specific frequency is injected into the battery through a signal generator, and the AC voltage response at both ends of the battery is detected at the same time. By calculating the ratio of the AC voltage to the AC current, the AC internal resistance of the battery at that frequency is obtained, which is the current internal resistance value of the battery.

[0016] (4) Discharge termination: As the discharge proceeds, the battery terminal voltage decreases continuously and the internal resistance gradually increases. When the battery terminal voltage is detected to drop below the second preset voltage threshold (e.g., 0.5V to 1.0V), the discharge stops.

[0017] In the adaptive discharge control method for waste lithium batteries disclosed in this invention, batteries of different models or with different degrees of aging undergo different discharge processes, mainly determined by their initial state. For example, if the terminal voltage of a waste lithium battery to be processed is initially detected to be lower than a first preset voltage threshold, then a constant heating power discharge mode is directly used to discharge it, and the entire discharge process consists of only one stage. However, for waste lithium batteries whose initial terminal voltage is greater than or equal to the first preset voltage threshold, two stages are required: constant current discharge and constant heating power discharge. The first stage is constant current discharge, and after the terminal voltage is discharged to a value lower than the first preset voltage, the second stage, constant heating power discharge mode, is entered to discharge it.

[0018] Therefore, for waste batteries that have undergone the first and second stages of the waste battery discharge process, the switching control strategy involved is as follows: during the discharge process, the battery's terminal voltage is continuously monitored. When the terminal voltage drops below a first preset voltage threshold, the system switches the discharge control mode from the constant current discharge method of the first stage to the second stage, using constant heating power to discharge the battery. Secondly, based on the same inventive concept, this invention also proposes a waste lithium battery discharge adaptive control system. The control system is used to implement the above-mentioned waste lithium battery discharge adaptive control method, specifically including: The voltage monitoring module is used to monitor the terminal voltage of the used lithium batteries in the discharge circuit in real time. The main control module selects the discharge mode based on the battery's terminal voltage to discharge the used lithium batteries. As discharge progresses, when the battery's terminal voltage falls below a threshold, the discharge circuit stops discharging the battery. The discharge modes include constant current discharge mode and constant heat output discharge mode. The beneficial effects of this invention are: 1. During the discharge process, this invention effectively avoids the risks of overheating and thermal runaway caused by a sharp increase in internal resistance by real-time monitoring of the internal resistance of the spent lithium battery, a key safety indicator, and by adopting a constant power mode in the later stages of discharge. Simultaneously, the dual cutoff conditions of voltage and internal resistance provide multiple safety guarantees throughout the entire discharge control process.

[0019] 2. This invention fully utilizes the discharge characteristics of lithium batteries. In the early stage, a constant current is used for discharge to improve discharge efficiency, and in the later stage, a constant power method is used for discharge. Dynamically controlling the discharge current can deeply release the residual energy of the battery, ensuring complete discharge and providing a safe foundation for subsequent disassembly and recycling.

[0020] 3. The discharge method proposed in this invention is a dry, electrically controlled process that does not introduce any chemical media or generate pollutants, making it more environmentally friendly.

[0021] 4. The discharge control method of the present invention is based on the battery's own state (internal resistance) for feedback control, and adopts different strategies for discharge in stages, which has good adaptability to waste lithium batteries of different models and different aging degrees. Attached Figure Description

[0022] The foregoing and hereinafter detailed description of the invention becomes clearer when read in conjunction with the following drawings, in which: Figure 1 This is a flowchart of the control method of the present invention. Detailed Implementation To enable those skilled in the art to better understand the technical solutions of this invention, several specific embodiments will be used to further illustrate the technical solutions for achieving the objectives of this invention. It should be noted that the technical solutions claimed by this invention include, but are not limited to, the following embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort should fall within the scope of protection of this invention.

[0023] Example 1 This embodiment provides a typical method for discharging spent lithium batteries, specifically for processing 18650 type spent lithium-ion batteries with a nominal capacity of 2000mAh. The specific steps are as follows: (1) Connect the battery to a discharge device that has voltage, current and internal resistance detection functions.

[0024] (2) During device initialization, the system monitors the battery terminal voltage through the voltage monitoring module and measures the initial voltage as 3.2V, which is higher than the first preset voltage threshold of 2.0V.

[0025] (3) The main control module of the system controls the discharge equipment to enter the first discharge stage and discharges the waste lithium battery in the connected equipment with a constant current of 0.5C (i.e. 1000mA).

[0026] (4) When the battery terminal voltage drops to 2.0V in real time, the main control module controls the device to switch to the second discharge stage.

[0027] In the second discharge stage, the system first injects a 1kHz AC small signal into the spent lithium battery to obtain the current internal resistance of 80mΩ. Then, the system control device, aiming to maintain a constant heat output during battery discharge (the preset heat output corresponds to 0.2C, i.e., the power of 400mA current at 2.0V, approximately 0.8W), dynamically adjusts the discharge current according to the formula I = sqrt(P / R) to maintain the battery's heat output at the preset value. At this point, the discharge current is set to sqrt(0.8 / 0.08) ≈ 3.16A (this is a theoretical calculation example; in actual operation, I will dynamically adjust based on the real-time internal resistance R to keep P constant).

[0028] As discharge proceeds, the battery's internal resistance gradually increases to 200mΩ. The system's automatic control equipment then reduces the discharge current to sqrt(0.8 / 0.2) = 2A to maintain the preset 0.8W heating power for discharging the battery.

[0029] (5) When the battery terminal voltage drops to 0.8V, the system determines that the battery has reached the end of the discharge and automatically controls the equipment to stop discharging.

[0030] Example 2 The difference between this embodiment and Embodiment 1 is that the first preset voltage threshold is set to 1.8V, the first constant discharge current is 0.3C in constant current discharge mode, and the preset reference value for heat generation power is 0.5W in constant heat generation power discharge mode. This method is suitable for scenarios with more stringent requirements for temperature rise during discharge, ensuring absolute safety with a more conservative strategy.

[0031] Example 3 The difference between this embodiment and Embodiment 1 is that the initial voltage is lower than the discharge cutoff voltage of the constant current discharge mode, and discharge is only performed through the constant heating power mode. The preset heating power is 0.5W, and the discharge termination condition is that the terminal voltage is less than or equal to 0.5V. This solution is particularly suitable for handling batteries with low initial voltages.

[0032] The discharge termination condition is solely based on the internal resistance threshold. When the battery's internal resistance is detected to rise to 250mΩ, discharge is immediately stopped regardless of the battery terminal voltage. This method is particularly suitable for handling abnormal batteries that may have a minor internal short circuit. The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. An adaptive control method for discharging spent lithium batteries, characterized in that, Includes the following steps: The waste lithium batteries to be processed are connected to the discharge circuit, and the terminal voltage of the batteries is monitored in real time. The discharge mode is selected based on the battery's terminal voltage, including constant current discharge mode and constant heat power discharge mode. Discharge continues until the battery's terminal voltage falls below a threshold, at which point the discharge stops.

2. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, The discharge mode is selected based on the battery's terminal voltage, including: When the current voltage of the battery is detected to be higher than or equal to the first preset voltage threshold, the battery is discharged using a constant current discharge mode. When the current voltage of the battery is detected to be lower than the first preset voltage threshold, the battery is discharged using a constant heating power discharge mode.

3. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, In constant current discharge mode, the control discharge circuit discharges the battery in the circuit with a preset constant current.

4. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, For the constant heat power discharge mode, the goal is to maintain a constant heat power of the battery. The discharge current of the discharge circuit is dynamically controlled to keep the heat power of the battery at the preset value and discharge the battery.

5. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, When the battery enters the constant heating power discharge mode, the current internal resistance of the battery is measured in real time. The discharge current of the circuit is calculated based on the battery internal resistance and the preset heating power value, and the battery is discharged using this discharge current.

6. The adaptive control method for discharging waste lithium batteries according to claim 5, characterized in that, The current internal resistance of the battery is obtained by the AC signal injection method.

7. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, The first preset voltage threshold is 1.8V to 2.2V.

8. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, The first constant current is 0.1C to 2C.

9. The adaptive control method for discharging waste lithium batteries according to claim 1, characterized in that, For the constant heating power discharge mode, the preset heating power value is 1-10w / kg.

10. An adaptive control system for discharging spent lithium batteries, characterized in that, The system is used to implement the adaptive discharge control method for spent lithium batteries as described in any one of claims 1-9, including: The voltage monitoring module is used to monitor the terminal voltage of the used lithium batteries in the discharge circuit in real time. The main control module selects a discharge mode to discharge the waste lithium battery based on the battery's terminal voltage. As the discharge proceeds, when the battery's terminal voltage falls below a threshold, the control circuit stops discharging the battery. The discharge modes include a constant current discharge mode and a constant heat power discharge mode.

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