High-power energy storage device grouping method

Abstract

The invention discloses a high-power energy storage device grouping method in the technical field of energy storage device grouping, which comprises the following steps of: 1, discharging an energy storage device Ni at 1C to a lower use limit, then charging the energy storage device Ni at constant current and constant voltage of 5C to 10C to a charging upper limit, and then measuring the internal resistance Ri of the energy storage device Ni; 2, after the internal resistance is measured, discharging to a lower discharge limit at a large current of more than 10C, and recording a discharge capacity Ci, a voltage Vi-0 at the end of the discharge and a rebound voltage Vi-5 in the 5th second after the end of the discharge; and 3, the internal resistance, the discharge capacity and the rebound voltage are dimensionless, specifically as follows: # imgabs0 #, and {Ri} max ({Ci} max, {Vi-5} max) and {Ri} min ({Ci} min, {Vi-5} min) are respectively the maximum value and the minimum value of the internal resistance Ri (the large-current discharge capacity Ci and the rebound voltage Vi-5) of the energy storage device. And 4, after dimensionless processing, selecting the energy storage devices falling in a certain interval for matching. The method provided by the invention can effectively prolong the cycle life of the assembled energy storage device.

Description

Technical Field

[0001] The invention belongs to the technical field of energy storage device assembly, and in particular relates to a high-power energy storage device assembly method. Background Art

[0002] High-power energy storage devices can be charged at a high rate and output high power, and have a wide range of applications. High-power performance is an important indicator for evaluating high-power energy storage devices, which directly reflects the ability of energy storage devices to accept and provide current. In order to obtain a higher discharge limit voltage and a larger current output, high-power energy storage devices are usually connected in series and parallel to form modules. However, when the module is outputting high power, each energy storage device is discharged at the same time. If the performance of each energy storage device is inconsistent, it will inevitably affect the maximum output power, or the working time at maximum power output will be difficult to meet, which will also affect the ultimate service life of the module.

[0003] At present, the matching of high-power energy storage devices mainly considers the capacity deviation and internal resistance deviation between single energy storage devices in the same module, specifically: the capacity deviation between single energy storage devices in the same module should be within 3%; the internal resistance deviation between single energy storage devices in the same module should be within 5%; the average charge and discharge efficiency of the energy storage device in the second and third weeks of formation is higher than 99%; the 30-day self-discharge rate is less than 5%. However, after the high-power energy storage devices are matched in this way, the effect is not ideal; the specific reason is that the internal resistance of the energy storage device includes ohmic internal resistance and polarization internal resistance, and the internal resistance of the energy storage device increases when the current is discharged. At the same time, the larger the internal resistance, the greater the discharge current, the greater the voltage drop, resulting in a decrease in the output voltage of the energy storage device, thereby reducing its capacity. The relationship between the voltage rebound of the energy storage device after discharge and its internal resistance is mainly reflected in the voltage drop caused by the internal resistance when the energy storage device is discharged and the voltage drop on the internal resistance disappears after the discharge, resulting in a voltage rebound. The longer it takes for the voltage of an energy storage device to rebound after discharge, the more chemical substances that have not completed the reaction inside the energy storage device, and these chemical substances will gradually decompose inside the energy storage device, further reducing its capacity. Therefore, high-power energy storage devices have a high self-discharge rate, and the inconsistency between internal resistance and self-discharge will be accumulated and amplified in high-power modules. Summary of the invention

[0004] The present invention aims to provide a high-power energy storage device assembly method to increase the cycle life of the assembled energy storage device.

[0005] A high-power energy storage device assembly method in this scheme includes the following steps:

[0006] Step 1: Energy storage device N i Discharge at 1C to the lower limit of use, then charge at a high current of 5C~10C constant current and constant voltage to the upper limit of charge, and then measure its internal resistance R i ;

[0007] Step 2: After measuring the internal resistance, discharge the battery to the lower limit with a high current of more than 10C and record the discharge capacity C i , the voltage at the end of discharge is V i-0 , after the end of the 5s rebound voltage V i-5 ;

[0008] Step 3: Non-dimensionalize the internal resistance, discharge capacity and rebound voltage, as follows:

[0009]

[0010] Among them, {R i} max , {R i} min Respectively represent the internal resistance of the energy storage device R i The maximum and minimum values ​​of i} max 、{C i} min Respectively represent the discharge capacity of the energy storage device C i The maximum and minimum values ​​of {V i-5} max , {V i-5} min Represents the rebound voltage V of the energy storage device i-5 The maximum and minimum values ​​of

[0011] Step 4: After dimensionless processing, select energy storage devices that fall within a certain interval for grouping.

[0012] Furthermore, in step 1, the lower limit of use is 2.5 V, and the upper limit of charging is 4.3 V. An LCO capacitor type energy storage device with a nominal capacity of 1.4 Ah is paired.

[0013] Beneficial effects of this application:

[0014] 1. Improve the consistency of grouping: By using high-current charge and discharge tests and measuring key parameters such as internal resistance, discharge capacity and rebound voltage, and non-dimensionalizing these parameters, this method can more accurately evaluate the performance differences of energy storage devices under high-power conditions, thereby selecting energy storage devices with more consistent performance for grouping. This helps to improve the consistency between energy storage devices in the module and reduce power output fluctuations and shortened life due to performance differences.

[0015] 2. Optimize cycle life: Since this method takes into account the internal resistance change, discharge capacity, and voltage rebound of energy storage devices during high current charging and discharging, these characteristics are closely related to the cycle life of energy storage devices. By selecting energy storage devices with consistent performance for grouping, the internal loss of the module at high power output can be reduced, the temperature rise of the energy storage device can be reduced, and the cycle life of the module can be extended.

[0016] 3. Improve module performance: The high-power energy storage device module assembled by this method can output higher power under the same conditions, have more stable voltage output and longer continuous working time. This has important practical significance for energy storage systems that require high power and long-term stable operation.

[0017] 4. Reduce the self-discharge rate: This method helps reduce the self-discharge rate of the module by dimensionless processing and screening energy storage devices with consistent performance. Because the self-discharge rate is closely related to the internal resistance and chemical reaction activity of the energy storage device, energy storage devices with consistent performance can reduce the capacity loss and shortened life caused by inconsistent self-discharge after forming a module.

[0018] 5. Improve system reliability: The high-power energy storage device modules assembled by this method can reduce the risk of failure of the entire module due to single-unit failure because the performance of each energy storage device is consistent. This helps to improve the reliability and stability of the energy storage system and reduce maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A dimensionless curve diagram of the capacity, internal resistance, and rebound voltage of an energy storage device in a high-power energy storage device assembly method according to an embodiment of the present invention;

[0020] Figure 2 This is a comparison chart of the module cycles of the matching groups ① to ③;

[0021] Figure 3 It is a cycle comparison diagram of the matching modules of matching ① to ③ and the matching modules of the conventional method. DETAILED DESCRIPTION

[0022] The following is further described in detail through specific implementation methods:

[0023] Embodiment: A method for assembling a high-power energy storage device comprises the following steps:

[0024] Step 1: Select 156 LCO capacitor energy storage devices (nominal capacity 1.4Ah), energy storage device N i Discharge at 1C to 2.5V, then charge at a high current of 10C constant current and constant voltage to 4.3V, and then measure its internal resistance R i ;

[0025] Step 2: After measuring the internal resistance, discharge the battery with a high current of 20C until the cut-off voltage reaches 2.5V, and record the discharge capacity C i , the voltage at the end of discharge is V i-0 , after the end of the 5s rebound voltage V i-5 ;

[0026] Step 3: Non-dimensionalize the internal resistance, discharge capacity and rebound voltage, as follows:

[0027]

[0028] Among them, {R i} max , {R i} min Respectively represent the internal resistance of the energy storage device R i The maximum and minimum values ​​of i} max 、{C i} min Respectively represent the discharge capacity of the energy storage device C i The maximum and minimum values ​​of {V i-5} max , {V i-5} min Represents the rebound voltage V of the energy storage device i-5 The maximum and minimum values ​​of the dimensionless curve are shown in the attached figure. Figure 1 As shown;

[0029] Step 4. After dimensionless processing, select energy storage devices that fall within a certain range for grouping. When grouping, 5. The range can be divided according to different application requirements, and finally energy storage devices with different performances can be grouped according to different requirements.

[0030] Example 1:

[0031] Matching group ①: Capacity C i The selection interval is [0.2,0.5], the internal resistance R i The selection interval is [0.15, 0.5], and the rebound voltage V at the 5th second i-5 Select energy storage devices with a range of [0.05,0.15]; Group ②: Capacity C i The selection interval is [0.1, 0.5], the internal resistance R i The selection interval is [0.1, 0.5], and the rebound voltage V at the 5th second i-5 Select energy storage devices with a range of [0.18, 0.3]; Group ③: Capacity C i The selection interval is [0.2,0.55], the internal resistance R i The selection interval is [0.25,0.5], and the rebound voltage V at the 5th second i-5Select energy storage devices in the interval [0.25,0.4].

[0032] The module cycle curve of 5 parallel and 8 series composed of combination ① to combination ③ (5C charging, 20C discharging) is as shown in the attached figure. Figure 2 As shown in the figure, the initial cycle capacity of the three modules is basically the same. During the 600 cycles, the module in group ③ decays the slowest (the rebound voltage V i-5 High, slow capacity loss during the cycle), followed by group ② (5s rebound voltage V i-5 The second highest, the capacity loss during the cycle is slow), and the fastest decay in the later stage of the combination ① (5s rebound voltage V i-5 low, and large capacity loss in the later stage of the cycle).

[0033] Example 2:

[0034] Conventional screening and matching method: the capacity deviation between single energy storage devices in the same module should be within 3%; the internal resistance deviation between single energy storage devices in the same module should be within 5%; the average charge and discharge efficiency of the energy storage device in the second and third weeks of formation is higher than 99%; the 30-day self-discharge rate is less than 5%. According to this method, the above 156 LCO capacitor-type energy storage devices were screened for energy storage devices to be matched into 5-parallel and 8-series modules, and the sequential results were compared with the cycle results of the modules matched according to the patent method (matching ① and matching ②). The comparison results are shown in the attached Figure 3 ,Depend on Figure 3 It can be seen that, for the same 600 cycles, the patented combination method is superior. Figure 3 In the patent method matching module 1 and the patent method matching module 2 are assigned to matching group ① and matching group ② respectively.

[0035] The above is only an embodiment of the present invention, and the common knowledge such as the known specific structure and characteristics in the scheme is not described in detail here. It should be pointed out that for those skilled in the art, several deformations and improvements can be made without departing from the structure of the present invention, which should also be regarded as the protection scope of the present invention, and these will not affect the effect of the implementation of the present invention and the practicality of the patent. The scope of protection required by this application shall be based on the content of its claims, and the specific implementation methods and other records in the specification can be used to interpret the content of the claims.

Claims

1. A method for assembling a high-power energy storage device, characterized in that: The following steps are involved: Step 1: Energy storage device N i Discharge at 1C to the lower limit of use, then charge at a high current of 5C~10C constant current and constant voltage to the upper limit of charge, and then measure its internal resistance R i ; Step 2: After measuring the internal resistance, discharge the battery to the lower limit with a high current of more than 10C and record the discharge capacity C i , the voltage at the end of discharge is V i-0 , after the end of the 5s rebound voltage V i-5 ; Step 3: Non-dimensionalize the internal resistance, discharge capacity and rebound voltage, as follows: Among them, {R i } max , {R i } min Respectively represent the internal resistance of the energy storage device R i The maximum and minimum values ​​of i } max 、{C i } min Respectively represent the discharge capacity of the energy storage device C i The maximum and minimum values ​​of {V i-5 } max , {V i-5 } min Represents the rebound voltage V of the energy storage device i-5 The maximum and minimum values ​​of Step 4: After dimensionless processing, select energy storage devices that fall within a certain interval for grouping.

2. A high-power energy storage device assembly method according to claim 1, characterized in that: In step 1, the lower limit of use is 2.5V, and the upper limit of charging is 4.3V.

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