Method for evaluating on-orbit performance degradation of lithium ion storage battery pack for low-orbit spacecraft

Abstract

The method for evaluating the on-orbit performance degradation of the lithium ion storage battery pack for the low-orbit spacecraft comprises the following steps: acquiring a specific discharge initial voltage V0 and a specific discharge current I0 of the lithium ion storage battery pack under an on-orbit constant working condition; obtaining the final discharge voltage VE0 when the lithium ion storage battery pack is discharged to the specific discharge capacity C0; after the lithium ion storage battery pack flies in orbit for a specific time T, a discharge initial voltage V1 and a specific discharge current I1 are obtained; obtaining a final discharge voltage VE1 when the lithium ion storage battery pack is discharged to a specific discharge capacity C1; calculating the final discharge voltage value difference VE = VE0-VE1 after the lithium ion storage battery pack flies in orbit for a specific time; calculating the discharge final voltage attenuation value delta VE = VE / T of the lithium ion storage battery pack in each month of in-orbit flight; if delta VE is larger than or equal to the range threshold value, it is judged that the on-orbit performance of the lithium ion storage battery pack is not obviously attenuated; if delta VE is smaller than the range threshold value, it is judged that the on-orbit performance is attenuated.

Description

Technical Field

[0001] The present invention relates to the field of lithium-ion batteries for shallow-depth discharge in low-orbit satellites, and in particular to a method for evaluating on-orbit performance attenuation of lithium-ion battery packs for low-orbit spacecraft. Background Art

[0002] Lithium-ion batteries are widely used in aerospace, electric vehicles, new energy and other fields due to their excellent performance in parameters such as energy density and cycle life. During the continuous charging and discharging process of lithium-ion battery packs, the irreversible chemical reactions occurring inside them will cause the internal resistance of the battery cells to increase, the capacity to decrease, and the discharge voltage platform to decrease, causing the performance of the cells to degrade. In actual orbit, the cycle life of lithium-ion battery packs is mostly restricted by the final discharge voltage of the lithium-ion battery packs. As the number of cycles of lithium-ion battery packs on orbit increases, the performance of lithium-ion batteries decays, which is mainly manifested in the decrease of the final discharge voltage of the lithium-ion battery packs, further affecting the use of lithium-ion battery packs on orbit. The life of a battery pack is usually restricted by the final discharge voltage of the battery pack. Therefore, the decay of the final discharge voltage of the battery pack has an important impact on the performance of the battery pack and can effectively evaluate the performance decay of lithium-ion battery packs on orbit.

[0003] At present, the life prediction of lithium-ion battery packs for on-orbit space is mostly based on the analysis of test data from the ground testing phase and fitting prediction, which makes it difficult to truly reflect the cycle life and performance degradation of lithium-ion battery packs in the on-orbit space environment.

[0004] Therefore, a method is needed to accurately evaluate the actual cycle life and voltage attenuation on orbit and compare it with the consistency of ground tests. This can effectively reflect whether there is any abnormality in the performance attenuation of the battery pack on orbit, and further verify the accuracy of the ground simulation test, which will help to accurately evaluate the on-orbit life prediction of lithium-ion battery packs. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for evaluating the on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, which can accurately characterize the performance degradation of the on-orbit battery pack and effectively predict the on-orbit life of the battery pack by comparing it with the ground life test results.

[0006] In order to achieve the above-mentioned object, the present invention provides a method for evaluating the on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft, comprising: S1, obtaining a specific discharge starting voltage V0 of the lithium-ion battery pack under normal on-orbit operating conditions; S2, obtaining a specific discharge current I0 of the lithium-ion battery pack under normal on-orbit operating conditions; S3, obtaining a final discharge voltage V when the lithium-ion battery pack is discharged to a specific discharge capacity C0 under normal on-orbit operating conditions. E0; S4, after the lithium-ion battery pack has been in orbit for a specific time T, obtain the discharge starting voltage V1 of the lithium-ion battery pack under normal operating conditions on orbit; S5, obtain the specific discharge current I1 of the lithium-ion battery pack under normal operating conditions on orbit; S6, obtain the discharge final voltage V when the lithium-ion battery pack is discharged to a specific discharge capacity C1 under normal operating conditions on orbit E1 ; S7, calculate the discharge voltage difference △V of the lithium-ion battery pack after a specific time of flight in orbit E =V E0 -V E1 ; S8, calculate the monthly discharge voltage decay value δV of the lithium-ion battery pack during on-orbit flight E =△V E / T; S9, if δV E ≥ range threshold, it is determined that the on-orbit performance of the lithium-ion battery pack has not been significantly degraded; if δV E If the value is less than the range threshold, it is determined that the on-orbit performance of the lithium-ion battery pack has degraded.

[0007] In the above-mentioned method for evaluating the on-orbit performance attenuation of a lithium-ion battery pack for a low-orbit spacecraft, the on-orbit normal operating condition refers to the periodically repeated operating condition of the lithium-ion battery pack on orbit.

[0008] In the above-mentioned method for evaluating on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, the specific discharge starting voltage V0 in step 1) is 3.8×nV to 4.1×nV, where n is the number of battery packs connected in series.

[0009] In the above-mentioned method for evaluating on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, the specific discharge current I0 in step 2) is 0.1C to 1C.

[0010] The above-mentioned method for evaluating the on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, wherein the specific discharge capacity C0 in step 3) is 5% DOD to 40% DOD; the specific discharge final voltage V E0 3.0×nV~4.1×nV, where n is the number of battery packs connected in series.

[0011] In the above-mentioned method for evaluating on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, in step 4), the specific on-orbit flight time T is ≥ 3 months, in months; and the difference between the discharge starting voltage V1 and the specific discharge starting voltage V0 in step S1 cannot be greater than 0.2×nV, where n is the number of battery packs connected in series.

[0012] In the above-mentioned method for evaluating on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, in step 5), the difference between the specific discharge current I1 and the specific discharge current I0 in step S2 is ≤0.05C.

[0013] The above-mentioned method for evaluating the on-orbit performance degradation of lithium-ion batteries for low-orbit spacecraft, wherein, in step 6), the difference between the specific discharge capacity C1 and the specific discharge capacity C0 in step S3 is ≤5% SOC; the specific discharge terminal voltage V E1 3.0×n V to 4.1×n V, where n is the number of battery packs connected in series.

[0014] In the above-mentioned method for evaluating on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, in step 9), the range threshold is 3mV×n.

[0015] Compared with the prior art, the beneficial technical effects of the present invention are:

[0016] The present invention can accurately characterize the performance degradation of an on-orbit lithium-ion battery pack and, by comparing it with the life test results on the ground, effectively predict the on-orbit life of the battery pack. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The on-orbit performance degradation evaluation method of a lithium-ion battery pack for a low-orbit spacecraft of the present invention is provided by the following embodiments and accompanying drawings.

[0018] Figure 1 This is a flow chart of the on-orbit performance degradation assessment method for lithium-ion battery packs for low-orbit spacecraft of the present invention.

[0019] Figure 2 This is the voltage curve of a certain type of lithium-ion battery pack on track.

[0020] Figure 3 This is a curve of discharge voltage change of the same model of lithium-ion battery pack after on-orbit performance degradation.

[0021] Figure 4 This is a ground life test curve of lithium-ion battery cells of the same model. DETAILED DESCRIPTION

[0022] The following will be combined Figures 1 to 4 The method for evaluating the on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft of the present invention is further described in detail.

[0023] Figure 1 Shown is a flow chart of the on-orbit performance degradation evaluation method of a lithium-ion battery pack for a low-orbit spacecraft according to the present invention.

[0024] See also Figure 1 The method for evaluating the on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft of the present invention comprises:

[0025] S1. Obtaining a specific discharge starting voltage V0 of the lithium-ion battery pack under normal operating conditions;

[0026] The on-orbit normal operating condition refers to the periodic repetitive operating condition of the lithium-ion battery pack on-orbit;

[0027] The specific discharge starting voltage V0 is (3.8×n)V to (4.1×n)V, where n is the number of battery packs connected in series;

[0028] S2. Obtaining a specific discharge current I0 of the lithium-ion battery pack under normal operating conditions;

[0029] The specific discharge current I0 is 0.1C to 1C;

[0030] S3. Obtain the final discharge voltage V when the lithium-ion battery pack is discharged to a specific discharge capacity C0 under normal operating conditions. E0 ;

[0031] The specific discharge capacity C0 is 5% DOD to 40% DOD;

[0032] The specific discharge final voltage V E0 (3.0×n)V~(4.1×n)V;

[0033] S4. After the lithium-ion battery pack has been in orbit for a specific time T, obtaining a discharge starting voltage V1 of the lithium-ion battery pack under normal operating conditions on orbit;

[0034] The specific on-orbit flight time T is ≥ 3 months, in months;

[0035] The difference between the discharge starting voltage V1 and the specific discharge starting voltage V0 in step S1 cannot be greater than (0.2×n)V;

[0036] S5. Obtaining a specific discharge current I1 of the lithium-ion battery pack under normal operating conditions;

[0037] The difference between the specific discharge current I1 and the specific discharge current I0 in step S2 is ≤0.05C;

[0038] S6. Obtain the final discharge voltage V when the lithium-ion battery pack is discharged to a specific discharge capacity C1 under normal operating conditions. E1 ;

[0039] The difference between the specific discharge capacity C1 and the specific discharge capacity C0 in step S3 is ≤ 5% SOC;

[0040] The specific discharge final voltage V E1 (3.0×n)V~(4.1×n)V;

[0041] S7. Calculate the final discharge voltage difference △V of the lithium-ion battery pack after a specific time of in-orbit flight. E =VE0 -V E1 ;

[0042] S8. Calculate the monthly discharge voltage decay value δV of the lithium-ion battery pack during on-orbit flight. E =△V E / T;

[0043] S9, if δV E ≥ range threshold, it is determined that the on-orbit performance of the lithium-ion battery pack has not been significantly degraded; if δV E < the range threshold, it is determined that the on-orbit performance of the lithium-ion battery pack has degraded;

[0044] The range threshold is 3mV×n;

[0045] Discharge final voltage attenuation value δV E The more the range threshold is exceeded, the more obvious the on-orbit performance degradation of the lithium-ion battery pack.

[0046] Example:

[0047] The on-orbit performance degradation assessment method of a lithium-ion battery pack for a low-orbit spacecraft of this embodiment includes:

[0048] 1) Model I lithium-ion battery pack (150Ah lithium-ion battery pack, composed of 9 in series), with the discharge starting voltage V0 of the lithium-ion battery pack operating at normal power consumption being selected as 36.147V;

[0049] 2) Select the on-track discharge current of the lithium-ion battery pack at this time, I0 = 56.6A;

[0050] That is, the discharge current I0 of the lithium-ion battery pack when it works at normal power consumption is selected = 56.6A;

[0051] 3) Obtain the final discharge voltage V when the lithium-ion battery pack discharge capacity C0 = 19.34Ah E0 =34.702V;

[0052] 4) The discharge starting voltage V1 of the lithium-ion battery pack after T=12 months of on-orbit operation at normal on-orbit power consumption is 36.147V;

[0053] 5) Select the on-track discharge current I1 of the lithium-ion battery pack at this time = 59.2A;

[0054] That is, after the lithium-ion battery pack has been in orbit for 12 months, the discharge current I1=59.2A when working at the normal power consumption on orbit;

[0055] 6) Obtain the final discharge voltage V when the lithium-ion battery pack discharge capacity C1 = 19.49Ah E1 =34.628V;

[0056] 7) Calculate the difference in discharge voltage △V after the lithium-ion battery pack has been in orbit for 12 months E =V E0 -V E1 =34.702V-34.628V=0.074V=74mV;

[0057] 8) Calculate the monthly discharge voltage decay value δV of the lithium-ion battery pack during on-orbit flight E =△V E / T=74mV / 12=6.17mV.

[0058] This method is used to measure the attenuation value δV of lithium-ion battery pack of model I E The calculation results are shown in Table 1. From Table 1, we can see that the δV of the 9-series lithium-ion battery pack after one year of on-orbit operation is E It is 6.17mV, which is much smaller than the range threshold of 3mV×9=27mV, indicating that the performance of the lithium-ion battery pack has not degraded on orbit.

[0059] Table 1 Model I lithium ion battery pack attenuation value δV using this method E Calculation results

[0060]

[0061] This method is used to measure the attenuation value δV of the lithium-ion battery pack of type II (composed of 9 in series). E The calculation results are shown in Table 2. From Table 2, we can see that the δV of the model II 9 series lithium-ion battery pack after 3 years of on-orbit operation is E It is 38.72mV, which is greater than the range threshold of 3mV×9=27mV, indicating that the on-orbit performance of the lithium-ion battery pack has degraded to a certain extent.

[0062] Table 2: Attenuation value δV of lithium-ion battery pack of model II using this method E Calculation results

[0063]

[0064] Figure 2 The figure shows the voltage curve of a certain type of lithium-ion battery pack on track. Figure 2 It can be seen from the figure that the lithium-ion battery pack has not degraded after one year in orbit and has good on-orbit performance.

[0065] Figure 3 The figure shows the discharge voltage change curve of the same type of lithium-ion battery pack after on-orbit performance degradation. Figure 3It can be seen from the figure that after three years in orbit, the final discharge voltage of the lithium-ion battery pack has dropped significantly, the battery pack has operated abnormally in orbit, and its in-orbit performance has degraded to a certain extent.

[0066] Figure 4 The graph shows the ground life test curve of lithium-ion battery cells of the same model. Figure 4 The normal attenuation of the lithium-ion battery cell in the ground simulation test under the same working conditions can be seen.

[0067] The test results show that by calculating the battery pack discharge voltage difference δV E , which can accurately characterize the performance degradation of the on-orbit battery pack and effectively predict the on-orbit life of the battery pack by comparing it with the ground life test results.

[0068] The present invention provides a method for evaluating the on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft. By characterizing the change in the discharge final voltage of the on-orbit lithium-ion battery pack after a specific period of on-orbit operation, the method can accurately characterize the performance degradation of the on-orbit battery pack and effectively predict the on-orbit life of the battery pack by comparing it with the ground life test results.

[0069] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solutions of the present invention using the technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for evaluating the on-orbit performance degradation of lithium-ion battery packs for low-orbit spacecraft, characterized in that: include: S1. Obtaining a specific discharge starting voltage V0 of the lithium-ion battery pack under normal operating conditions; S2. Obtaining a specific discharge current I0 of the lithium-ion battery pack under normal operating conditions; S3. Obtain the final discharge voltage V when the lithium-ion battery pack is discharged to a specific discharge capacity C0 under normal operating conditions. E0 ; S4. After the lithium-ion battery pack has been in orbit for a specific time T, obtaining a discharge starting voltage V1 of the lithium-ion battery pack under normal operating conditions on orbit; S5. Obtaining a specific discharge current I1 of the lithium-ion battery pack under normal operating conditions; S6. Obtain the final discharge voltage V when the lithium-ion battery pack is discharged to a specific discharge capacity C1 under normal operating conditions. E1 ; S7. Calculate the final discharge voltage difference △V of the lithium-ion battery pack after a specific time of in-orbit flight. E =V E0 -V E1 ; S8. Calculate the monthly discharge voltage decay value δV of the lithium-ion battery pack during on-orbit flight. E =△V E / T; S9, if δV E ≥ range threshold, it is determined that the on-orbit performance of the lithium-ion battery pack has not been significantly degraded; if δV E If the value is less than the range threshold, it is determined that the on-orbit performance of the lithium-ion battery pack has degraded.

2. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: The on-orbit normal operating condition refers to the periodically repeated operating condition of the lithium-ion battery pack on-orbit.

3. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: The specific discharge starting voltage V0 in step 1) is 3.8×nV to 4.1×nV, where n is the number of battery packs connected in series.

4. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: The specific discharge current I0 in step 2) is 0.1C to 1C.

5. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: In step 3), the specific discharge capacity C0 is 5% DOD to 40% DOD; the specific discharge final voltage V E0 3.0×nV~4.1×nV, where n is the number of battery packs connected in series.

6. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: In step 4), the specific on-orbit flight time T is ≥ 3 months, in months; the difference between the discharge starting voltage V1 and the specific discharge starting voltage V0 in step S1 cannot be greater than 0.2×nV, where n is the number of battery packs connected in series.

7. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: In step 5), the difference between the specific discharge current I1 and the specific discharge current I0 in step S2 is ≤0.05C.

8. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: In step 6), the difference between the specific discharge capacity C1 and the specific discharge capacity C0 in step S3 is ≤5% SOC; the specific discharge final voltage V E1 3.0×n V to 4.1×n V, where n is the number of battery packs connected in series.

9. The method for evaluating on-orbit performance degradation of a lithium-ion battery pack for a low-orbit spacecraft according to claim 1, wherein: In step 9), the range threshold is 3mV×n.

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