Method and device for prolonging service life of single battery and vehicle

Abstract

The invention relates to the technical field of batteries, in particular to a method and device for prolonging the service life of a single battery and a vehicle, and the method comprises the following steps: setting the relation between the capacity CapVmax of the single battery under the maximum upper limit voltage Vmax and the capacity CapV0 of the single battery under the initial upper limit voltage V0 as follows: determining the health state of the single battery, and gradually increasing the upper limit cutoff voltage of the battery monomer according to the health state of the battery monomer. According to the invention, the cost can be controlled within a reasonable range while the cycle life of the battery is remarkably prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a method, a device and a vehicle for extending the life of a battery cell. Background Art

[0002] With the rapid development of the electronics and electric vehicle markets, end users have placed higher demands on the cycle life and performance stability of lithium-ion batteries. However, existing lithium-ion batteries generally suffer from capacity decay in practical applications, resulting in a reduced user experience and market complaints. To improve battery life, existing technologies in the industry are mainly divided into the following two categories:

[0003] 1. Optimization of battery cell chemistry

[0004] Using a cathode with greater structural stability, or a cathode material with fewer surface defects and fewer side reactions, can slow the initial capacity decay of the battery. While this can delay lifetime decay, it cannot completely prevent capacity loss. Furthermore, the use of high-cost materials significantly increases battery manufacturing costs, making large-scale promotion difficult in cost-sensitive markets.

[0005] 2. Use Strategy Optimization

[0006] Shallow charge and discharge strategy: By limiting the depth of battery charge and discharge (such as using only 30%-70% of the battery capacity), the loss of active materials can be reduced and the cycle life can be extended. For example, by designing the voltage difference of a composite positive electrode material (such as a mixture of lithium cobalt oxide and lithium iron phosphate), the battery can be cycled in a shallow charge and discharge range to reduce the capacity attenuation perceived by the user. This method requires a customized material system and is only applicable to specific application scenarios (such as low-power devices). It cannot cover areas with high energy density requirements such as electric vehicles; at the same time, insufficient battery capacity utilization leads to power waste (such as users can only use 70% of the power), which is less economical.

[0007] Secondary injection or repair technology: Replenishing electrolyte or repairing the electrode interface after battery degradation can partially restore capacity, but it is difficult to implement (battery disassembly is required), the cost is high, and the repair effect decreases significantly with the number of cycles.

[0008] However, the above approaches present challenges: while chemical system optimization can improve battery life, it's prohibitively expensive; while usage strategy optimization, while less expensive, is limited in scope and results in significant power waste. The conflict between user demand for battery life stability and insufficient battery capacity utilization remains unresolved.

[0009] Therefore, it is necessary to develop a new method, device and vehicle for extending the life of battery cells. Summary of the Invention

[0010] The object of the present invention is to provide a method, device and vehicle for extending the life of a battery cell, which can significantly extend the cycle life of the battery while keeping the cost within a reasonable range.

[0011] In a first aspect, a method for extending the life of a battery cell according to the present invention comprises the following steps:

[0012] The capacity Cap of the battery cell at the maximum upper voltage Vmax Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to:

[0013] Determine the health status of the battery cells and gradually increase the upper limit cut-off voltage of the battery cells according to the health status of the battery cells.

[0014] Preferably, the capacity Cap of the battery cell at the maximum upper voltage Vmax is Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to: This range not only compensates for capacity loss but also avoids cost waste due to excessive redundant capacity, achieving a win-win situation of extended battery life and economy, and adapting to the needs of mainstream application scenarios.

[0015] Preferably, the relationship between the maximum upper limit voltage Vmax and the initial upper limit voltage V0 satisfies: Vmax-V0≤1000mv; wherein, Vmax≥3650mv. The upper limit voltage of the current mainstream battery cells is basically greater than or equal to 3650mv, so Vmax≥3650mv is set. Different Vmax and V0 will affect the characteristic parameters of the software (such as internal resistance, SOC calculation, power closed-loop strategy, etc.). At the same time, the voltage difference is also consistent with the capacity difference logic. A large amount of voltage redundancy brings a large amount of capacity redundancy. While ensuring the performance compensation effect, it reduces the initial cost of the battery, so it is necessary to set Vmax-V0≤1000mv.

[0016] Preferably, the relationship between the maximum upper limit voltage Vmax and the initial upper limit voltage V0 satisfies: Vmax-V0≤200mv, thereby further ensuring the performance compensation effect while reducing the initial cost of the battery.

[0017] Preferably, the energy E of the battery cell at the maximum upper voltage Vmax is Vmax The capacity E at the initial upper limit voltage V0 V0 The relationship is set to: This ratio reflects the average voltage and can be used to indirectly evaluate the slip of the voltage curve within the entire voltage application range. If the slip deviation is large (currently controlled at 5%-10%), it will affect the SOC calculation. Therefore, setting the ratio to fluctuate within 10% will have little impact on the parameters.

[0018] Preferably, the amplitude ΔV of each battery cell's upper cut-off voltage increase satisfies the following requirements: ΔV ≥ 5mv. By setting ΔV ≥ 5mV, it is ensured that the voltage increase amplitude can still achieve the expected effect under the BMS sampling error (± 2mV). In extreme sampling conditions, it is necessary to ensure that the actual increase amplitude is greater than 4mV to trigger effective compensation. Therefore, setting ΔV ≥ 5mV can cover the error range, avoid voltage adjustment failure due to sampling fluctuations, and ensure the reliability of the dynamic voltage strategy and the accuracy of capacity compensation.

[0019] Preferably, the capacity of the battery cell deteriorates during use. loss Increased capacity Cap due to increased upper limit voltage at the corresponding moment up Relationship Satisfaction: Cap loss -Cap up ≥0. By constraining the capacity after voltage opening to ≤ initial capacity, dual protection of user experience and software reliability is achieved. On the one hand, based on the acceptable range of the user's initial capacity, the capacity after compensation does not exceed the limit to ensure that user needs are always met (such as consistency in battery life perception); on the other hand, if the capacity after compensation exceeds the initial value (SOH>100%), it will lead to SOC calculation deviation (such as overestimation of remaining power) and failure of the power closed-loop strategy (such as overcharging risk). This limitation balances capacity compensation and algorithm stability, while avoiding software anomalies to extend battery life and ensure safe and efficient operation of the system.

[0020] Preferably, the degraded capacity of the battery cell when the voltage is first increased should meet the following requirements: When the battery capacity decays to 90% of its initial value (for example, a vehicle's range drops from 600km to 540km, a noticeable decrease in range for the user), a voltage increase is triggered to ensure timely compensation intervention. This threshold effectively reduces the user's perception of range decay (for example, maintaining range above 580km), avoiding a degraded user experience due to delayed compensation. It also accounts for the voltage adjustment strategy's sensitivity to capacity decay, achieving a dynamic balance between range perception and system control.

[0021] In a second aspect, the present invention provides a device for extending the life of a battery cell, comprising:

[0022] Configuration module, used to set the capacity Cap of the battery cell at the maximum upper voltage Vmax Vmax Capacity Cap at the initial upper limit voltage V0 V0The relationship is set to:

[0023] The life extension module is used to determine the health status of the battery cell and gradually increase the upper limit cut-off voltage of the battery cell according to the health status of the battery cell.

[0024] In a third aspect, a vehicle according to the present invention includes a power battery having a plurality of battery cells, and the power battery is connected to a device for extending the life of the battery cells as described in an embodiment of the present application.

[0025] Beneficial effects of the present invention: The present invention gradually increases the upper limit operating voltage during battery attenuation to compensate for capacity loss. While significantly extending the battery cycle life, it does not require expensive modifications to the battery cell chemical system, keeping costs within a reasonable range and meeting the demand for cost-effective and long-life batteries in the fields of electronic products and electric vehicles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a flow chart of the method for extending the life of a battery cell in an embodiment of the present application;

[0027] Figure 2 It is the upper limit voltage change curve of the NCM battery cell cycle process;

[0028] Figure 3 This is the upper limit voltage change curve of the LFP battery cell cycle process;

[0029] Figure 4 This is a principle block diagram of the device for extending the life of a battery cell described in an embodiment of the present application. DETAILED DESCRIPTION

[0030] The following will describe the embodiments of the present invention with reference to the accompanying drawings and preferred embodiments. Those skilled in the art will be able to understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for the purpose of illustrating the present invention and are not intended to limit the scope of protection of the present invention.

[0031] like Figure 1 As shown, in an embodiment of the present application, a method for extending the life of a battery cell includes the following steps:

[0032] The capacity Cap of the battery cell at the maximum upper voltage Vmax Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set up as: Determine the health status of the battery cells and gradually increase the upper limit cut-off voltage of the battery cells according to the health status of the battery cells.

[0033] Battery cells have different capacity performances in different [lower application cut-off voltage, upper application cut-off voltage] ranges, and as the upper application cut-off voltage increases, the capacity of the battery cells will also increase. The current mainstream battery warranty standards usually require a health state (SOH) ≥ 75% (some high-end warranties are 10 years or 300,000 kilometers under SOH ≥ 70%), that is, the maximum allowable capacity attenuation is 25%. By increasing the voltage to compensate for capacity attenuation, the maximum "capacity replenishment" amount must match the warranty attenuation upper limit, so the Cap Vmax Relative to Cap V0 The upper limit for capacity increase is set at 25% to ensure that the capacity replenishment effect does not exceed the warranty-permitted degradation range. Furthermore, excessive capacity redundancy will also increase the cost of the battery cells. Assuming a cell capacity degradation of 0.25%, based on the vehicle's nominal range of 600 kilometers, this corresponds to a range reduction of only 1.5 kilometers. The difference between the displayed range and the actual experience is almost the same, so the lower limit is set at 0.25%.

[0034] The calculation was performed using an LFP (lithium iron phosphate) battery with a capacity of 85Ah and a 50% SOC at room temperature. When the upper cut-off voltage was opened from 3.6V to 3.65V, which was a 50mv increase, the recharge power increased by 20% (corresponding to 300w here). According to the vehicle's WLTC operating conditions (Worldwide Harmonized Light Vehicle Test Cycle), the recharge capacity accounts for 25%. Based on a 600km range model, the recharge capacity has a range of 150km, the power increased by 20%, the recharge capacity increased by 5%, and the range increased by 7.5km.

[0035] In a possible embodiment, the capacity Cap of the battery cell at the maximum upper voltage Vmax is Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to: This range not only compensates for capacity loss but also avoids cost waste due to excessive redundant capacity, achieving a win-win situation of extended battery life and economy, and adapting to the needs of mainstream application scenarios.

[0036] In one possible embodiment, the relationship between the maximum upper limit voltage Vmax and the initial upper limit voltage V0 satisfies: Vmax-V0≤1000mv; wherein, Vmax≥3650mv. The upper limit voltage of current mainstream battery cells is basically greater than or equal to 3650mv, so Vmax≥3650mv is set. Different Vmax and V0 will affect the characteristic parameters of the software (such as internal resistance, SOC calculation, power closed-loop strategy, etc.). At the same time, the voltage difference is also consistent with the capacity difference logic. A large amount of voltage redundancy brings a large amount of capacity redundancy. While ensuring the performance compensation effect, it is necessary to reduce the initial cost of the battery. Therefore, it is necessary to set Vmax-V0≤1000mv.

[0037] In a possible embodiment, the relationship between the maximum upper limit voltage Vmax and the initial upper limit voltage V0 satisfies: Vmax-V0≤200mv, thereby further ensuring the performance compensation effect while reducing the initial cost of the battery.

[0038] In a possible embodiment, the energy E of the battery cell at the maximum upper voltage Vmax is Vmax The capacity E at the initial upper limit voltage V0 V0 The relationship is set to: This ratio reflects the average voltage and can be used to indirectly evaluate the slip of the voltage curve within the entire voltage application range. If the slip deviation is large (currently controlled at 5%-10%), it will affect the SOC calculation. Therefore, setting the ratio to fluctuate within 10% will have little impact on the parameters.

[0039] In one possible embodiment, the amplitude ΔV of each battery cell's upper cut-off voltage increase satisfies: ΔV ≥ 5mv. By setting ΔV ≥ 5mV, it is ensured that the voltage increase amplitude can still achieve the expected effect under the BMS sampling error (± 2mV). In extreme sampling conditions, it is necessary to ensure that the actual increase amplitude is greater than 4mV to trigger effective compensation. Therefore, setting ΔV ≥ 5mV can cover the error range, avoid voltage adjustment failure due to sampling fluctuations, and ensure the reliability of the dynamic voltage strategy and the accuracy of capacity compensation.

[0040] In a possible embodiment, the capacity Cap of the battery cell degrades during use. loss Increased capacity Cap due to increased upper limit voltage at the corresponding moment up Relationship Satisfaction: Cap loss -Cap up≥0. By constraining the capacity after voltage opening to ≤ initial capacity, dual protection of user experience and software reliability is achieved. On the one hand, based on the acceptable range of the user's initial capacity, the capacity after compensation does not exceed the limit to ensure that user needs are always met (such as consistency in battery life perception); on the other hand, if the capacity after compensation exceeds the initial value (ie SOH>100%), it will lead to SOC calculation deviation (such as overestimation of remaining power) and failure of the power closed-loop strategy (such as overcharging risk). This limitation balances capacity compensation and algorithm stability, while avoiding software anomalies to extend battery life and ensure safe and efficient operation of the system.

[0041] In a possible embodiment, the degraded capacity of a battery cell when the voltage is first increased should meet the following requirements: When the battery capacity decays to 90% of its initial value (for example, a vehicle's range drops from 600km to 540km, a noticeable decrease in range for the user), a voltage increase is triggered to ensure timely compensation intervention. This threshold effectively reduces the user's perception of range decay (for example, maintaining range above 580km), avoiding a degraded user experience due to delayed compensation. It also accounts for the voltage adjustment strategy's sensitivity to capacity decay, achieving a dynamic balance between range perception and system control.

[0042] Comparative Example 1 (NCM battery: nickel cobalt manganese oxide battery)

[0043] Adopting the NCM system, the rated capacity of the battery cell is 135Ah (1C) in the voltage range of 3.10V to 4.30V. At room temperature (25℃), the voltage application range is maintained throughout: the upper limit voltage is 4.3V and the lower limit voltage is 3.10V.

[0044] The cycle test process is as follows:

[0045] S1: In the charging stage, the battery cell is first charged with a constant current of 1C. When the voltage of the battery cell reaches the upper cut-off voltage, the charging mode is switched to constant voltage charging.

[0046] S2: After charging is completed, let the battery cell stand for 10 minutes.

[0047] S3: During the discharge phase, the battery cells are discharged at a constant current of 0.33C. Discharge ends when the battery cell voltage drops to the set lower cutoff voltage (3.1V). The capacity released during the first discharge is recorded and set as 100%. This capacity is used as the basis for calculating the capacity retention rate in subsequent tests.

[0048] S4: After the discharge is completed, the battery cell is left to stand for 10 minutes.

[0049] S5: Cycle S1-S4 for a total of 2000 cls or capacity retention rate ≤ 70%.

[0050] Comparative Example 2 (LFP battery: lithium iron phosphate battery)

[0051] Using the LFP system, the rated capacity of the battery cell is 85Ah (1C) in the voltage range of 2.5V to 3.60V. At room temperature (25°C), the voltage application range is maintained throughout: the upper limit voltage is 3.60V and the lower limit voltage is 2.50V.

[0052] The cycle test process is as follows:

[0053] S1: In the charging stage, the battery cell is first charged with a constant current of 1C. When the voltage of the battery cell reaches the upper cut-off voltage, the charging mode is switched to constant voltage charging.

[0054] S2: After charging is completed, let the battery cell stand for 10 minutes.

[0055] S3: During the discharge phase, the battery cells are discharged at a constant current of 0.33C. Discharge ends when the cell voltage drops to the set lower cutoff voltage (2.5V). The capacity released during the first discharge is recorded and set as 100%. This capacity is used as the basis for calculating the capacity retention rate in subsequent tests.

[0056] S4: After the discharge is completed, the battery cell is left to stand for 10 minutes.

[0057] S5: Cycle S1-S4 for a total of 2000 cls or capacity retention rate ≤ 70%.

[0058] Example 1 (NCM)

[0059] Using the same battery cells as in Comparative Example 1, the voltage application range at room temperature (25°C) is maintained as follows: the initial upper limit voltage cutoff is 4.3V, and the voltage upper limit increases by 0.005V every 200cls of the cycle until the voltage reaches 4.35V after 2000cls. The lower limit voltage is maintained at 3.10V throughout the entire process. Other test conditions remain the same as in Comparative Example 1.

[0060] Example 2 (NCM)

[0061] Using the same battery cells as in Comparative Example 1, the voltage application range at room temperature (25°C) is maintained as follows: the initial upper limit voltage cutoff is 4.3V, and the voltage upper limit increases by 0.01V every 200cls of the cycle until the voltage reaches 4.4V after 2000cls. The lower limit voltage is maintained at 3.10V throughout the entire process. Other test conditions remain the same as in Comparative Example 1.

[0062] Example 3 (LFP)

[0063] Using the same battery cells as in Comparative Example 2, the voltage application range at room temperature (25°C) is maintained as follows: the initial upper limit voltage cutoff is 3.6V, and the voltage upper limit increases by 0.01V every 200cls of the cycle until the voltage reaches 3.7V after 2000cls. The lower limit voltage is maintained at 2.5V throughout the entire process. Other test conditions remain the same as in Comparative Example 1.

[0064] Example 4 (LFP)

[0065] Using the same battery cells as in Comparative Example 2, the voltage application range at room temperature (25°C) is maintained as follows: the initial upper limit voltage cutoff is 3.6V, and the voltage upper limit increases by 0.02V every 200cls of the cycle until the voltage reaches 3.8V after 2000cls. The lower limit voltage is maintained at 2.5V throughout the entire process. Other test conditions remain the same as in Comparative Example 1.

[0066] like Figure 2 As shown in the figure, the change curve of the upper limit cut-off voltage during the cycle of the NCM battery cell can intuitively reflect the voltage performance of the voltage opening process through the change curve.

[0067] like Figure 3 As shown in the figure, the change curve of the upper limit cut-off voltage during the LFP battery cell cycle can intuitively reflect the voltage performance of the voltage opening process through the change curve.

[0068] The results are compared as follows:

[0069] Initial capacity / Ah 1000cls capacity 1000cls retention rate 2000cls capacity 2000cls retention rate Comparative Example 1 135 119.6 88.6％ 99.4 73.6％ Example 1 135 120.8 89.5％ 102.5 75.9％ Example 2 135 122.5 90.7％ 104.9 77.7％ Comparative Example 2 85 78.4 92.2％ 70.3 82.7％ Example 3 85 78.9 92.8％ 71 83.5％ Example 4 85 79.1 93.1％ 71.2 83.8％

[0070] Experimental summary: In the NCM and LFP systems, gradually increasing the upper limit voltage can improve the capacity retention rate.

[0071] In an embodiment of the present application, a device for extending the life of a battery cell includes a configuration module and a life extension module. The configuration module is used to set the capacity Cap of the battery cell at the maximum upper voltage Vmax to Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to: The life extension module is used to determine the health status of the battery cell and gradually increase the upper limit cut-off voltage of the battery cell according to the health status of the battery cell.

[0072] In an embodiment of the present application, a vehicle includes a power battery having multiple battery cells, each of which is connected to a device for extending the life of the battery cell as described in an embodiment of the present application. The vehicle may be, but is not limited to, a pure electric vehicle (PEV / BEV), a hybrid electric vehicle (HEV), a range extended electric vehicle (REEV), a plug-in hybrid electric vehicle (PHEV), a new energy vehicle, etc.

[0073] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for extending the life of a battery cell, characterized in that: The following steps are involved: The capacity Cap of the battery cell at the maximum upper voltage Vmax Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to: Determine the health status of the battery cells and gradually increase the upper cut-off voltage of the battery cells according to the health status of the battery cells.

2. The method for extending the life of a battery cell according to claim 1, characterized in that: The capacity Cap of the battery cell at the maximum upper voltage Vmax Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to:

3. The method for extending the life of a battery cell according to claim 1, wherein: The relationship between the maximum upper limit voltage Vmax and the initial upper limit voltage V0 satisfies: Vmax-V0≤1000mv; wherein, Vmax≥3650mv.

4. The method for extending the life of a battery cell according to claim 3, wherein: The relationship between the maximum upper limit voltage Vmax and the initial upper limit voltage V0 satisfies: Vmax-V0≤200mv.

5. The method for extending the life of a battery cell according to claim 1, wherein: The energy E of the battery cell at the maximum upper voltage Vmax Vmax The capacity E at the initial upper limit voltage V0 V0 The relationship is set to:

6. The method for extending the life of a battery cell according to claim 1, wherein: The amplitude ΔV of the upper cut-off voltage of the battery cell each time is increased satisfies: ΔV≥5mv.

7. The method for extending the life of a battery cell according to claim 1, wherein: The capacity of the battery cell deteriorates during use. loss Increased capacity Cap due to increased upper limit voltage at the corresponding moment up Relationship satisfaction: Cape loss -Cap up ≥0.

8. The method for extending the life of a battery cell according to claim 7, characterized in that: The degradation capacity of the battery cell when the voltage is first increased should meet the following requirements:

9. A device for extending the life of a battery cell, characterized in that: include: Configuration module, used to set the capacity Cap of the battery cell at the maximum upper voltage Vmax Vmax Capacity Cap at the initial upper limit voltage V0 V0 The relationship is set to: The life extension module is used to determine the health status of the battery cell and gradually increase the upper limit cut-off voltage of the battery cell according to the health status of the battery cell.

10. A vehicle comprising a power battery having a plurality of battery cells, characterized in that: The power battery is connected to the device for extending the life of a battery cell as claimed in claim 9.

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