Battery pack and electric equipment

Abstract

A battery pack includes: a first power supply unit including a first cathode tab including a first lithium transition metal oxide containing a nickel element, the molar ratio of the nickel element in the first lithium transition metal oxide being greater than a first content threshold; the second power supply unit comprises a second cathode pole piece and a second lithium transition metal oxide containing the nickel element, and the molar ratio of the nickel element in the second lithium transition metal oxide is smaller than or equal to the first content threshold value; the battery management system is configured to obtain the temperature and the charge-discharge rate of the battery pack; when the temperature is smaller than or equal to a first temperature threshold and the charge-discharge rate is smaller than or equal to a first rate threshold, the first power supply unit supplies energy, and the second power supply unit is in a dormant state; when the temperature is larger than the first temperature threshold value and / or the charge-discharge rate is larger than the first rate threshold value, the second power supply unit supplies energy, and the first power supply unit is in a dormant state.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a battery pack and an electrical device. Background Technology

[0002] As the country vigorously promotes new energy equipment, its market share is constantly increasing, and people's requirements for new energy equipment are also getting higher and higher. For example, the energy storage batteries in new energy equipment need to have higher energy density and longer service life.

[0003] Currently, the most commonly used energy storage batteries in new energy equipment are lithium-ion secondary batteries, which are composed of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, and other ternary batteries containing nickel, cobalt, and manganese. This type of battery can no longer simultaneously meet the demands for higher energy density and longer lifespan. Summary of the Invention

[0004] This application provides a battery pack and an electrical device that can improve the energy density of the battery pack and extend its service life.

[0005] In a first aspect, embodiments of this application provide a battery pack, comprising a first power supply unit, a second power supply unit, and a battery management system. The first power supply unit includes a first cathode electrode comprising a first lithium transition metal oxide containing nickel. Based on the total molar number of metal atoms other than Li atoms in the active material of the first cathode electrode, the molar percentage of nickel in the first lithium transition metal oxide is greater than a first content threshold. The second power supply unit includes a second cathode electrode comprising a second lithium transition metal oxide containing nickel. Based on the total molar number of metal atoms other than Li atoms in the active material of the second cathode electrode, the molar percentage of nickel in the second lithium transition metal oxide is less than or equal to the first content threshold. The battery management system is configured to: acquire the temperature and charge / discharge rate of the battery pack; in response to a temperature less than or equal to a first temperature threshold and a charge / discharge rate less than or equal to a first rate threshold, control the first power supply unit to supply power and control the second power supply unit to be in a dormant state; in response to a temperature greater than the first temperature threshold and / or a charge / discharge rate greater than the first rate threshold, control the second power supply unit to supply power and control the first power supply unit to be in a dormant state.

[0006] When the temperature is less than or equal to the first temperature threshold and the charge / discharge rate is less than or equal to the first rate threshold, it means that the current temperature and charge / discharge rate are low. Under these conditions, the first power supply unit is used for power supply, and the risk of abnormal situations such as gas generation, capacity loss, or cycle degradation in the first power supply unit is low, resulting in a longer service life for the first power supply unit. Secondly, due to the high nickel content of the first cathode electrode, the battery pack can have a high energy density. In addition, by controlling the second power supply unit to be in a dormant state, the second power supply unit stops supplying power and serves as a backup power supply unit. When the temperature is greater than the first temperature threshold, or the charge / discharge rate is greater than the first rate threshold, the second power supply unit can be used for power supply, thereby extending the service life of the battery pack.

[0007] In one or more embodiments, the first content threshold is 85%.

[0008] In one or more embodiments, the ratio of the capacity of the first power supply unit to the total capacity is 70%-85%, wherein the total capacity is the sum of the capacities of the first power supply unit and the second power supply unit.

[0009] Thus, the first power supply unit serves as the main power supply unit, and the second power supply unit serves as the auxiliary power supply unit, ensuring that the battery pack has a high energy density. The first power supply unit is responsible for daily operation and long driving range, providing the vast majority of the energy; the second power supply unit is responsible for power supply under specific conditions, such as when the first power supply unit is in sleep mode or disconnected.

[0010] In one or more embodiments, in response to a temperature greater than a first temperature threshold and / or a charge / discharge rate greater than a first rate threshold, controlling the second power supply unit to supply power and controlling the first power supply unit to be in a sleep state includes: in response to a temperature greater than the first temperature threshold and the current state of charge of the first power supply unit being less than or equal to a first state of charge threshold, controlling the first power supply unit to enter a sleep state.

[0011] If the temperature is greater than the first temperature threshold, the first power supply unit can also be controlled to enter a sleep state if its current state of charge is less than or equal to the first state of charge threshold. At this time, since the current state of charge of the first power supply unit is low, even if the temperature is too high, the risk of abnormal situations such as gas generation, capacity loss or cycle decay of the first power supply unit is low, which helps to extend the service life of the first power supply unit.

[0012] In one or more embodiments, the first state of charge threshold is 30%.

[0013] In one or more embodiments, in response to a temperature greater than a first temperature threshold and / or a charge / discharge rate greater than a first rate threshold, controlling the second power supply unit to supply power and controlling the first power supply unit to be in a sleep state includes: in response to a temperature greater than the first temperature threshold and the current state of charge of the first power supply unit being greater than a first state of charge threshold, controlling the first power supply unit to discharge; in response to the first power supply unit discharging until the state of charge of the first power supply unit is less than or equal to a second state of charge threshold, controlling the first power supply unit to enter a sleep state.

[0014] When the temperature exceeds a first temperature threshold and the current state of charge (SBC) of the first power supply unit is also greater than the first SBC threshold, directly controlling the first power supply unit to enter a dormant state carries a high risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation due to excessively high temperature. Therefore, this embodiment first controls the first power supply unit to discharge, reducing its SBC. Only when the SBC is reduced to less than or equal to a second SBC threshold is the first power supply unit controlled to enter a dormant state. At this point, because the current SBC is lower, the risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation is lower even if the temperature is too high, thus extending the service life of the first power supply unit.

[0015] In one or more embodiments, the second state of charge threshold is 0.

[0016] When the temperature exceeds the first temperature threshold, by reducing the state of charge of the first power supply unit to 0, the risk of abnormal situations such as gas generation, capacity loss or cycle decay caused by excessive temperature can be effectively reduced after the first power supply unit is controlled to enter a dormant state, thereby helping to extend the service life of the first power supply unit.

[0017] In one or more embodiments, the first temperature threshold is 45°C.

[0018] When the temperature exceeds 45°C, the first power supply unit is at high risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation, and these abnormal conditions may rapidly worsen. Therefore, by setting the first temperature threshold to 45°C and taking timely intervention measures, it is beneficial to effectively reduce the above risks and extend the service life of the battery pack.

[0019] In one or more embodiments, the first magnification threshold is 8C.

[0020] When the charge / discharge rate is greater than 8C, the first power supply unit is at high risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation, and these abnormal conditions may rapidly worsen. Therefore, by setting the first temperature threshold to 8C and taking timely intervention measures, it is beneficial to effectively reduce the above risks and extend the service life of the battery pack.

[0021] In one or more embodiments, the specific capacity of the first lithium transition metal oxide is 205-215 mAh / g, and / or the specific capacity of the second lithium transition metal oxide is 100-204 mAh / g.

[0022] Secondly, embodiments of this application provide an electrical device, including a load and a battery pack as described in the first aspect. Attached Figure Description

[0023] One or more embodiments are illustrated by way of example with reference to the accompanying drawings, which are not intended to limit the embodiments, and elements having the same reference numerals in the drawings are designated as similar elements.

[0024] Figure 1 This is a schematic diagram of the battery pack provided in the embodiments of this application. Figure 1 ; Figure 2 This is a schematic diagram of the battery pack provided in the embodiments of this application. Figure 2 ; Figure 3 This is a flowchart of the method executed by the battery management system provided in the embodiments of this application. Figure 1 ; Figure 4 This is a flowchart of the method executed by the battery management system provided in the embodiments of this application. Figure 2 . Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0026] It should be noted that when an element is described as "connected" to another element, it can be directly connected to the other element, or there can be one or more intermediate elements between them.

[0027] Furthermore, the technical features involved in the various embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0028] Please refer to Figure 1 , Figure 1 This is one structure of a battery pack provided in an embodiment of this application. For example... Figure 1 As shown, the battery pack 10 includes a first power supply unit 11, a second power supply unit 12, and a battery management system 13. Optionally or additionally, the ratio of the capacity of the first power supply unit 11 to the total capacity is 70%-85%, where the total capacity is the sum of the capacities of the first power supply unit 11 and the second power supply unit 12. Thus, the first power supply unit 11 serves as the main power supply unit, and the second power supply unit 12 serves as the auxiliary power supply unit to ensure that the battery pack 10 has a high energy density. Optionally or additionally, the first power supply unit 11 is responsible for daily operation and long-range driving, providing the majority of the energy; the second power supply unit 12 is responsible for power supply under specific conditions, such as when the first power supply unit 11 is in sleep mode or disconnected.

[0029] Understandable Figure 1 Taking a battery pack 10 comprising a first power supply unit 11 and a second power supply unit 12 as an example. Optionally or additionally, the battery pack 10 includes N first power supply units 11 and M second power supply units 12, where N and M are both positive integers greater than 0, and N and M can be the same or different. For example, as... Figure 2 As shown, N=M=2, meaning that the battery pack 10 includes two first power supply units 11 and two second power supply units 12.

[0030] The first power supply unit 11 includes a first cathode electrode 111, which is the positive electrode. The first cathode electrode 111 is made by coating a metal foil (usually aluminum foil) with a mixture of active materials, conductive agents, binders and the like.

[0031] The active material of the first cathode electrode 111 includes a first lithium transition metal oxide containing nickel. The first lithium transition metal oxide refers to an inorganic compound composed of lithium (Li), oxygen (O), and one or more transition metals (M), with the chemical formula LiNi. x Co y M 1-x-y O2 (x≥0.85, 0<y≤0.1), where M can be selected from Mn or Al, or it can be coated or doped.

[0032] Based on the total molar number of metal atoms other than Li atoms in the active material of the first cathode electrode 111, the molar percentage of nickel in the first lithium transition metal oxide is greater than a first content threshold. Here, the calculation basis is clearly defined as the mass of the active material in the first cathode electrode 111, not the mass of the entire electrode (including conductive carbon black, binder, current collector, etc.). Therefore, the molar percentage of nickel does not refer to the weight percentage of nickel in the entire cathode electrode, but rather the percentage of nickel atoms (Ni) relative to the total number of all transition metal atoms (such as Ni, Mn, Co, Al, etc.) in the active material. For example, in NCM811 (i.e., LiNi... 0.8 Co 0.1 Mn 0.1 In O2, the molar ratio of nickel, manganese, and cobalt is 8:1:1, so the molar percentage of nickel is 8 / (8+1+1)=80%; For example, LiNi 0.90 Co 0.05 Mn 0.05 In O2, the molar ratio of nickel, manganese, and cobalt is 9:0.5:0.5, so the molar percentage of nickel is 9 / (9+0.5+0.5)=90%. A molar percentage of nickel in the first lithium transition metal oxide greater than a first content threshold means that the nickel content in the first lithium transition metal oxide is high, thus enabling the first power supply unit 11 to have a high energy density. The first content threshold is a preset threshold that can be set based on actual application scenarios. For example, in a specific embodiment, the first content threshold is 85% to ensure that the first power supply unit 11 has a high energy density.

[0033] The second power supply unit 12 includes a second cathode electrode 121, which is made by coating a metal foil (usually aluminum foil) with a mixture of active materials, conductive agents, binders, etc.

[0034] The active material of the second cathode electrode 121 includes a second lithium transition metal oxide containing nickel. The second lithium transition metal oxide refers to an inorganic compound composed of lithium (Li), oxygen (O) and one or more transition metals (M), with the general formula generally being LiMO2. M can be selected from at least one of Ni, Co, Mn, Al, Cr, Fe, etc., such as lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium manganese oxide (LMO), lithium cobalt oxide (LCO), lithium iron phosphate (LFP), lithium iron manganese phosphate (LMFP), etc. It can also be coated or doped with elements.

[0035] Optionally or additionally, the second lithium transition metal oxide contains nickel. Based on the total molar number of metal atoms other than Li atoms in the active material of the second cathode electrode, the molar percentage of nickel in the second lithium transition metal oxide is less than or equal to a first content threshold. Specifically, it can be NCM811, NCM622, NCM523, NCM424, etc., which are well known to those skilled in the art. The calculation basis, based on the mass of the active material in the second cathode electrode 121, is the mass of the active material, not the mass of the entire electrode. Therefore, the molar percentage of nickel does not refer to the weight percentage of nickel in the entire cathode electrode, but rather the percentage of nickel atoms in the active material relative to the total number of transition metal atoms. A molar percentage of nickel in the second lithium transition metal oxide less than or equal to the first content threshold means that the nickel content in the second lithium transition metal oxide is low, thus resulting in better high-temperature stability of the second power supply unit 12.

[0036] Optionally or additionally, the specific capacity of the first lithium transition metal oxide is 205-215 mAh / g, and / or the specific capacity of the second lithium transition metal oxide is 100-204 mAh / g. Specific capacity refers to the electrical capacity provided by a unit mass of active material, expressed in mAh / g. A specific capacity of 205-215 mAh / g for the first lithium transition metal oxide indicates a high specific capacity. Optionally or additionally, the first lithium transition metal oxide may include high-nickel ternary materials (such as LiNi). 0.9 Co 0.05 Mn 0.05 O2, or other ternary materials with higher Ni content, or coating or elemental doping thereof). The specific capacity of the second lithium transition metal oxide is 100-204 mAh / g, which means that the specific capacity of the metal oxide is low. Optionally or additionally, the second lithium transition metal oxide includes lithium iron phosphate (LiFePO4, LFP), medium-nickel ternary materials (such as NCM523, NCM622, etc.), lithium manganese oxide (LiMn2O4, LMO), lithium cobalt oxide (LiCoO2, LCO), etc.

[0037] Please refer to the above as well. Figure 3 , Figure 3 A flowchart illustrating the method performed by the Battery Management System (BMS) 13 provided in this embodiment of the application. Figure 3 As shown, the battery management system 13 is configured to perform steps S310 to S330.

[0038] Step S310: Obtain the temperature and charge / discharge rate of the battery pack.

[0039] The battery management system 13 typically monitors the battery pack temperature using a thermistor (such as an NTC or PTC). The charge / discharge rate is a relative value, representing the ratio of current to battery capacity. Its calculation formula is: Charge / Discharge Rate C - rate = Current (A) / Rated Capacity (Ah). For example, a 50Ah battery currently discharging at 100A has a discharge rate of 100A / 50Ah = 2C. The battery management system 13 can calculate the current charge / discharge rate using the known rated battery capacity and the measured real-time current.

[0040] Step S320: In response to the temperature being less than or equal to a first temperature threshold and the charge / discharge rate being less than or equal to a first rate threshold, control the first power supply unit to supply power and control the second power supply unit to be in a sleep state.

[0041] Wherein, the first temperature threshold is a preset temperature threshold, and the first multiplier threshold is a preset multiplier threshold. Both can be set based on the actual application scenario, and this application embodiment does not impose specific restrictions on them.

[0042] Specifically, when the temperature is less than or equal to the first temperature threshold and the charge / discharge rate is less than or equal to the first rate threshold, it means that the current temperature and charge / discharge rate are low. Under such circumstances, the first power supply unit 11 is used to supply power, and the risk of abnormal situations such as gas generation, capacity loss, or cycle decay of the first power supply unit 11 is low, and the first power supply unit 11 has a long service life. Secondly, since the nickel content of the first cathode electrode is high, the battery pack 10 can have a high energy density. In addition, if the second power supply unit 12 is controlled to be in a dormant state, the second power supply unit 12 will stop supplying power and serve as a backup power supply unit. When the temperature is greater than the first temperature threshold or the charge / discharge rate is greater than the first rate threshold, the second power supply unit 12 can be used to supply power, thereby extending the service life of the battery pack. Among these phenomena, gas production manifests as battery bulging and increased internal pressure. This is caused by the oxidative decomposition of the electrolyte on the highly active positive electrode surface, producing gases such as CO2 and CO; the reaction of residual lithium impurities on the material surface with the electrolyte; and the destruction and regeneration of the SEI film on the negative electrode at high temperatures, consuming electrolyte and generating gas. The consequences include increased internal resistance, shortened lifespan, and in more serious cases, casing rupture, leakage, and even fire and explosion. Capacity loss manifests as a decreasing amount of electricity discharged from the battery. This is caused by the continuous thickening of the CEI / SEI film, irreversibly consuming the lithium source in the system; phase transitions and cation mixing causing some materials to lose their lithium storage capacity; and uneven lithium-ion concentration during high-rate charging and discharging leading to stress concentration, causing microcracks in secondary particles, generating new surface and electrolyte side reactions, and accelerating degradation. The consequence is a visibly decreasing battery range. Cyclic degradation is a phenomenon in which battery capacity continuously decreases with the increase of charge and discharge cycles. This is caused by a combination of factors such as gas generation, capacity loss, increased internal resistance, and structural degradation, which together form a vicious cycle of positive feedback, leading to the accelerated degradation of battery performance.

[0043] Step S330: In response to the temperature being greater than a first temperature threshold and / or the charge / discharge rate being greater than a first rate threshold, control the second power supply unit to supply power and control the first power supply unit to be in a sleep state.

[0044] Specifically, if the temperature exceeds a first temperature threshold and / or the charge / discharge rate exceeds a first rate threshold, it means that the current temperature and / or charge / discharge rate is high. In this case, if the first power supply unit 11 is used for power supply, the risk of abnormal situations such as gas generation, capacity loss, or cycle degradation in the first power supply unit 11 is high. Based on this, the battery management system 13 switches to the second power supply unit 12 for power supply and stops the first power supply unit 11 from supplying power, thereby reducing the risk of abnormal situations such as gas generation, capacity loss, or cycle degradation in the first power supply unit 11 and extending the service life of the first power supply unit 11. Secondly, since the second power supply unit 12, which has better high-temperature stability, is used for power supply, the stability and safety of the power supply to the battery pack 10 can be improved.

[0045] Optionally or additionally, the first temperature threshold is 45°C. When the temperature is greater than 45°C, the first power supply unit 11 is at higher risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation, and these abnormal conditions may rapidly worsen. Therefore, by setting the first temperature threshold to 45°C, timely intervention measures can be taken to effectively reduce the above risks and extend the service life of the battery pack 10.

[0046] Optionally or additionally, the first rate threshold is 8C. When the charge / discharge rate is greater than 8C, the first power supply unit 11 is at higher risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation, and these abnormal conditions may rapidly worsen. Therefore, by setting the first temperature threshold to 8C, timely intervention measures can be taken to effectively reduce the above risks and extend the service life of the battery pack 10.

[0047] Please refer to Figure 4 , Figure 4 Another flowchart illustrates the method performed by the battery management system 13 provided in this embodiment of the application. Figure 4 As shown, the battery management system 13 is configured to perform steps S410 to S440.

[0048] Step S410: Obtain the temperature and charge / discharge rate of the battery pack.

[0049] The specific implementation process of step S410 is the same as that of step S310.

[0050] Step S420: In response to the temperature being less than or equal to a first temperature threshold and the charge / discharge rate being less than or equal to a first rate threshold, control the first power supply unit to supply power and control the second power supply unit to be in a sleep state.

[0051] The specific implementation process of step S420 is the same as that of step S320.

[0052] Step S430: In response to the charge / discharge rate being greater than a first rate threshold, and / or in response to the temperature being greater than a first temperature threshold, and the current state of charge of the first power supply unit being less than or equal to a first state of charge threshold, control the second power supply unit to supply power, and control the first power supply unit to enter a sleep state.

[0053] The specific implementation process of step S330 includes step S430.

[0054] Specifically, if the charge / discharge rate is greater than the first rate threshold, the first power supply unit 11 can be directly controlled to enter a sleep state. At this time, since the first power supply unit 11 enters a sleep state, the charge / discharge rate drops to zero, and the risk of abnormal situations such as gas generation, capacity loss or cycle decay of the first power supply unit 11 is low, which is conducive to extending the service life of the first power supply unit 11.

[0055] If the temperature exceeds a first temperature threshold, and the current state of charge (SOC) of the first power supply unit 11 is less than or equal to the first SOC threshold, the first power supply unit 11 can also be controlled to enter a sleep state. In this state, because the current SOC of the first power supply unit 11 is low, even if the temperature is too high, the risk of abnormal conditions such as gas generation, capacity loss, or cycle decay is low, thus helping to extend the service life of the first power supply unit 11. Here, the state of charge (SOC) refers to the ratio of the current remaining charge of the first power supply unit 11 to its total capacity when fully charged.

[0056] The first state of charge threshold is a preset state of charge threshold, which can be set based on the actual application scenario. Optionally or additionally, the first state of charge threshold is 30%. When the temperature is greater than the first temperature threshold, if the current state of charge of the first power supply unit 11 is less than or equal to 30%, then after controlling the first power supply unit 11 to enter a dormant state, the risk of abnormal situations such as gas generation, capacity loss, or cycle decay due to excessive temperature is reduced, thereby helping to extend the service life of the first power supply unit 11.

[0057] Step S440: In response to the temperature being greater than the first temperature threshold and the current state of charge of the first power supply unit being greater than the first state of charge threshold, control the first power supply unit to discharge until the state of charge of the first power supply unit is less than or equal to the second state of charge threshold, control the second power supply unit to supply power, and control the first power supply unit to enter a sleep state.

[0058] The specific implementation process of step S330 includes step S440.

[0059] Specifically, when the temperature exceeds a first temperature threshold and the current state of charge (SBC) of the first power supply unit is also greater than the first SBC threshold, directly controlling the first power supply unit 11 to enter a dormant state would still pose a high risk of abnormalities such as gas generation, capacity loss, or cycle degradation due to excessively high temperature. Therefore, this embodiment first controls the first power supply unit 11 to discharge, thereby reducing its SBC. Once the SBC is reduced to less than or equal to a second SBC threshold, the first power supply unit 11 can be controlled to enter a dormant state. At this point, because the current SBC is lower, even if the temperature is too high, the risk of abnormalities such as gas generation, capacity loss, or cycle degradation is also lower, thus extending the service life of the first power supply unit 11.

[0060] The second state-of-charge threshold is a preset state-of-charge threshold, which can be set based on the actual application scenario. Optionally or additionally, the second state-of-charge threshold is 0. When the temperature is higher than the first temperature threshold, by reducing the state of charge of the first power supply unit 11 to 0, the risk of abnormal situations such as gas generation, capacity loss, or cycle decay caused by excessive temperature can be effectively reduced after the first power supply unit 11 is controlled to enter a dormant state, thereby helping to extend the service life of the first power supply unit 11.

[0061] The following explanation of the application's effectiveness is based on test results from three different battery packs.

[0062] The three battery packs are battery pack B1, battery pack B2, battery pack B3 and battery pack B4, and the rated capacity of each of them is 5000mAh.

[0063] Battery pack B1 is designed according to the method provided in the embodiments of this application. The molar percentage of nickel in the first lithium transition metal oxide in the cathode electrode of the first power supply unit of battery pack B1 is 90%, and the molar percentage of nickel in the second lithium transition metal oxide in the cathode electrode of the second power supply unit of battery pack B1 is 50%. Battery pack B1 is capable of performing... Figure 3 and Figure 4 The steps are shown.

[0064] Battery pack B2 includes two power supply units, and the molar percentage of nickel in the lithium transition metal oxide in the cathode electrode of both power supply units is 90%.

[0065] Battery pack B3 includes two power supply units. In one power supply unit, the molar percentage of nickel in the lithium transition metal oxide in the cathode electrode is 90%, and in the other power supply unit, the molar percentage of nickel in the lithium transition metal oxide in the cathode electrode is 50%.

[0066] Battery pack B4 includes two power supply units, and the molar percentage of nickel in the lithium transition metal oxide in the cathode electrode of both power supply units is 50%.

[0067] It is understandable that, apart from the difference in lithium transition metal oxides in their respective cathode electrodes, battery packs B1, B2, B3, and B4 have the same other components and proportions, anode electrode composition and proportions, N / P ratios of the cathode and anode, separators, electrolytes, and other designs, which are matched with the cell capacity.

[0068] With the first temperature threshold set to 45℃ and the first rate threshold set to 8C, battery pack B1 underwent the following tests: Capacity retention, cycle expansion, and cycle life testing: The initial battery pack was placed in a 25°C environment and charged to 4V with a constant current of 3C. Then, it was charged at 4V with a constant voltage until the charging current decreased to 1C. Next, it was charged at 1C with a constant current until the voltage reached 4.35V. Finally, it was charged at 4.35V with a constant voltage until the current decreased to 0.05C, and then left to stand for 15 minutes. Subsequently, the first power supply unit in the battery pack was powered, while the second power supply unit was in a dormant state. The first power supply unit was discharged at a discharge rate of 3C until its voltage reached 2.5V, and then left to stand for 15 minutes. This process was repeated 40 times. In the first cycle, after discharging the first power supply unit to its voltage of 2.5V, the second power supply unit was discharged at a constant voltage of 4.35V until it reached 2.5V. The total discharge capacity was recorded, which is the initial discharge capacity C0 of the battery pack. The ambient temperature was adjusted to 50℃, allowing the second power supply unit in the battery pack to operate while the first power supply unit remained in sleep mode (because the ambient temperature was higher than the first temperature threshold). The battery pack was charged at a constant current of 3C to a voltage of 4V. Then, it was charged at 4V with a constant voltage until the charging current decreased to 1C. Next, it was charged at 1C with a constant current until a voltage of 4.35V was achieved. Finally, it was charged at 4.35V with a constant voltage until the current decreased to 0.05C, and then left to stand for 15 minutes. Subsequently, the second power supply unit was discharged at a discharge rate of 3C until its voltage reached 2.5V, and then left to stand for 15 minutes. This process was repeated 10 times as one cycle. The above process (40 cycles at 25℃ + 10 cycles at 50℃) constitutes one cycle, and the above process is repeated 10 times.

[0069] After the battery pack is fully charged (both the first and second power supply units are fully charged) in the 500th cycle, the temperature of the battery pack is reduced to 25°C, and then the battery pack (both the first and second power supply units) is discharged at a discharge rate of 3C until their voltage is 2.5V. After resting for 15 minutes, the discharge capacity of the battery pack is recorded as C1. The capacity retention rate of the battery pack after the 500th cycle is then calculated as C1 / C0×100%.

[0070] The initial battery pack was placed in a 25°C environment, and its voltage was adjusted to half of its full charge (4.35V). The initial thickness of the battery pack at this point was measured and recorded as T0. Then, based on the above charge-discharge cycle (40 cycles at 25°C + 10 cycles at 50°C), the battery pack was cycled for 500 cycles. After reaching 500 cycles, the battery pack was fully charged again in a 25°C environment (4.35V), and its thickness at this point was measured and recorded as T2. The cycle expansion rate after the 500th cycle is: Cycle expansion rate = T2 / T0 × 100%.

[0071] The cycle life of a battery pack is determined by the number of cycles when the capacity retention rate is not less than 80% and the cycle expansion rate is not more than 30%.

[0072] Energy density test: The battery pack was placed in a 25℃ environment and charged at a constant current of 0.5C to a voltage of 4.35V. Then, it was charged at 4.35V under constant voltage until the current decreased to 0.05C, and allowed to stand for 15 minutes. Subsequently, it was discharged at a constant current of 0.5C until the battery pack voltage reached 2.5V, and allowed to stand for 30 minutes. The capacity C and energy value E released by each cell were recorded; the weight of the battery pack was measured and recorded as m. The energy density of the battery pack was calculated as: Energy density of battery pack = E / m.

[0073] Battery packs B2, B3, and B4 will each undergo the following tests: Capacity retention, cycle expansion, and cycle life testing: The initial battery pack was placed in a 25°C environment and charged at a constant current of 3C to a voltage of 4V. Then, it was charged at 4V with a constant voltage until the charging current decreased to 1C. Next, it was charged at 1C with a constant current until the voltage reached 4.35V. Finally, it was charged at 4.35V with a constant voltage until the current decreased to 0.05C, and then left to stand for 15 minutes. Subsequently, the battery pack (two power supply units) was discharged at a discharge rate of 3C to a voltage of 2.5V, and left to stand for 15 minutes. This process was repeated for 40 cycles, and the total discharge capacity of the battery pack in the first cycle was recorded, which is the initial discharge capacity C0 of the battery pack. Place the battery pack in a 45°C environment and charge it (containing two power supply units) to 4V with a constant current of 3C. Then, charge the battery pack at 4V with a constant voltage until the charging current decreases to 1C. Then, charge the battery pack at 1C with a constant current until the voltage reaches 4.35V. Finally, charge the battery pack at 4.35V with a constant voltage until the current decreases to 0.05C. Let it stand for 15 minutes. Then, discharge the battery pack (containing two power supply units) at a constant current of 3C until the voltage reaches 2.5V. Let it stand for 15 minutes. This is one cycle. Repeat the above process 10 times.

[0074] The above process (40 cycles at 25℃ + 10 cycles at 50℃) constitutes one cycle, and the above process is repeated 10 times.

[0075] After the battery pack was fully charged (both power supply units were fully charged) in the 500th cycle, the temperature of the battery pack was reduced to 25℃, and then the battery pack (both power supply units) was discharged at a discharge rate of 3C until its voltage was 2.5V. After resting for 15 minutes, the discharge capacity of the battery pack was recorded as C1. The capacity retention rate of the battery pack after the 500th cycle was calculated as: Capacity retention rate = C1 / C0 × 100%.

[0076] The battery pack was placed in a 25°C environment, and its voltage was adjusted to half of its full charge (4.35V). The initial thickness of the battery pack at this point was measured and recorded as T0. Then, based on the above charge-discharge cycle (40 cycles at 25°C + 10 cycles at 50°C), the battery pack was cycled for 500 cycles. After reaching 500 cycles, the battery pack was fully charged again in a 25°C environment (4.35V), and its thickness at this point was measured and recorded as T2. The cycle expansion rate after the 500th cycle is: Cycle expansion rate = T2 / T0 × 100%.

[0077] The cycle life of a battery pack is determined by the number of cycles when the capacity retention rate is not less than 80% and the cycle expansion rate is not more than 30%.

[0078] Energy density test: The battery pack was placed in a 25℃ environment and charged at a constant current of 0.5C to a voltage of 4.35V. Then, it was charged at 4.35V under constant voltage until the current decreased to 0.05C. After resting for 15 minutes, it was discharged at a constant current of 0.5C until the battery pack voltage reached 2.5V. After resting for 30 minutes, the capacity C and energy value E released by each cell were recorded. The weight of the battery pack was measured and recorded as m. The energy density of the battery pack was calculated as: Energy density of battery pack = E / m.

[0079] The test results are shown in Table 1 below: Table 1

[0080] For battery packs B1 and B3, both use two power supply units with the same nickel content. The difference lies in the charging and discharging process of battery pack B1, which uses the method executed by the battery management system provided in this application embodiment, while battery pack B3 uses a conventional charging and discharging process. For battery packs B2, B3, and B4, all three use a conventional charging and discharging process, the difference being that the nickel content of the two power supply units in the three battery packs is different. According to Table 1, the capacity retention rate, cycle expansion rate, and cycle life of battery pack B1 are all superior to those of battery packs B2, B3, and B4. Obviously, the method executed by the battery management system provided in this application embodiment (i.e., Figure 3 and Figure 4 The method shown can extend the cycle life of the battery pack.

[0081] In summary, the battery pack provided in this application embodiment has, on the one hand, high energy density, long cycle life, and high safety by employing two power supply units, one of which includes a cathode electrode with a high nickel content; on the other hand, by improving the method of execution of the battery management system, the energy density, cycle life, and safety of the battery pack can be further improved.

[0082] This application also provides an electrical device. The electrical device includes a load and a battery pack as described in any embodiment of this application, the battery pack being used to supply power to the load.

[0083] Loads include electrical components on electrical equipment such as motors, lights, horns, and instruments. Electrical equipment refers to devices that require battery power. Examples of electrical equipment include: unmanned aerial vehicles, energy storage products, power tools, and electric vehicles (electric two-wheelers, electric tricycles), etc.

[0084] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

[0085] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, and the steps can be implemented in any order. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A battery pack, characterized in that, include: The first power supply unit includes a first cathode electrode, which includes a first lithium transition metal oxide containing nickel. Based on the total number of moles of metal atoms other than Li atoms in the active material of the first cathode electrode, the molar percentage of nickel in the first lithium transition metal oxide is greater than a first content threshold. The second power supply unit includes a second cathode electrode, which includes a second lithium transition metal oxide containing nickel. Based on the total number of moles of metal atoms other than Li atoms in the active material of the second cathode electrode, the molar percentage of nickel in the second lithium transition metal oxide is less than or equal to the first content threshold. The battery management system is configured as follows: Obtain the temperature and charge / discharge rate of the battery pack; In response to the temperature being less than or equal to a first temperature threshold and the charge / discharge rate being less than or equal to a first rate threshold, the first power supply unit is controlled to supply power, and the second power supply unit is controlled to be in a sleep state. In response to the temperature being greater than the first temperature threshold, and / or the charge / discharge rate being greater than the first rate threshold, the second power supply unit is controlled to supply power, and the first power supply unit is controlled to be in a sleep state.

2. The battery pack according to claim 1, characterized in that, The first content threshold is 85%.

3. The battery pack according to claim 1, characterized in that, The ratio of the capacity of the first power supply unit to the total capacity is 70%-85%, wherein the total capacity is the sum of the capacities of the first power supply unit and the second power supply unit.

4. The battery pack according to any one of claims 1-3, characterized in that, The response to the temperature being greater than the first temperature threshold, and / or the charge / discharge rate being greater than the first charge / discharge threshold, controlling the second power supply unit to supply power, and controlling the first power supply unit to be in a sleep state, includes: In response to the temperature being greater than the first temperature threshold and the current state of charge of the first power supply unit being less than or equal to the first state of charge threshold, the first power supply unit is controlled to enter a sleep state.

5. The battery pack according to claim 4, characterized in that, The first state of charge threshold is 30%.

6. The battery pack according to any one of claims 1-3, characterized in that, The response to the temperature being greater than the first temperature threshold, and / or the charge / discharge rate being greater than the first charge / discharge threshold, controlling the second power supply unit to supply power, and controlling the first power supply unit to be in a sleep state, includes: In response to the temperature being greater than the first temperature threshold and the current state of charge of the first power supply unit being greater than the first state of charge threshold, the first power supply unit is controlled to discharge. In response to the first power supply unit discharging until the state of charge of the first power supply unit is less than or equal to the second state of charge threshold, the first power supply unit is controlled to enter a sleep state.

7. The battery pack according to claim 6, characterized in that, The second state of charge threshold is 0.

8. The battery pack according to any one of claims 1-7, characterized in that, The first temperature threshold is 45°C.

9. The battery pack according to any one of claims 1-7, characterized in that, The first multiplier threshold is 8C.

10. The battery pack according to any one of claims 1-9, characterized in that, The specific capacity of the first lithium transition metal oxide is 205-215 mAh / g, and / or the specific capacity of the second lithium transition metal oxide is 100-204 mAh / g.

11. An electrical appliance, characterized in that, Includes the load and the battery pack as described in any one of claims 1-10.

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