Battery pack and electric equipment

Abstract

A battery pack includes: a first power supply unit including a first cathode tab, the 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, the second cathode pole piece comprises 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 of the battery pack; controlling the first power supply unit and the second power supply unit to charge at a first charging rate and discharge at a first discharging rate respectively in response to the condition that the temperature is less than or equal to a first temperature threshold value; in response to the fact that the temperature is larger than the first temperature threshold value, the charging multiplying power and the discharging multiplying power of the first power supply unit and the second power supply unit are reduced, and the charging upper limit voltage of the first power supply unit and the second power supply unit is reduced.

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, mainly composed of lithium iron phosphate, lithium manganese oxide, lithium cobalt oxide, and other ternary batteries containing nickel, cobalt, and manganese. These batteries 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, including 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 mass 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 mass 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 of the battery pack before each charging or discharging cycle; control the first power supply unit and the second power supply unit to charge and discharge at a first charging rate and a first discharging rate, respectively, in response to a temperature less than or equal to the first temperature threshold; and reduce the charging and discharging rates of the first and second power supply units, and reduce the upper limit voltage for charging the first and second power supply units, in response to a temperature greater than the first temperature threshold.

[0006] A higher molar percentage of nickel in the first lithium transition metal oxide (LiTO) indicates a higher nickel content, resulting in a higher energy density for the battery pack. A temperature less than or equal to the first temperature threshold indicates a lower ambient temperature for the battery pack. In this case, the risk of abnormalities in the first and second power supply units due to ambient temperature is lower, such as gas generation, capacity loss, or cycle degradation in the first power supply unit. Therefore, the first and second power supply units are controlled to charge at the originally designed charging rate (i.e., the first charging rate) or discharge at the originally designed discharging rate (i.e., the first discharging rate). A temperature greater than the first temperature threshold indicates a higher ambient temperature for the battery pack. In this case, the risk of abnormalities in the first power supply unit due to excessive temperature, such as gas generation, capacity loss, or cycle degradation, is higher. Therefore, the charging and discharging rates of the first and second power supply units are first reduced to decrease temperature rise. Simultaneously, the upper limit voltage for charging the first and second power supply units is reduced to decrease the risk of abnormalities such as gas generation, capacity loss, or cycle degradation.

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

[0008] In one or more embodiments, the capacity ratio of the first power supply unit and the second power supply unit is 1-1.5.

[0009] In one or more embodiments, in response to a temperature greater than a first temperature threshold, reducing the charging rate and discharging rate of the first power supply unit and the second power supply unit includes: in response to a temperature greater than the first temperature threshold and less than or equal to a second temperature threshold, the first power supply unit and the second power supply unit are charged at a second charging rate and discharged at a second discharging rate, wherein the second charging rate is less than the first charging rate and the second discharging rate is less than the first discharging rate.

[0010] In one or more embodiments, the second charging rate is 50%-80% of the first charging rate, and the second discharging rate is 60%-80% of the first discharging rate.

[0011] Setting the second charging rate to 50%-80% of the first charging rate can effectively reduce temperature and significantly reduce risk while maintaining optimal performance. Setting the second discharging rate to 60%-80% of the first discharging rate can maintain basic functions, effectively reduce temperature, and significantly reduce risk.

[0012] In one or more embodiments, reducing the upper limit voltage for charging the first power supply unit and the second power supply unit includes: in response to a temperature greater than a first temperature threshold and less than or equal to a second temperature threshold, configuring the upper limit voltage for charging the first power supply unit and the second power supply unit to a second upper limit voltage, wherein the second upper limit voltage is less than the first upper limit voltage, and the first upper limit voltage is the upper limit voltage for charging the first power supply unit and the second power supply unit when the temperature is less than or equal to the first temperature threshold.

[0013] Reducing the upper limit voltage for charging the first and second power supply units from the first upper limit voltage to the second upper limit voltage can reduce the risk of abnormal situations such as gas generation, capacity loss, or cycle decay in the first and second power supply units.

[0014] In one or more embodiments, the state of charge corresponding to the second upper limit voltage is 90%-99% of the state of charge corresponding to the first upper limit voltage.

[0015] In one or more embodiments, in response to a temperature greater than a first temperature threshold, the charging rate and discharging rate of the first power supply unit and the second power supply unit are reduced, further comprising: in response to a temperature greater than a second temperature threshold and less than or equal to a third temperature threshold, performing the following steps: in response to a 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; or, in response to a 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, and then, in response to the first power supply unit discharging until its state of charge is less than or equal to a second state of charge threshold, controlling the first power supply unit to enter a sleep state.

[0016] When the temperature is greater than the second temperature threshold and less than or equal to the third temperature threshold, and the current state of charge (SBC) of the first power supply unit is less than or equal to the first SBC threshold, the first power supply unit is controlled to enter a sleep state. In this case, because the current SBC of the first power supply unit is low, the risk of abnormal conditions such as gas generation, capacity loss, or cycle decay is low even if the temperature is too high, thus helping to extend the service life of the first power supply unit. When the temperature is greater than the second temperature threshold and less than or equal to the third temperature threshold, and the current SBC of the first power supply unit is greater than the first SBC threshold, the first power supply unit is first controlled to discharge to reduce its SBC. This continues until the SBC of the first power supply unit decreases to less than or equal to the second SBC threshold, at which point the first power supply unit is controlled to enter a sleep state. At this point, because the current SBC of the first power supply unit is low, the risk of abnormal conditions such as gas generation, capacity loss, or cycle decay is low even if the temperature is too high, thus helping to extend the service life of the first power supply unit.

[0017] In one or more embodiments, the first state of charge threshold is 30%, and / or the second state of charge threshold is 0.

[0018] In one or more embodiments, in response to a temperature greater than a first temperature threshold, the charging rate and discharging rate of the first power supply unit and the second power supply unit are reduced, and the method further includes: in response to a temperature greater than a third temperature threshold, controlling the first power supply unit and the second power supply unit to enter a sleep state.

[0019] A temperature exceeding the third temperature threshold indicates excessive heat. Regardless of the operating state of the first and second power supply units, this excessive heat poses a risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation. Therefore, at this point, the first and second power supply units are controlled to enter a sleep state, ceasing power supply to reduce risks and extend the battery pack's lifespan.

[0020] In one or more embodiments, the first temperature threshold is 35°C, and / or the second temperature threshold is 45°C, and / or the third temperature threshold is 60°C.

[0021] Secondly, embodiments of this application provide an electrical device, which includes a load and the battery pack mentioned in the first aspect. Attached Figure Description

[0022] 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.

[0023] 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 schematic diagram of the method executed by the battery management system provided in the embodiments of this application. Figure 1 ; Figure 4 This is a schematic diagram of the method executed by the battery management system provided in the embodiments of this application. Figure 2 . Detailed Implementation

[0024] 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.

[0025] 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.

[0026] 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.

[0027] Please refer to Figure 1 , Figure 1 One battery structure 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 capacity of the second power supply unit 12 (i.e., the capacity ratio) is 1-1.5, meaning that the capacity of the first power supply unit 11 is at least equal to the capacity of the second power supply unit 12, and at most 1.5 times the capacity of 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 an auxiliary power supply unit to ensure the battery has 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] Based on the total molar mass of all 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. Specifically, based on the mass of the active material in the first cathode electrode 111, the calculation benchmark is clarified as the mass of the active material, 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) in the active material relative to the total number of transition metal atoms (such as Ni, Mn, Co, Al, etc.). 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.

[0032] 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.

[0033] 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.

[0034] 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. It is clear that the calculation basis is the mass of the active material in the second cathode electrode 121, not the mass of the entire electrode. Therefore, the molar percentage of nickel refers to 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.

[0035] 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 the activity per unit mass of material, expressed in mAh / g. A specific capacity of 205-215 mAh / g for the first lithium transition metal oxide indicates a relatively 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.

[0036] 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.

[0037] Step S310: Obtain the temperature of the battery pack before each charge or discharge.

[0038] The battery management system 13 typically monitors the temperature of the battery pack 10 using a thermistor (such as an NTC or PTC). Since this is done before each charge or discharge of the battery pack 10, the temperature of the battery pack 10 can be approximated to or equal to the temperature of the environment in which the battery pack 10 is located. In other words, the temperature of the battery pack 10 is equivalent to the temperature of the environment in which the battery pack 10 is located.

[0039] Step S320: In response to the temperature being less than or equal to a first temperature threshold, control the first power supply unit and the second power supply unit to charge at a first charging rate and discharge at a first discharging rate, respectively.

[0040] The first temperature threshold is a preset temperature threshold, and the first charging rate and the first discharging rate are preset rates. All three can be set based on the actual application scenario, and this application embodiment does not impose specific restrictions on them.

[0041] Specifically, a temperature less than or equal to the first temperature threshold means that the ambient temperature of the battery pack 10 is low. Under these conditions, the risk of abnormal situations occurring in the first power supply unit 11 and the second power supply unit 12 due to ambient temperature is low. For example, the risk of abnormal situations such as gas generation, capacity loss, or cycle degradation in the first power supply unit 11 is low. Therefore, the first power supply unit 11 and the second power supply unit 12 are controlled to charge at the originally designed charging rate (i.e., the first charging rate) or discharge at the originally designed discharging rate (i.e., the first discharging rate). That is, if the first power supply unit 11 and the second power supply unit 12 need to be charged, they are charged at the charging rate (i.e., the first charging rate) under normal conditions; if the first power supply unit 11 and the second power supply unit 12 need to be discharged, they are discharged at the discharging rate (i.e., the first discharging rate) under normal conditions. In summary, when the temperature is less than the first temperature threshold, the charging rate and discharging rate of the first power supply unit 11 and the second power supply unit 12 are not adjusted.

[0042] 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, reduce the charging rate and discharging rate of the first power supply unit and the second power supply unit, and reduce the upper limit voltage for charging the first power supply unit and the second power supply unit.

[0044] Specifically, a temperature exceeding the first temperature threshold indicates a high ambient temperature for the battery pack 10. Under such conditions, the first power supply unit 11 is at higher risk of experiencing abnormalities such as gas generation, capacity loss, or cycle degradation due to excessive temperature. Therefore, firstly, the charging and discharging rates of the first and second power supply units 11 and 12 are reduced. Specifically, if the first and second power supply units 11 and 12 need charging, their charging rates are reduced (based on the first charging rate); if they need discharging, their discharging rates are reduced (based on the first discharging rate). This reduces temperature rise. Simultaneously, the upper limit voltage for charging the first and second power supply units 11 and 12 is lowered to reduce the risk of abnormalities such as gas generation, capacity loss, or cycle degradation.

[0045] 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 S480.

[0046] Step S410: Obtain the temperature of the battery pack before each charge or discharge.

[0047] The specific implementation process of step S410 is the same as that of step S310.

[0048] Step S420: In response to the temperature being less than or equal to a first temperature threshold, control the first power supply unit and the second power supply unit to charge at a first charging rate and discharge at a first discharging rate, respectively.

[0049] The specific implementation process of step S420 is the same as that of step S320.

[0050] Step S430: In response to a temperature greater than a first temperature threshold and less than or equal to a second temperature threshold, the first power supply unit and the second power supply unit charge at a second charging rate and discharge at a second discharging rate.

[0051] The specific implementation process of step S330 includes step S430.

[0052] The second charging rate is less than the first charging rate, and the second discharging rate is less than the first discharging rate. The second temperature threshold is a preset temperature threshold that can be set based on the actual application scenario, and the second temperature threshold is greater than the first temperature threshold.

[0053] Specifically, if the temperature is greater than the first temperature threshold and less than or equal to the second temperature threshold, it means that the temperature increase is small. It is only necessary to reduce the charging rate of the first power supply unit 11 and the second power supply unit 12 from the first charging rate to the second charging rate, and reduce the discharging rate of the first power supply unit 11 and the second power supply unit 12 from the first discharging rate to the second discharging rate, so as to reduce the risk of abnormal situations such as gas generation, capacity loss or cycle decay of the first power supply unit 11 due to excessive temperature.

[0054] Optionally or additionally, the second charging rate is 50%-80% of the first charging rate, and the second discharging rate is 60%-80% of the first discharging rate.

[0055] Setting the second charging rate to less than 50% of the first charging rate results in poor system utilization, slow charging speed, and a poor user experience. Conversely, setting the second charging rate to more than 80% of the first charging rate leads to excessive heat generation in the battery pack 10, making it difficult to effectively reduce the temperature. Therefore, setting the second charging rate to 50%-80% of the first charging rate effectively reduces temperature while maintaining optimal performance and significantly reduces risk.

[0056] Setting the second discharge rate to less than 60% of the first discharge rate will result in a significant performance degradation, noticeable to users (e.g., electric vehicles using this battery pack will feel weak), leading to a poor user experience. Conversely, setting the second discharge rate to more than 80% of the first discharge rate will result in the battery pack still generating considerable heat, making it difficult to effectively reduce the temperature. Therefore, setting the second discharge rate to 60%-80% of the first discharge rate maintains basic functionality, effectively reduces temperature, and significantly mitigates risk.

[0057] Step S440: In response to a temperature greater than a first temperature threshold and less than or equal to a second temperature threshold, the upper limit voltage for charging the first power supply unit and the second power supply unit is configured as the second upper limit voltage.

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

[0059] Wherein, the second upper limit voltage is less than the first upper limit voltage, and the first upper limit voltage is the upper limit voltage for charging the first power supply unit and the second power supply unit when the temperature is less than or equal to the first temperature threshold.

[0060] Reducing the upper limit voltage for charging the first power supply unit 11 and the second power supply unit 12 from the first upper limit voltage to the second upper limit voltage can reduce the risk of abnormal situations such as gas generation, capacity loss or cycle decay in the first power supply unit 11 and the second power supply unit 12.

[0061] Optionally or additionally, the state of charge corresponding to the second upper limit voltage is 90%-99% of the state of charge corresponding to the first upper limit voltage.

[0062] The State of Charge (SOC) is the ratio of the battery's current remaining charge to its rated capacity when fully charged. The SOC corresponding to the first upper limit voltage refers to the state of charge of the first power supply unit 11 and the second power supply unit 12 when the voltage of the first power supply unit 11 and the second power supply unit 12 is at the first upper limit voltage; the SOC corresponding to the second upper limit voltage refers to the state of charge of the first power supply unit 11 and the second power supply unit 12 when the voltage of the first power supply unit 11 and the second power supply unit 12 is at the second upper limit voltage.

[0063] If the state of charge (SOC) corresponding to the second upper limit voltage is less than 90% of the SOC corresponding to the first upper limit voltage, the battery pack loses too much energy, resulting in low capacity utilization. Conversely, setting the SOC corresponding to the second upper limit voltage to be less than or equal to 99% of the SOC corresponding to the first upper limit voltage can improve capacity utilization while reducing risk. Therefore, setting the SOC corresponding to the second upper limit voltage to 90%-99% of the SOC corresponding to the first upper limit voltage can simultaneously balance capacity utilization and risk reduction.

[0064] Step S450: In response to the temperature being greater than the third temperature threshold, control the first power supply unit and the second power supply unit to enter a sleep state. The specific implementation process of step S330 includes step S450.

[0065] Specifically, a temperature exceeding the third temperature threshold indicates excessive heat. Regardless of the operating state of the first power supply unit 11 and the second power supply unit 12, there is a risk of abnormal situations such as gas generation, capacity loss, or cycle decay due to excessive heat. Therefore, at this time, the first power supply unit 11 and the second power supply unit 12 are controlled to enter a sleep state, and the first power supply unit 11 and the second power supply unit 12 stop supplying power.

[0066] Optionally or additionally, after the first power supply unit 11 and the second power supply unit 12 enter the sleep state, an alarm signal can be output to notify the user to remind the user to use the battery pack 10 after the temperature drops.

[0067] The third temperature threshold is a pre-set temperature threshold that can be set based on the actual application scenario, and the third temperature threshold is greater than the second temperature threshold.

[0068] Optionally or additionally, the first temperature threshold is 35°C, and / or the second temperature threshold is 45°C, and / or the third temperature threshold is 60°C. When the temperature is greater than 35°C, the high temperature may begin to affect the first power supply unit 11 and the second power supply unit 12. In this case, simply reducing the charging rate and discharging rate of the first power supply unit 11 and the second power supply unit 12 (without reducing them to 0) can effectively reduce the risk. When the temperature is greater than 45°C, the first power supply unit 11 has a higher risk of abnormal conditions such as gas generation, capacity loss, or cycle decay, and these abnormal conditions may rapidly intensify. In this case, controlling the first power supply unit 11 to enter a dormant state based on its state of charge can effectively reduce the risk. When the temperature is greater than 60°C, the first power supply unit 11 and the second power supply unit 12 have a higher risk of abnormal conditions such as gas generation, capacity loss, or cycle decay, and these abnormal conditions may rapidly intensify. In this case, it is necessary to control both the first power supply unit 11 and the second power supply unit 12 to enter a dormant state to effectively reduce the risk.

[0069] Step S460: In response to the temperature being greater than the second temperature threshold and less than or equal to the third 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.

[0070] The specific implementation process of step S330 includes step S460. It can be understood that when executing step S460, the state of the second power supply unit 12 remains unchanged, that is, no other processing is done on the second power supply unit 12, and only the first power supply unit 11 is switched to a sleep state.

[0071] Specifically, a temperature greater than the second temperature threshold but less than or equal to the third temperature threshold indicates a higher risk of abnormal conditions such as gas generation, capacity loss, or cycle degradation in the first power supply unit 11. This is because the nickel content in the first lithium transition metal oxide of the first power supply unit 11 is relatively high, so when the temperature rises, the first power supply unit 11 is the first to be significantly affected. At this point, with the current state of charge of the first power supply unit 11 less than or equal to the first state of charge threshold, the first power supply unit 11 is controlled to enter a sleep state, and it stops supplying power. In this case, because the current state of charge 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 degradation is also low, thus helping to extend the service life of the first power supply unit 11.

[0072] The first state-of-charge threshold is a preset threshold that 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 second temperature threshold and less than or equal to the third 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.

[0073] Step S470: In response to the temperature being greater than the second temperature threshold and less than or equal to the third 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.

[0074] Step S480: 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, control the first power supply unit to enter a sleep state.

[0075] The specific implementation process of step S330 includes steps S470 to S480. It can be understood that when executing steps S470 and S480, the state of the second power supply unit 12 remains unchanged, that is, no other processing is performed on the second power supply unit 12.

[0076] Specifically, when the temperature is greater than the second temperature threshold and less than or equal to the third temperature threshold, and the current state of charge (SOC) of the first power supply unit 11 is greater than the first SOC threshold, directly controlling the first power supply unit 11 to enter a sleep state would still pose a high risk of abnormalities such as gas generation, capacity loss, or cycle decay due to excessively high temperature, since the current SOC of the first power supply unit 11 is greater than the first SOC threshold. Therefore, this embodiment first controls the first power supply unit 11 to discharge, thereby reducing the SOC of the first power supply unit 11. Until the SOC of the first power supply unit 11 is reduced to less than or equal to the second SOC threshold, the first power supply unit 11 is controlled to enter a sleep state. At this point, because the current SOC of the first power supply unit 11 is lower, even if the temperature is too high, the risk of abnormalities such as gas generation, capacity loss, or cycle decay is also lower, thus helping to extend the service life of the first power supply unit 11.

[0077] 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.

[0078] The effectiveness of this application is illustrated below based on test results from three different battery packs.

[0079] 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.

[0080] 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 method and steps shown; Battery pack B2 includes two power supply units, and the molar percentage of nickel in the lithium transition metal oxide in the cathode of the two power supply units is 90%.

[0081] 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%.

[0082] Battery pack B4 includes two power supply units, and the molar percentage of nickel in the lithium transition metal oxide in the cathode of the two power supply units is 50%.

[0083] 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.

[0084] With the first temperature threshold set to 35°C and the second temperature threshold set to 45°C, 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 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 battery pack (including the first and second 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 40 times. In the first cycle, the total discharge capacity after discharging the battery pack to 2.5V was recorded, which is the initial discharge capacity C0 of the battery pack. Next, the battery pack is placed in a 40°C environment. Since the ambient temperature is higher than the first temperature threshold but lower than the second temperature threshold, the first and second power supply units are set to charge at the second charging rate and discharge at the second discharging rate. For example, the second charging rate is set to 60% of the first charging rate, and the second discharging rate is set to 60% of the first discharging rate. Specifically, the battery pack (including the first and second power supply units) is charged to 4V with a constant current of 3C*60%. Then, it is charged at 4V with a constant voltage until the charging current decreases to 1C. Next, it is charged at 1C*60% with a constant current until the voltage reaches 4.35V. Finally, it is charged at 4.35V with a constant voltage until the current decreases to 0.05C. After resting for 15 minutes, the battery pack (including the first and second power supply units) is discharged at a 3C*60% discharging rate until the voltage reaches 2.5V. After resting for 15 minutes, this is considered one cycle, and the above process is repeated 10 times. The above process (40 cycles at 25℃ + 10 cycles at 40℃) constitutes one cycle, and the above process is repeated 10 times; 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 (including the first and second power supply units) is discharged at a discharge rate of 3C until its voltage is 2.5V. After resting for 15 minutes, the discharge capacity of the battery pack after the 500th cycle is recorded as C1. The capacity retention rate of the battery pack after the 500th cycle is calculated as: Capacity retention rate = C1 / C0 × 100%.

[0085] 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 40°C), the battery pack was cycled for 500 cycles. After fully charging the battery pack in a 25°C environment (4.35V), the thickness of the battery pack at this point was measured and recorded as T2. The cycle expansion rate after the 500th cycle is: Cycle expansion rate = T2 / T0 × 100%.

[0086] The cycle life of a battery pack is determined by the number of cycles in which the capacity retention rate is not less than 80% and the cycle expansion rate is not more than 30%.

[0087] 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.

[0088] 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 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 battery pack (including the first and second 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 40 times. In the first cycle, the total discharge capacity after discharging the battery pack to 2.5V was recorded, which is the initial discharge capacity C0 of the battery pack. Next, the battery pack is placed in a 40°C environment and charged at a constant current of 3C to a voltage of 4V. Then, the battery pack is charged at a constant voltage of 4V until the charging current decreases to 1C. The battery pack is then charged at a constant current of 1C until the voltage reaches 4.35V. Finally, the battery pack is charged at 4.35V until the current decreases to 0.05C. After resting for 15 minutes, the battery pack (including the first and second power supply units) is discharged at a discharge rate of 3C until the voltage reaches 2.5V. After resting for 15 minutes, this is considered one cycle. The above process is repeated 10 times. The above process (40 cycles at 25℃ + 10 cycles at 40℃) constitutes one cycle, and the above process is repeated 10 times; 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 (including the first and second power supply units) is discharged at a discharge rate of 3C until its voltage is 2.5V. After resting for 15 minutes, the discharge capacity of the battery pack after the 500th cycle is recorded as C1. The capacity retention rate of the battery pack after the 500th cycle is calculated as: Capacity retention rate = C1 / C0 × 100%.

[0089] 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 process, the battery pack was cycled through charge and discharge cycles. After 500 cycles, the battery pack was fully charged (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%.

[0090] 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%.

[0091] 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.

[0092] The test results are shown in Table 1 below: Table 1

[0093] 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] 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.

[0098] 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 by comprising: Comprising: a first power supply unit comprising a first cathode tab comprising a first lithium transition metal oxide containing nickel element, a mole fraction of nickel element in the first lithium transition metal oxide being greater than a first content threshold based on a sum of mass moles of other metal atoms except Li atoms in active materials of the first cathode tab; a second power supply unit comprising a second cathode tab comprising a second lithium transition metal oxide containing nickel element, a mole fraction of nickel element in the second lithium transition metal oxide being less than or equal to the first content threshold based on a sum of mass moles of other metal atoms except Li atoms in active materials of the second cathode tab; a battery management system configured to: obtain a temperature of the battery pack before each charging or discharging of the battery pack; in response to the temperature being less than or equal to a first temperature threshold, control the first power supply unit and the second power supply unit to be charged at a first charging rate and discharged at a first discharging rate, respectively; in response to the temperature being greater than the first temperature threshold, reduce the charging rate and the discharging rate of the first power supply unit and the second power supply unit, and reduce an upper limit voltage of charging of the first power supply unit and the second power supply unit.

2. The battery pack of claim 1, wherein, The first content threshold is 85%.

3. The battery pack according to claim 1 or 2, characterized by, A capacity ratio of the first power supply unit and the second power supply unit is 1-1.

5.

4. The battery pack according to any one of claims 1 to 3, characterized by, The response to the temperature being greater than the first temperature threshold, reducing the charging rate and the discharging rate of the first power supply unit and the second power supply unit, comprises: in response to the temperature being greater than the first temperature threshold and less than or equal to a second temperature threshold, the first power supply unit and the second power supply unit are charged at a second charging rate and discharged at a second discharging rate, wherein the second charging rate is less than the first charging rate, and the second discharging rate is less than the first discharging rate.

5. The battery pack of claim 4, wherein, The second charging rate is 50%-80% of the first charging rate, and the second discharging rate is 60%-80% of the first discharging rate.

6. The battery pack according to any one of claims 1 to 5, characterized by, The reduction of the upper limit voltage of charging of the first power supply unit and the second power supply unit, comprises: in response to the temperature being greater than the first temperature threshold and less than or equal to a second temperature threshold, the upper limit voltage of charging of the first power supply unit and the second power supply unit is configured to be a second upper limit voltage, wherein the second upper limit voltage is less than a first upper limit voltage, and the first upper limit voltage is the upper limit voltage of charging of the first power supply unit and the second power supply unit when the temperature is less than or equal to a first temperature threshold.

7. The battery pack of claim 6, wherein, A state of charge corresponding to the second upper limit voltage is 90%-99% of a state of charge corresponding to the first upper limit voltage.

8. The battery pack according to any one of claims 4 to 7, characterized by, The response to the temperature being greater than the first temperature threshold, reducing the charging rate and the discharging rate of the first power supply unit and the second power supply unit, further comprises: in response to the temperature being greater than the second temperature threshold and less than or equal to a third temperature threshold, performing the following steps: in response to a 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 hibernation state; in response to a current state of charge of the first power supply unit being greater than the first state of charge threshold, controlling the first power supply unit to discharge, and thereafter, in response to the first power supply unit discharging to a state of charge of the first power supply unit being less than or equal to a second state of charge threshold, controlling the first power supply unit to enter a hibernation state.

9. The battery pack of claim 8, wherein, the first state of charge threshold is 30%, and / or the second state of charge threshold is 0.

10. The battery pack according to claim 8 or 9, characterized by the response to the temperature being greater than the first temperature threshold, reducing a charge rate and a discharge rate of the first power supply unit and the second power supply unit, further comprises: in response to the temperature being greater than a third temperature threshold, controlling the first power supply unit and the second power supply unit to enter a hibernation state.

11. The battery pack of claim 10, wherein, the first temperature threshold is 35°C, and / or the second temperature threshold is 45°C, and / or the third temperature threshold is 60°C.

12. An electrical device, characterized by a battery pack as claimed in any one of claims 1 to 11, and a load.

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