WO2023240599A1 - 一种电池包及其用电装置 - Google Patents

一种电池包及其用电装置 Download PDF

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WO2023240599A1
WO2023240599A1 PCT/CN2022/099470 CN2022099470W WO2023240599A1 WO 2023240599 A1 WO2023240599 A1 WO 2023240599A1 CN 2022099470 W CN2022099470 W CN 2022099470W WO 2023240599 A1 WO2023240599 A1 WO 2023240599A1
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Prior art keywords
battery
battery pack
area
type
battery cell
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PCT/CN2022/099470
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English (en)
French (fr)
Inventor
孙婧轩
刘倩
叶永煌
李全国
徐晓富
吴则利
肖得隽
喻春鹏
Original Assignee
宁德时代新能源科技股份有限公司
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Application filed by 宁德时代新能源科技股份有限公司 filed Critical 宁德时代新能源科技股份有限公司
Priority to EP22946286.6A priority Critical patent/EP4358208A1/en
Priority to CN202280070719.5A priority patent/CN118120085A/zh
Priority to PCT/CN2022/099470 priority patent/WO2023240599A1/zh
Publication of WO2023240599A1 publication Critical patent/WO2023240599A1/zh

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/60—Heating or cooling; Temperature control
    • H01M10/65—Means for temperature control structurally associated with the cells
    • H01M10/653—Means for temperature control structurally associated with the cells characterised by electrically insulating or thermally conductive materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
    • H01M50/20—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders
    • H01M50/204—Racks, modules or packs for multiple batteries or multiple cells
    • H01M50/207—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape
    • H01M50/209—Racks, modules or packs for multiple batteries or multiple cells characterised by their shape adapted for prismatic or rectangular cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/021—Physical characteristics, e.g. porosity, surface area
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries

Definitions

  • the present application relates to the field of secondary batteries, and in particular, to a battery pack and its power device.
  • Secondary batteries have become the most popular energy storage system due to their low cost, long life, and good safety. They are now widely used in pure electric vehicles, hybrid electric vehicles, smart grids and other fields. A battery pack is formed by multiple secondary batteries arranged in a certain space, which can be directly used as the power source of electric vehicles. Secondary batteries are increasingly widely used due to their clean and renewable characteristics. In order to adapt to the needs of different environments and application scenarios, the industry's performance requirements for secondary batteries continue to increase. For example, as the driving energy for new energy vehicles used in different regions around the world, it is necessary to ensure safety performance in high-temperature environments and take into account normal operation in low-temperature and extremely cold regions.
  • a first aspect of the present application provides a battery pack, which includes at least a first type of battery cell and a second type of battery cell.
  • the battery pack includes an A region and a B region, wherein the A region is The area with poor thermal insulation ability is located around and/or at the bottom of the battery pack.
  • the remaining area is area B, where the number of the first battery cells among the battery cells contained in area A accounts for 10% to 100%, and the number of the second battery cells among the battery cells contained in area B is 5% to 100%,
  • the overall safety performance of the battery pack is taken into account while supplementing the shortcomings of low-temperature weak areas.
  • the ion conductivities ⁇ 1 and ⁇ 2 of the electrolyte of the first type of battery cell and the second type of battery cell at -10°C satisfy 0mS/cm ⁇
  • the volumetric energy density D of the two types of battery cells is the same, by limiting the absolute range of the difference in ion conductivity ⁇ between the two, it is possible to match the temperature differences in different regions and improve low-temperature battery life and power. It can also avoid major waste in terms of capacity, performance and cost caused by over-design.
  • the battery pack can have both good low-temperature performance and excellent overall safety performance.
  • the M value when D1 ⁇ D2, the M value satisfies 1.02 ⁇ M2/M1 ⁇ 9; optionally, 1.03 ⁇ M2/M1 ⁇ 8.
  • the viscosities ⁇ 1 and eta2 of the electrolyte of the first type of battery cell and the second type of battery cell at -10°C satisfy 0 ⁇
  • the number of the first battery cells among the battery cells included in the A region is 10% to 100%, optionally 20% to 90%, further optionally 20% to 80%, and the number of the second battery cells among the battery cells contained in the B area is 20% to 100%, optionally 40% to 100%, further optionally is 60% to 100%.
  • different areas in the battery pack have different heat preservation capabilities, and at least two types of areas satisfy the temperature difference ⁇ T in the range of 0 ⁇ T ⁇ 10°C; optionally, 0.1 ⁇ T ⁇ 9°C ; Further optionally, 0.2 ⁇ T ⁇ 8°C.
  • the film-forming impedances of the positive electrode plates in the first type of battery cell and the second type of battery cell are respectively Rct1 and Rct2, which satisfy the relationship: 1 ⁇ Rct1/Rct2 ⁇ 4; optional Ground, 1.01 ⁇ Rct1/Rct2 ⁇ 3.5; further optionally, 1.02 ⁇ Rct1/Rct2 ⁇ 3.
  • Rct is an important parameter in low-temperature discharge usage scenarios. The smaller its value, the better the low-temperature performance. Controlling the Rct ratio within a reasonable range ensures the low-temperature improvement effect while avoiding over-design.
  • the electrolyte of all battery cells in the battery pack has a freezing point ⁇ -20°C, optionally ⁇ -30°C.
  • the volumetric energy density D of the first type of battery cell and the second type of battery cell both satisfies 100Wh/L ⁇ D ⁇ 1000Wh/L; optionally, 200Wh/L ⁇ D ⁇ 900Wh/ L; further optionally, 300Wh/L ⁇ D ⁇ 800Wh/L.
  • the numerical range of the volumetric energy density D of the two types of battery cells can further adjust the low-temperature performance of the battery pack and better match the battery life and power requirements of various application scenarios.
  • a third type of battery cell is also included, which is formed by mixing the main material system of the first type of battery cell and the second type of battery cell, said The third type of battery cell has a volumetric energy density D3, where D3 is between D1 and D2.
  • the battery cells are each independently selected from the group consisting of lithium ion batteries, lithium metal batteries, and sodium ion batteries.
  • the chemical system of the positive active material of the battery cell is independently selected from the group consisting of lithium nickel cobalt manganese, lithium iron phosphate, lithium iron manganese phosphate, lithium iron vanadium phosphate, lithium vanadium phosphate, lithium cobalt oxide, nickel Lithium oxide, lithium-rich manganese, lithium nickel cobalt aluminum and lithium manganate systems, as well as Prussian blue, polyanion, oxide and dual-ion battery systems.
  • the selection of the battery cell system can make the performance of the battery pack more abundant and adjustable.
  • the battery pack includes a first-type battery cells and b second-type battery cells, where a and b are both natural numbers ⁇ 1, and 0.01 ⁇ a/b ⁇ 200; may Optionally, 0.05 ⁇ a/b ⁇ 180; further optionally, 0.1 ⁇ a/b ⁇ 150.
  • the ratio of the numbers of the two types of battery cells can be used to adjust the low-temperature performance and safety performance of the battery pack.
  • a third aspect of the present application provides an electrical device, which includes a battery pack selected from the first aspect of the present application and/or a battery pack of the second aspect.
  • Figure 1 is a schematic diagram of a lithium ion secondary battery in one embodiment of the present application.
  • FIG. 2 is an exploded view of the lithium ion secondary battery in one embodiment of the present application shown in FIG. 1 .
  • Figure 3 is a schematic diagram of a battery pack in an embodiment of the present application.
  • FIG. 4 is an exploded view of the battery pack in one embodiment of the present application shown in FIG. 3 .
  • FIG. 5 is a schematic diagram of the area division and battery cell arrangement of the battery pack in one embodiment of the present application shown in FIG. 3 .
  • Figure 6 is a schematic diagram of a device in which a battery pack is used as a power source in an embodiment of the present application.
  • any lower limit can be combined with any upper limit to form an unexpressed range; and any lower limit can be combined with other lower limits to form an unexpressed range, and likewise any upper limit can be combined with any other upper limit to form an unexpressed range.
  • each individually disclosed point or single value may itself serve as a lower or upper limit in combination with any other point or single value or with other lower or upper limits to form a range not expressly recited.
  • the first aspect of this application provides a battery pack, which includes at least a first type of battery cell and a second type of battery cell.
  • the battery pack includes an A region and a B region, where the A region has a thermal insulation capability.
  • the poorer area is located around and/or at the bottom of the battery pack, and the remaining area is area B, where the number of the first battery cells among the battery cells contained in area A accounts for 10% to 100%.
  • the proportion of the second battery cells among the battery cells contained in area B is 5% to 100%
  • the volumetric energy density D of the two types of battery cells contained therein is the same, that is, the cathode, anode, separator and other main materials used by the two types of battery cells and their The proportions are the same.
  • the low-temperature conductivity ⁇ of the battery's electrolyte is changed, so that the battery cells placed in the weak insulation area of the battery pack have higher low-temperature discharge capabilities without deteriorating the safety performance of the battery pack.
  • the low-temperature conductivity difference is controlled within a reasonable range to avoid large waste in terms of capacity, performance, cost, etc., so as to supplement the battery life and power shortcomings in low-temperature weak areas, while taking into account the overall battery pack Technical effects of safety performance.
  • volumetric energy density D of the two types of battery cells included When the volumetric energy density D of the two types of battery cells included is different, it means that the main material systems or main material components used by the two types of battery cells are different. According to experience in lithium-ion battery systems, batteries with higher volumetric energy density D usually have relatively poor safety performance. Because the volume energy density D affects the intensity of the battery's thermal runaway and the speed of heat radiation to the surroundings, it is usually inversely proportional to the safety performance, that is, the larger 1/D, the safer it is. At the same time, low-temperature discharge capabilities of systems with high energy density tend to be more advantageous, so the low-temperature conductivity requirements of the electrolyte systems usually used are relatively low.
  • the system with a smaller K value is more suitable for placement in areas with weak thermal insulation.
  • the K value ratio it not only supplements the shortcomings of the low-temperature weak area but also ensures that the overall battery pack has high safety performance.
  • the K value when D1 ⁇ D2, the K value satisfies 1.02 ⁇ K2/K1 ⁇ 5; optionally, 1.03 ⁇ K2/K1 ⁇ 3.
  • the volume energy density D of a battery cell is mainly related to the cathode, anode, separator and other main materials of the battery cell and their proportions. Therefore, the volume energy density D can be adjusted by selecting specific main materials and their proportions.
  • the ionic conductivity ⁇ of the electrolyte of the battery cell at -10°C can be directly measured at the corresponding temperature using a conductivity meter. For the battery cells of a given system, the ionic conductivity ⁇ of the electrolyte can be adjusted by selecting the specific ionic species of the electrolyte and the types and proportions of solvents, co-solvents and additives.
  • the ionic conductivities ⁇ 1 and ⁇ 2 of the electrolyte of the first type of battery cell and the second type of battery cell at -10°C satisfy 0 ⁇
  • the volumetric energy density D of the two types of battery cells is the same, by limiting the absolute value range of the difference in ionic conductivity ⁇ between the two types of battery cells, the balance between the low-temperature performance and the safety performance of the battery pack can be advantageously adjusted.
  • the electrolyte has an ionic conductivity ⁇ limited to a total range of 0.5-15 mS/cm, optionally 1-10 mS/cm at -10°C.
  • a second aspect of the present application provides another battery pack, which includes at least a first type of battery cell and a second type of battery cell.
  • the battery pack includes an A region and a B region, wherein the A region has poor thermal insulation ability.
  • area, located around and/or at the bottom of the battery pack, the remaining area is area B, where the number of the first battery cells among the battery cells contained in area A accounts for 10% to 100%, and The quantity proportion of the second battery cells among the battery cells contained in area B is 5% to 100%,
  • the volumetric energy density of the two types of battery cells contained therein when the volumetric energy density of the two types of battery cells contained therein is the same, it means that the main materials such as cathodes, anodes, and separators used in the two types of batteries and their proportions are the same. At this time, only the low-temperature viscosity of the electrolyte of these two types of battery cells is changed, so that the battery cells placed in the weak insulation area of the battery pack have higher low-temperature discharge capabilities without deteriorating the safety performance of the battery pack.
  • the low-temperature viscosity ratio is controlled within a more reasonable range to avoid large waste in terms of capacity, performance, cost, etc., so as to supplement the battery life and power shortcomings in low-temperature weak areas while taking into account the overall safety performance of the battery pack. technical effects.
  • volume energy densities of the two types of battery cells are different, it means that the main material systems or main material components used in the two types of batteries are different.
  • batteries with higher volumetric energy density D usually have relatively poor safety performance.
  • the volume energy density D affects the severity of the battery's thermal runaway and the speed of heat radiation to the surroundings, it is usually inversely proportional to the safety performance, that is, the larger 1/D, the safer it is.
  • low-temperature discharge capabilities of systems with high energy density tend to be more advantageous, so the electrolyte system usually used with them has relatively low demand for reducing viscosity at low temperatures.
  • M the more suitable the system is to be placed in areas with weak thermal insulation.
  • M value ratio it not only supplements the shortcomings of the low-temperature weak area, but also ensures that the overall battery pack has high safety performance.
  • the M value when D1 ⁇ D2, the M value satisfies 1.02 ⁇ M2/M1 ⁇ 9; optionally, 1.03 ⁇ M2/M1 ⁇ 8.
  • the viscosities ⁇ 1 and eta2 of the electrolyte of the first type of battery cell and the second type of battery cell at -10°C satisfy 0 ⁇
  • the viscosity eta of the electrolyte is limited to a total range of 3-20 mPa s, optionally 5-15 mPa s at -10°C.
  • the first battery cells account for 10% to 90% of the battery cells included in the A region, optionally 20% to 90%, and further optionally 20% to 80%, and the number of the second battery cells among the battery cells contained in the B area is 20% to 100%, optionally 40% to 100%, further optionally is 60% to 100%.
  • the quantity ratio of the first battery cell and the second battery cell in area A and area B can be adjusted according to the K value and M value of each battery cell.
  • the diagonal length and width of the battery pack in the horizontal direction is Lc, and the two diagonal lines are connected to four points at 1/5Lc equal points from the end points.
  • the area is defined as area B, and the remaining area is defined as area A. Since the thus formed area A is located at the relative periphery of the battery pack, its heat preservation capability is poorer than that of the inner area. When the battery pack operates at low temperatures, the battery cells in its A area need to have relatively stronger low-temperature discharge capabilities. However, since area A is located on the periphery, its safety is also poor. Therefore, the low-temperature discharge capability and safety performance of the battery cells need to be overall planned to achieve a balance. Correspondingly, area B is relatively internal, has better thermal insulation capabilities, and is also safer. The division of area A and area B in the horizontal direction reasonably defines the spatial distribution of the two battery cells with different properties.
  • the vertical height of the battery pack is defined as Ld
  • the area below the bottom 1/5 Ld is defined as area A
  • the remaining area above The area of 4/5Ld is defined as area B.
  • the battery pack has a cuboid structure, which is rectangular in a horizontal plane, with a length La, a width Lb, a diagonal length Lc, and a vertical height Ld.
  • different areas in the battery pack have different heat preservation capabilities, and at least two types of areas satisfy the temperature difference ⁇ T in the range of 0 ⁇ T ⁇ 10°C; optionally, 0.1 ⁇ T ⁇ 9 °C; further optionally, 0.2 ⁇ T ⁇ 8°C.
  • the temperature difference range of at least two areas in the battery pack it is helpful to achieve the effect of differentiated arrangement and at the same time improve the uniformity of the temperature of the battery pack. Only when there are at least two types of areas in the battery pack with a temperature difference ⁇ T greater than 0°C can a temperature gradient be formed so that battery cells with different properties can achieve balance; and when the temperature difference ⁇ T is too large, the temperature difference ⁇ T will Making balancing within the battery pack difficult.
  • the film-forming impedances of the positive electrode plates in the first type of battery cell and the second type of battery cell are respectively Rct1 and Rct2, which satisfy the relationship: 1 ⁇ Rct1/Rct2 ⁇ 4; optional Ground, 1.01 ⁇ Rct1/Rct2 ⁇ 3.5; further optionally, 1.02 ⁇ Rct1/Rct2 ⁇ 3.
  • the ratio range of the film-forming impedances of the two types of battery cells can further differentiate the discharge capabilities of the two types of battery cells and help improve the performance balance of the battery pack.
  • the film-forming impedance reflects the discharge capability of the battery cell, and the ratio between the two must be within a reasonable range so that the spatial arrangement of different battery cells can be adjusted to achieve a precise balance.
  • Rct is an important parameter in low-temperature discharge usage scenarios. The smaller its value, the better the low-temperature performance. Controlling the Rct ratio within a reasonable range ensures the low-temperature improvement effect while avoiding over-design.
  • the electrolyte of all battery cells in the battery pack has a freezing point ⁇ -20°C, optionally ⁇ -30°C. Setting the freezing point of the electrolyte of the battery cell within this range can ensure that the battery pack has good discharge capability at low temperatures. When the freezing point is too high, when the battery pack is operated at low temperature for a long time, the ion migration ability in the electrolyte will be seriously reduced, which is not conducive to the low-temperature performance. By setting the upper limit of the freezing point of the electrolyte of the battery cell, it can be ensured that the battery pack has good discharge capability at low temperatures. The lower the freezing point, the wider the window for low-temperature applications.
  • the volumetric energy density D of the first type of battery cell and the second type of battery cell both satisfies 100Wh/L ⁇ D ⁇ 1000Wh/L; optionally, 200Wh/L ⁇ D ⁇ 900Wh/ L; further optionally, 300Wh/L ⁇ D ⁇ 800Wh/L.
  • the numerical range of the volumetric energy density D of the two types of battery cells can further realize the adjustment of the low-temperature performance of the battery pack.
  • choosing a material system with an appropriate energy density range can make it have good practical application value and product competitiveness, so as to better match the battery life and power requirements of various application scenarios.
  • a third type of battery cell is also included, which is formed by mixing the main material system of the first type of battery cell and the second type of battery cell, said The third type of battery cell has a volumetric energy density D3, where D3 is between D1 and D2.
  • the low-temperature performance and overall safety performance of the battery pack can be more accurately controlled and adjusted, making it easier to achieve a balance.
  • the setting of the third type of battery cells can expand the performance adjustment range of the battery pack, so that the selection of battery cells is not limited to battery combinations of different pure systems, but also covers combinations between various blended systems and pure systems.
  • the battery cells are each independently selected from the group consisting of lithium ion batteries, lithium metal batteries, and sodium ion batteries.
  • the chemical system of the positive active material of the battery cell is independently selected from the group consisting of lithium nickel cobalt manganese, lithium iron phosphate, lithium iron manganese phosphate, lithium iron vanadium phosphate, lithium vanadium phosphate, lithium cobalt oxide, nickel Lithium oxide, lithium-rich manganese, lithium nickel cobalt aluminum and lithium manganate systems, as well as Prussian blue, polyanion, oxide and dual-ion battery systems.
  • the selection of the battery cell system can make the performance of the battery pack more abundant and adjustable.
  • the battery pack includes a first-type battery cells and b second-type battery cells, where a and b are both natural numbers ⁇ 1, and 0.01 ⁇ a/b ⁇ 200; may Optionally, 0.05 ⁇ a/b ⁇ 180; further optionally, 0.1 ⁇ a/b ⁇ 150.
  • the ratio of the number of the two types of battery cells is controlled within a reasonable range, which can effectively adjust the low-temperature performance and safety performance of the battery pack.
  • both the first type of battery cells and the second type of battery cells are lithium ion secondary batteries.
  • the battery cells can also be selected from other systems, such as sodium-ion batteries.
  • a lithium-ion secondary battery typically includes a positive electrode plate, a negative electrode plate, a separator and an electrolyte.
  • active ions are inserted and detached back and forth between the positive and negative electrodes.
  • the isolation film is arranged between the positive electrode piece and the negative electrode piece to play the role of isolation.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the electrolyte plays a role in conducting ions between the positive and negative electrodes.
  • the electrolyte includes electrolyte salts and solvents.
  • the electrolyte salt can be a commonly used electrolyte salt in lithium ion secondary batteries, such as lithium salt, including the above-mentioned lithium salt as a high thermal stability salt, a lithium salt as a low resistance additive, or lithium that inhibits aluminum foil corrosion. Salt.
  • the electrolyte salt may be selected from lithium hexafluorophosphate (LiPF 6 ), lithium tetrafluoroborate (LiBF 4 ), lithium hexafluoroarsenate (LiAsF 6 ), lithium bisfluorosulfonyl imide (LiFSI), bistrifluoromethanesulfonyl Lithium imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluoromethanesulfonate borate (LiDFOB), lithium difluorophosphate (LiPO 2 F 2 ), lithium difluorodioxalate phosphate (LiDFOP), fluorosulfonic acid Lithium (LiSO 3 F), difluorodioxalate (NDFOP), Li 2 F(SO 2 N) 2 SO 2 F, KFSI, CsFSI, Ba(FSI) 2 and LiFSO 2 NSO 2 CH 2 CH 2 CH 2 CH 2
  • the solvent is a non-aqueous solvent.
  • the solvent may include one or more of chain carbonate, cyclic carbonate, and carboxylic acid ester.
  • the solvent may be selected from ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), Dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methyl formate (MF), methyl acetate Ester (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB) , one of ethyl
  • additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain properties of the battery, such as additives that improve battery overcharge performance, additives that improve battery high-temperature performance, and battery low-temperature performance. additives, etc.
  • the additive is selected from the group consisting of cyclic carbonate compounds containing unsaturated bonds, halogen-substituted cyclic carbonate compounds, sulfate compounds, sulfite compounds, sultone compounds, disulfonic acid compounds, and nitrile compounds.
  • the positive electrode sheet includes a positive electrode current collector and a positive electrode material layer disposed on at least one surface of the positive electrode current collector.
  • the positive electrode material layer includes a positive electrode active material and carbon.
  • the positive electrode current collector has two surfaces opposite in its own thickness direction, and the positive electrode material layer is disposed on any one or both of the two opposite surfaces of the positive electrode current collector.
  • the positive electrode current collector can be a metal foil or a composite current collector.
  • the metal foil aluminum foil can be used.
  • the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer.
  • the composite current collector can be formed by forming metal materials (such as aluminum, aluminum alloys, nickel, nickel alloys, titanium, titanium alloys, silver and silver alloys, etc.) on polymer material substrates (such as polypropylene (PP), polyterephthalene). Formed on substrates such as ethylene formate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).
  • the cathode material layer disposed on the surface of the cathode current collector includes a cathode active material.
  • the cathode active material used in the present application may have a structure of Formula (I), Formula (II), Formula (III) or Formula (IV) as described above and various numerical definitions defined therein.
  • the cathode active material of formula (I), formula (II), formula (III) or formula (IV) accounts for 60-100% of the total weight of the cathode active material of the battery cell in each case. % by weight, optionally 80-100% by weight.
  • the positive electrode active material may also include one or more other materials selected from the group consisting of lithium transition metal oxides, lithium-containing phosphates with an olivine structure, and their respective modified compounds. kind.
  • lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide One or more of lithium nickel cobalt aluminum oxide and its modified compounds.
  • the cathode material layer optionally also includes a binder.
  • the binder may be styrene-butadiene rubber (SBR), water-based acrylic resin, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), ethylene-vinyl acetate copolymer (EVA), polyacrylic acid ( One or more of PAA), carboxymethyl cellulose (CMC), polyvinyl alcohol (PVA) and polyvinyl butyral (PVB).
  • SBR styrene-butadiene rubber
  • PVDF polyvinylidene fluoride
  • PTFE polytetrafluoroethylene
  • EVA ethylene-vinyl acetate copolymer
  • PAA polyacrylic acid
  • CMC carboxymethyl cellulose
  • PVA polyvinyl alcohol
  • PVB polyvinyl butyral
  • the specific type of the negative active material is not limited. Active materials known in the art that can be used for the negative electrode of lithium ion secondary batteries can be used. Those skilled in the art can make a selection according to actual needs.
  • the negative active material may be selected from one or more of graphite, soft carbon, hard carbon, mesocarbon microspheres, carbon fibers, carbon nanotubes, elemental silicon, silicon oxide compounds, silicon carbon composites, and lithium titanate. kind.
  • the conductive agent may be selected from one or more types of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene and carbon nanofibers.
  • the binder may be selected from styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), One or more of polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).
  • SBR styrene-butadiene rubber
  • PAA polyacrylic acid
  • PAAS sodium polyacrylate
  • PAM polyacrylamide
  • PVA polyvinyl alcohol
  • SA sodium alginate
  • PMAA polymethacrylic acid
  • CMCS carboxymethyl chitosan
  • the positive electrode piece, the negative electrode piece and the separator film can be made into an electrode assembly through a winding process or a lamination process.
  • the lithium ion secondary battery may include an outer packaging.
  • the outer packaging can be used to package the above-mentioned electrode assembly and electrolyte.
  • the outer package may include a housing 51 and a cover 53 .
  • the housing 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity.
  • the housing 51 has an opening communicating with the accommodation cavity, and the cover plate 53 can cover the opening to close the accommodation cavity.
  • the positive electrode piece, the negative electrode piece and the isolation film can be formed into the electrode assembly 52 through a winding process or a lamination process.
  • the electrode assembly 52 is packaged in the containing cavity.
  • the electrolyte soaks into the electrode assembly 52 .
  • the number of electrode assemblies 52 contained in the lithium ion secondary battery 5 can be one or more, and those skilled in the art can select according to specific actual needs.
  • the battery pack 1 may include a battery box and a plurality of battery cells arranged in the battery box.
  • the battery box includes an upper box 2 and a lower box 3.
  • the upper box 2 can be covered with the lower box 3 and form a closed space for accommodating battery cells.
  • FIG 5 is a schematic diagram of the regional division of the battery pack and the arrangement of battery cells in one embodiment of the present application.
  • the battery pack has a length La in the horizontal direction, a width Lb, and a diagonal line Lc. The distance between the two diagonal lines Lc is 1/5 Lc from the end points. The area enclosed by four connected points is defined as area B, and the remaining area is defined as area A.
  • the vertical height of the battery pack is defined as Ld
  • the area below the bottom 1/5Ld is defined as area A
  • the area 4/5Ld above the remaining area is defined as area B.
  • the battery cells are placed in corresponding areas according to the types and quantity ratios described in this application, thereby realizing the adjustment of discharge performance in different areas.
  • -20°C discharge capacity test Place the battery pack in a -20°C environment, discharge the lithium-ion battery at a fixed rate of 1/3C1, discharge to the lower limit voltage, and record the discharge capacity at this time as C2;
  • Positive electrode plate Dissolve the positive active material LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in the solvent N- in a weight ratio of 90:5:5. In methylpyrrolidone (NMP), stir and mix thoroughly to obtain a positive electrode slurry; then the positive electrode slurry is evenly coated on the positive electrode current collector, and then dried, cold pressed, and cut to obtain positive electrode sheets.
  • NMP methylpyrrolidone
  • Negative electrode plate Dissolve the active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC) in a weight ratio of 90:4:4:2.
  • the negative electrode slurry is prepared by uniformly mixing the solvent deionized water with the solvent deionized water; then the negative electrode slurry is evenly coated on the negative electrode current collector copper foil one or more times, dried to obtain the negative electrode diaphragm, and then cold pressed , slit to obtain the negative electrode piece.
  • Electrolyte In an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm), mix the organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). ) are uniformly mixed according to the weight ratios listed in Table 1 and Table 2 respectively, add lithium hexafluorophosphate (LiPF 6 ) and adjust to a concentration of 1M/L, stir evenly, and obtain the corresponding electrolyte.
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • Battery preparation Use the positive electrode piece and negative electrode piece prepared as above, use polypropylene film as the isolation film, stack the positive electrode piece, isolation film, and negative electrode piece in order, so that the isolation film is at the positive and negative electrodes.
  • the sheets play a role in isolating each other, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the battery case, dried and then injected with electrolyte, and then formed and left to stand to prepare a lithium-ion secondary battery as a battery cell.
  • Positive electrode sheet Dissolve the lithium iron manganese phosphate LiMn 0.6 Fe 0.4 PO 4 (LMFP) as the positive active material, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) in a weight ratio of 96:2:2. In the solvent N-methylpyrrolidone (NMP), stir thoroughly and mix evenly to obtain a positive electrode slurry.
  • NMP N-methylpyrrolidone
  • use a particle screening machine to screen the selected lithium iron phosphate granular materials and lithium iron manganese phosphate granular materials, and further screen various materials into fractions with different volume average particle diameter D50 values, and apply them to different Battery cells are being prepared.
  • the positive electrode slurry is evenly coated on the aluminum positive electrode current collector, and then dried, cold pressed, and cut to obtain positive electrode sheets.
  • Negative electrode sheet Combine the negative active material artificial graphite, conductive agent acetylene black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethylcellulose (CMC-Na) in a weight ratio of 95:2:2: 1 Dissolve in the solvent deionized water, mix evenly and prepare negative electrode slurry.
  • the negative electrode slurry is evenly coated on the negative electrode current collector copper foil, and after drying, it is cold pressed and cut to obtain negative electrode sheets.
  • Electrolyte In an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm), mix the organic solvents ethylene carbonate (EC), dimethyl carbonate (DMC) and ethyl methyl carbonate (EMC). ) are uniformly mixed according to the weight ratios listed in Table 1 and Table 2 respectively, add lithium hexafluorophosphate (LiPF 6 ) and adjust to a concentration of 1M/L, stir evenly, and obtain the corresponding electrolyte.
  • EC ethylene carbonate
  • DMC dimethyl carbonate
  • EMC ethyl methyl carbonate
  • Battery preparation Use the positive electrode piece and negative electrode piece prepared as above, use polypropylene film as the isolation film, stack the positive electrode piece, isolation film, and negative electrode piece in order, so that the isolation film is at the positive and negative electrodes.
  • the sheets play a role in isolating each other, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the battery case, dried and then injected with electrolyte, and then formed and left to stand to prepare a lithium-ion secondary battery as a battery cell.
  • Electrolyte In an argon atmosphere glove box (H 2 O ⁇ 0.1ppm, O 2 ⁇ 0.1ppm), mix the organic solvent EC/EMC evenly according to the volume ratio of 3/7, add 12.5% LiPF 6 lithium salt and dissolve it in the organic solvent. In the solvent, stir evenly to obtain the corresponding electrolyte.
  • Battery preparation Use the positive electrode piece and negative electrode piece prepared as above, use polypropylene film as the isolation film, stack the positive electrode piece, isolation film, and negative electrode piece in order, so that the isolation film is at the positive and negative electrodes.
  • the sheets play a role in isolating each other, and then the electrode assembly is obtained by winding.
  • the electrode assembly is placed in the battery case, dried and then injected into the electrolyte, and then formed and left to stand to prepare a lithium ion secondary battery as a battery cell.
  • each battery pack contains only two types of battery cells prepared as described above, respectively labeled as first type battery cells and second type batteries.
  • area A is the area surrounded by four points connected to the horizontal length and width diagonal Lc of the battery pack at 1/5Lc equal points from the end points, and located 1/5 from the bottom
  • area B The area below the vertical height Ld and the rest of the battery pack are area B.
  • the number of all battery cells contained in area A is 48, of which the number of first-type battery cells is 40 and the number of second-type battery cells is 8; the number of all battery cells included in area B is The number is 72, of which the number of first-type battery cells is 27 and the number of second-type battery cells is 45.
  • the value of K2/K1 or M2/M1 greater than 1 will bring about a relatively high capacity retention rate, while evenly Meet the requirements for heat spread barrier, as shown in Examples 2-6.
  • the capacity retention rate is related to the specific battery system used, and does not change in proportion to its K2/K1 or M2/M1 values.
  • the value of K2/K1 or M2/M1 in the hybrid system is less than 1, the capacity retention rate of the battery pack is reduced and the battery pack cannot pass the thermal spread barrier test (Comparative Example 3).

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Abstract

本申请涉及一种电池包，其包括至少第一类电池单体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且B区域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的离子电导率σ分别为σ1和σ2，定义K＝D 2×σ，则K1＝D1 2×σ1且K2＝D2 2×σ2，其中：当D1＝D2时，K值满足0.2<K2/K1≤0.99；并且当D1≠D2时，K值满足1.01≤K2/K1≤10。本申请还涉及包含所述电池包的用电装置。

Description

一种电池包及其用电装置 技术领域
本申请涉及二次电池领域，尤其涉及一种电池包及其用电装置。
背景技术
二次电池因其成本低、寿命长，安全性好等特点成为最受欢迎的能量存储系统，现已被广泛应用于纯电动汽车、混合电动汽车以及智能电网等领域。由多个二次电池通过一定的空间排布形成电池包，可直接作为电动汽车的动力来源。二次电池因其清洁和可再生的特点得到日益广泛的应用，而为了适应不同环境和应用场景需要，业内对二次电池的性能要求不断提高。例如，作为新能源汽车的驱动能源在全球不同地区使用，既要保证高温环境下的安全性能，又要兼顾低温极寒地区的正常运行。锂离子电池由于在低温下极化很大导致放电会提前到达截止电压、放电能量减小以及功率减小。因此，低温性能作为常用锂离子电池的固有瓶颈，长久以来难以实现突破。
现有技术中主要通过在电池包中包括两种耐寒能力有差异的电池单体来解决这一问题，然而，现有技术中的这些技术方案虽然提升了整包的低温放电能力，但对于不同类型化学体系的电池其安全性能有较大差异。因此，目前在二次电池领域仍然存在对于兼顾低温放电能力和整体安全性能的电池包以及用电装置的需求。
发明内容
本申请是鉴于上述课题而进行的，其目的在于提供一种电池包，以解 决低温放电能力与整体安全性能无法兼顾的技术问题。
为了达到上述目的，本申请第一方面提供一种电池包，其包括至少第一类电池单体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且B区域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，
其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的离子电导率σ分别为σ1和σ2，定义K＝D 2×σ，则K1＝D1 2×σ1且K2＝D2 2×σ2，其中：
当D1＝D2时，K值满足0.2<K2/K1≤0.99；并且
当D1≠D2时，K值满足1.01≤K2/K1≤10。
通过将具有相同或不同的体积能量密度D以及电解液离子电导率σ的电池进行搭配和差异化排布，在补充低温薄弱区短板的同时兼顾了电池包的整体安全性能。
在任意实施方案中，当D1＝D2时，K值满足0.25≤K2/K1≤0.98；可选地，0.3≤K2/K1≤0.96。当D1≠D2时，K值满足1.02≤K2/K1≤5；可选地，1.03≤K2/K1≤3。通过设定两类电池单体的体积能量密度D相同以及不同的情况，进一步选择K值比例的优选范围，可以持续改善电池包整体的低温性能和安全性能的平衡。
在任意实施方案中，当D1＝D2时，所述第一类电池单体和第二类电池单体的电解液在-10℃下的离子电导率σ1和σ2满足0mS/cm<|σ1-σ2|<8mS/cm；可选地，0.05mS/cm<|σ1-σ2|<7mS/cm；进一步可选地，0.1mS/cm<|σ1-σ2|<6mS/cm。在所述两类电池单体的体积能量密度D相同时，通过限定二者的离子电导率σ的差值的绝对值范围，既可以匹配不 同区域温度差异并发挥改善低温续航和功率的效果，也可以避免过设计导致的容量发挥、性能以及成本等方面的较大浪费。
本申请第二方面提供另外一种电池包，其包括至少第一类电池单体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且B区域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，
其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的粘度η分别为η1和η2，定义M＝D/η，则M1＝D1/η1且M2＝D2/η2，其中：
当D1＝D2时，M值满足0.2<M2/M1≤0.99；并且
当D1≠D2时，M值满足1.01≤M2/M1≤10。
通过将具有相同或不同的体积能量密度D以及电解液粘度η的电池进行搭配和差异化排布，所述电池包可以兼具良好的低温性能以及同时优异的整体安全性能。
在任意实施方案中，当D1＝D2时，M值满足0.25≤M2/M1≤0.98；可选地，0.3≤M2/M1≤0.96。当D1≠D2时，M值满足1.02≤M2/M1≤9；可选地，1.03≤M2/M1≤8。通过假定两种电池单体的体积能量密度D相同或不同的情况，进一步优选二者M值的比例，可实现对于所述电池包的低温性能以及整体安全性能的最佳平衡。
在任意实施方案中，当D1＝D2时，所述第一类电池单体和第二类电池单体的电解液在-10℃下的粘度η1和η2满足0<|η2-η1|<5mPa·s；可选地，0.05mPa·s<|η2-η1|<4mPa·s；进一步可选地，0.1mPa·s<|η2-η1|<3mPa·s。通过设定两种电池单体的粘度η的差值的绝对值，可以方便 地调节所述电池包在低温性能以及整体安全性能的平衡状况，同时避免过设计导致的容量发挥/性能/成本等方面的较大浪费。
在任意实施方案中，所述A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，可选地为20％至90％，进一步可选地为20％至80％，并且所述B区域所包含的电池单体中所述第二电池单体的数量占比为20％至100％，可选地为40％至100％，进一步可选地为60％至100％。
在任意实施方案中，所述电池包在水平方向上的长宽对角线为Lc，在两条所述对角线距离端点各自1/5Lc等分点处的四个点相连所围成的区域定义为B区域，剩余区域定义为A区域。在一些实施方案中，当所述电池包中的电池单元为多层重叠放置时，将所述电池包的垂直高度定义为Ld，位于底部1/5Ld处以下的区域定义为A区域，剩余上方4/5Ld的区域定义为B区域。通过对所述电池包在水平方向以及垂直方向上进行空间划分，可以合理地界定保温能力较差的区域以及保温能力相对较好的区域，并相应地设置具有不同性能的电池单体，从而实现对于电池包低温性能以及整体安全性能的平衡。
在任意实施方案中，所述电池包中不同区域具有不同的保温能力，且至少有两类区域满足温度差值ΔT的范围为0<ΔT<10℃；可选地，0.1<ΔT<9℃；进一步可选地，0.2<ΔT<8℃。通过设定所述电池包中至少两个区域的温度差值的范围，有助于差异化排布的效果体现，同时提升电池包温度的均一性。
在任意实施方案中，所述第一类电池单体和第二类电池单体中正极极片的成膜阻抗分别为Rct1和Rct2，二者满足关系：1≤Rct1/Rct2≤4；可选地，1.01≤Rct1/Rct2≤3.5；进一步可选地，1.02≤Rct1/Rct2≤3。Rct作为低温放电的使用场景中重要的参数，其值越小，低温性能越好。将Rct 比值控制在合理的范围内，保证了低温改善效果同时避免过设计。
在任意实施方案中，所述电池包中的所有电池单体的电解液的凝固点≤-20℃，可选地≤-30℃。通过设定所述电池单体的电解液的凝固点的上限值，可确保所述电池包在低温下具有良好的放电能力，凝固点越低，则低温应用的窗口越宽。
在任意实施方案中，所述第一类电池单体和第二类电池单体的体积能量密度D均满足100Wh/L<D<1000Wh/L；可选地，200Wh/L<D<900Wh/L；进一步可选地，300Wh/L<D<800Wh/L。所述两类电池单体的体积能量密度D的数值范围可进一步实现对于所述电池包的低温性能的调节，更好地匹配各类应用场景的续航和功率需求。
在任意实施方案中，当D1≠D2时，还包含第三类电池单体，其为使用第一类电池单体和第二类类电池单体的主材料体系进行物混而形成，所述第三类电池单体具有体积能量密度D3，其中D3介于D1和D2之间。在一些实施方案中，所述第三类电池单体的电解液在-10℃下的离子电导率σ为σ3，定义K3＝D3 2×σ3，K3介于K1与K2之间；或者所述第三类电池单体的电解液在-10℃下的粘度η为η3，定义M3＝D3/η3，M3介于M1与M2之间。通过在上述两类电池单体以外再设置第三类或者其他的电池单体，可更加精确地控制和调节所述电池包的低温性能和整体安全性能，使其更容易达到平衡。
在任意实施方案中，所述电池单体分别独立地选自锂离子电池、锂金属电池以及钠离子电池。在一些实施方案中，所述电池单体的正极活性材料的化学体系独立地选自锂镍钴锰、磷酸铁锂、磷酸锰铁锂、磷酸钒铁锂、磷酸钒锂、钴酸锂、镍酸锂、富锂锰、锂镍钴铝和锰酸锂体系，以及普鲁士蓝类、聚阴离子类、氧化物类、双离子电池体系。所述电池单体的体系的选择可使得电池包的性能更加丰富和可调。
在任意实施方案中，所述电池包包含a个第一类电池单体和b个第二类电池单体，其中a和b均为≥1的自然数，并且0.01＜a/b≤200；可选地，0.05≤a/b≤180；进一步可选地0.1≤a/b≤150。所述两类电池单体的数量之比可用于调节所述电池包的低温性能和安全性能。
本申请的第三方面提供一种用电装置，其包括选自本申请的第一方面的电池包和/或第二方面的电池包。
附图说明
为了更清楚地说明本申请的技术方案，下面将对本申请实施例中所需要使用的附图作简单的介绍。显而易见地，下面所描述的附图仅仅是本申请的一些实施例，对于本领域普通技术人员来讲，在不付出创造性劳动的前提下，还可以根据附图获得其他的附图。
图1是本申请一个实施方式中的锂离子二次电池的示意图。
图2是图1所示的本申请一个实施方式中的锂离子二次电池的分解图。
图3是本申请一个实施方式中的电池包的示意图。
图4是图3所示的本申请一个实施方式中的电池包的分解图。
图5是图3所示的本申请一个实施方式中的电池包的区域划分以及电池单体排布的示意图。
图6是本申请一个实施方式中的电池包用作电源的装置的示意图。
附图标记说明
1 电池包
2 上箱体
3 下箱体
4 电池模块
5 锂离子二次电池
51 壳体
52 电极组件
53 盖板
具体实施方式
为了简明，本申请具体地公开了一些数值范围。然而，任意下限可以与任意上限组合形成未明确记载的范围；以及任意下限可以与其它下限组合形成未明确记载的范围，同样任意上限可以与任意其它上限组合形成未明确记载的范围。此外，每个单独公开的点或单个数值自身可以作为下限或上限与任意其它点或单个数值组合或与其它下限或上限组合形成未明确记载的范围。
现有技术中通过在电池包的不同区域放置具有不同低温放电能力的电池单体来改善其低温性能，但是这种解决方案在电池包的整体安全性能方面存在实质的风险问题。仅通过放电能力来区分不同种类的电池单体，会导致放电性能高但是安全性能较差的电池单体放置在电池包的外围，而电池包的外围区域在挤压碰撞、高温加热、跌落等情况下更容易产生热失控的风险。如此，则面临在风险高的区域恰好放置的是安全性能较差的电池单体，从而导致由此构建的电池包无法兼顾低温放电性能和整体安全性能的问题。
本发明人发现，可以通过对电池包中不同种类的电池单体的特定参数进行选择和设定，使其处于特定范围内，可实现对于电池包的低温放电性能和整体安全性能的有效平衡。
具体的，本申请第一方面提供一种电池包，其包括至少第一类电池单 体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且B区域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，
其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的离子电导率σ分别为σ1和σ2，定义K＝D 2×σ，则K1＝D1 2×σ1且K2＝D2 2×σ2，其中：
当D1＝D2时，K值满足0.2<K2/K1≤0.99；并且
当D1≠D2时，K值满足1.01≤K2/K1≤10。
对于上述本申请第一方面限定的电池包，当其中包含的两类电池单体的体积能量密度D相同时，即表现为这两类电池单体使用的阴极、阳极、隔膜等主材料及其比例相同。此时仅改变电池的电解液的低温电导率σ，使电池包的保温薄弱区域放置的电池单体具有更高的低温放电能力，同时不恶化电池包的安全性能。另外，将低温电导率差值控制在较为合理的范围内，避免容量发挥、性能、成本等方面的较大浪费，从而达到补充低温薄弱区续航以及功率短板的同时，兼顾了电池包的整体安全性能的技术效果。
当其中包含的两类电池单体的体积能量密度D不同时，即表现为这两类电池单体使用的主材料体系或主材料成分占比不同。按照锂离子电池体系中的经验，体积能量密度D更高的电池，通常其安全性能相对较差。因为体积能量密度D影响电池热失控后的剧烈程度以及向周围热辐射的速度，通常其与安全性能成反比，即1/D越大越安全。同时，高能量密度的体系低温放电能力往往更有优势，因此通常搭配使用的电解液体系的低温电导率需求相对较低。基于以上规律，电池包中使用锂离子电池中不同体 系电池的搭配，K值越小的体系，越适合放在保温薄弱区域。通过K值比例的范围限定，补充低温薄弱区短板的同时又保证了电池包的整体具有较高的安全性能。
总的来说，通过选择这两类电池单体的体积能量密度D以及其电解液在低温下的离子电导率σ，并将其乘积K＝D 2×σ设定在合适的范围内，可实现对于所述电池包的低温放电能力以及整体安全性能的最佳平衡。
在一些实施方案中，当D1＝D2时，K值满足0.25≤K2/K1≤0.98；可选地，0.3≤K2/K1≤0.96。当D1≠D2时，K值满足1.02≤K2/K1≤5；可选地，1.03≤K2/K1≤3。通过设定两类电池单体的体积能量密度D相同以及不同的情况，进一步选择K值比例的优选范围，可以持续改善电池包整体的低温性能和安全性能的平衡。所述电池单体的体积能量密度D可通过测量电池单体的放电容量，并除以该电池单体的体积而得到，即，D＝电池单体的放电容量/电池单体的体积，基本单位为Wh/L(瓦时/升)。电池单体的体积能量密度D主要与该电池单体的阴极、阳极、隔膜等主材料及其比例相关，因此可通过选择具体的主材料及其比例来调节体积能量密度D的大小。电池单体的电解液在-10℃下的离子电导率σ可使用电导率仪在相应温度下直接测量得到。对于给定体系的电池单体，可通过选择具体的电解液的离子种类以及溶剂、助溶剂和添加剂的种类和比例来调节其电解液的离子电导率σ。
在一些实施方案中，当D1＝D2时，所述第一类电池单体和第二类电池单体的电解液在-10℃下的离子电导率σ1和σ2满足0<|σ1-σ2|<8mS/cm；可选地，0.05mS/cm<|σ1-σ2|<7mS/cm；进一步可选地，0.1mS/cm<|σ1-σ2|<6mS/cm。在所述两类电池单体的体积能量密度D相同时，通过限定二者的离子电导率σ的差值的绝对值范围，可以有利地调节所述电池包的低温性能和安全性能的平衡，也可以避免过设计导致的容量 发挥、性能以及成本等方面的较大浪费。在一些实施方案中，所述电解液的离子电导率σ在-10℃的总范围限定为0.5-15mS/cm，可选地为1-10mS/cm。
本申请第二方面提供另外一种电池包，其包括至少第一类电池单体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且B区域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，
其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的粘度η分别为η1和η2，定义M＝D/η，则M1＝D1/η1且M2＝D2/η2，其中：
当D1＝D2时，M值满足0.2<M2/M1≤0.99；并且
当D1≠D2时，M值满足1.01≤M2/M1≤10。
对于上述本申请第二方面限定的电池包，当其中包含的两类电池单体的体积能量密度相同时，即表现为两类电池使用的阴极、阳极以及隔膜等主材料及其比例相同。此时仅改变这两类电池单体的电解液的低温粘度，使电池包的保温薄弱区域放置的电池单体具有更高的低温放电能力，同时不恶化电池包的安全性能。另外，将低温粘度比例控制在较为合理的范围内，避免容量发挥、性能、成本等方面的较大浪费，从而达到补充低温薄弱区续航以及功率短板的同时，兼顾电池包的整体安全性能的技术效果。
当其中包含的两类电池单体的体积能量密度不同时，即表现为这两类电池使用的主材料体系或主材料成分占比不同。按照锂离子电池体系中的经验，体积能量密度D更高的电池通常安全性能相对较差。因为体积能量密度D影响了电池热失控后的剧烈程度以及向周围热辐射的速度，其通常 与安全性能成反比，即1/D越大越安全。同时，高能量密度的体系低温放电能力往往更有优势，因此通常搭配使用的电解液体系，针对降低低温下粘度的需求相对较低。基于以上规律，电池包中使用锂离子电池中不同体系电芯的搭配，设定M＝D/η，M值越小的体系，越适合放在保温薄弱区域。通过M值比例的范围限定，补充低温薄弱区短板的同时，又保证了电池包的整体具有较高的安全性能。
因此，通过选择这两类电池单体的体积能量密度D以及其电解液在低温下的粘度η，并将其比值M＝D/η设定在合适的范围内，可实现对于不同种类的电池单体进行搭配和差异化排布，使得所述电池包可以兼具良好的低温性能以及同时优异的整体安全性能。
在一些实施方案中，当D1＝D2时，M值满足0.25≤M2/M1≤0.98；可选地，0.3≤M2/M1≤0.96。当D1≠D2时，M值满足1.02≤M2/M1≤9；可选地，1.03≤M2/M1≤8。通过假定两种电池单体的体积能量密度D相同或不同的情况，进一步优选二者M值的比例，可实现对于所述电池包的低温性能以及整体安全性能的极佳平衡。
在一些实施方案中，当D1＝D2时，所述第一类电池单体和第二类电池单体的电解液在-10℃下的粘度η1和η2满足0<|η2-η1|<5mPa·s；可选地，0.05mPa·s<|η2-η1|<4mPa·s；进一步可选地，0.1mPa·s<|η2-η1|<3mPa·s。通过设定两种电池单体的粘度η的差值的绝对值，可以方便地调节所述电池包在低温性能以及整体安全性能的平衡状况，同时避免过设计导致的容量发挥/性能/成本等方面的较大浪费。在一些实施方案中，所述电解液的粘度η在-10℃下的总范围限定为3-20mPa s，可选地为5-15mPa s。
在一些实施方案中，所述A区域所包含的电池单体中所述第一电池单体的数量占比为10％至90％，可选地为20％至90％，进一步可选地为 20％至80％，并且所述B区域所包含的电池单体中所述第二电池单体的数量占比为20％至100％，可选地为40％至100％，进一步可选地为60％至100％。A区域和B区域中第一电池单体和第二电池单体的数量占比可根据各电池单体的K值和M值来调整。
在一些实施方案中，所述电池包在水平方向上的长宽对角线为Lc，在两条所述对角线距离端点各自1/5Lc等分点处的四个点相连所围成的区域定义为B区域，剩余区域定义为A区域。由此所形成的A区域由于处在所述电池包的相对外围，其保温能力相对于内部区域较差。当电池包在低温下工作时，处于其A区域内的电池单体需要具有相对更强的低温放电能力。但是，A区域由于处于外围，其安全性也较差，因此需要对其中的电池单体的低温放电能力和安全性能进行总体规划，使其达到平衡。相应地，B区域处于相对内部，其保温能力较好，同时安全性也较好。在水平方向上A区域和B区域的划分合理地界定了所述两种具有不同性能的电池单体的空间分布。
在一些实施方案中，当所述电池包中的电池单元为多层重叠放置时，将所述电池包的垂直高度定义为Ld，位于底部1/5Ld处以下的区域定义为A区域，剩余上方4/5Ld的区域定义为B区域。通过对所述电池包在垂直方向上也进行空间划分，可以构建立体的电池包性能分布，其可与上文所述水平方向上的A区域和B区域的划分方式相结合，从而实现对于电池包低温性能以及整体安全性能的最佳平衡。Lc和Ld的数值范围不是重点，其均可由技术人员根据需要以及合理配置的要求进行选择。
在一些实施方案中，所述电池包具有长方体的结构，其水平面内为长方形，长度为La，宽度为Lb，长宽对角线为Lc，并且其垂直高度为Ld。
在一些实施方案中，所述电池包中不同区域具有不同的保温能力，且至少有两类区域满足温度差值ΔT的范围为0<ΔT<10℃；可选地，0.1<Δ T<9℃；进一步可选地，0.2<ΔT<8℃。通过设定所述电池包中至少两个区域的温度差值的范围，有助于差异化排布的效果体现，同时提升电池包温度的均一性。所述电池包中至少有两类区域存在大于0℃的温度差值ΔT，才能形成温度的梯度，以便于不同性能的电池单体实现平衡；而当所述温度差值ΔT过大时，将使电池包内的平衡变得困难。
在一些实施方案中，所述第一类电池单体和第二类电池单体中正极极片的成膜阻抗分别为Rct1和Rct2，二者满足关系：1≤Rct1/Rct2≤4；可选地，1.01≤Rct1/Rct2≤3.5；进一步可选地，1.02≤Rct1/Rct2≤3。所述两类电池单体的成膜阻抗的比值范围可进一步区分二者的放电能力，有助于改善所述电池包的性能平衡。成膜阻抗反映了所述电池单体的放电能力，二者的比值须在合理的范围内，以便于对不同电池单体的空间排布进行调整来实现精准的平衡。Rct作为低温放电的使用场景中重要的参数，其值越小，低温性能越好。将Rct比值控制在合理的范围内，保证了低温改善效果同时避免过设计。
在一些实施方案中，所述电池包中的所有电池单体的电解液的凝固点≤-20℃，可选地≤-30℃。将所述电池单体的电解液的凝固点设置在该范围内，可确保所述电池包在低温下具有良好的放电能力。当所述凝固点过高时，当电池包在低温下长时间工作后，电解液中的离子迁移能力将严重下降，不利于低温性能的发挥。通过设定所述电池单体的电解液的凝固点的上限值，可确保所述电池包在低温下具有良好的放电能力，凝固点越低，则低温应用的窗口越宽。
在一些实施方案中，所述第一类电池单体和第二类电池单体的体积能量密度D均满足100Wh/L<D<1000Wh/L；可选地，200Wh/L<D<900Wh/L；进一步可选地，300Wh/L<D<800Wh/L。所述两类电池单体的体积能量密度D的数值范围可进一步实现对于所述电池包的低 温性能的调节。同时，选择合适的能量密度范围的材料体系，可使其具有良好的落地应用价值和产品竞争力，以便更好地匹配各类应用场景的续航和功率需求。
在一些实施方案中，当D1≠D2时，还包含第三类电池单体，其为使用第一类电池单体和第二类类电池单体的主材料体系进行物混而形成，所述第三类电池单体具有体积能量密度D3，其中D3介于D1和D2之间。在一些实施方案中，所述第三类电池单体的电解液在-10℃下的离子电导率σ为σ3，定义K3＝D3 2×σ3，K3介于K1与K2之间；或者所述第三类电池单体的电解液在-10℃下的粘度η为η3，定义M3＝D3/η3，M3介于M1与M2之间。通过在上述两类电池单体以外再设置第三类或者其他的电池单体，可更加精确地控制和调节所述电池包的低温性能和整体安全性能，使其更容易达到平衡。所述第三类电池单体的设置可拓展电池包的性能调节范围，使得电池单体的选择不只限于不同纯体系的电池搭配，也可覆盖各类掺混体系与纯体系间的的搭配。
在一些实施方案中，所述电池单体分别独立地选自锂离子电池、锂金属电池以及钠离子电池。在一些实施方案中，所述电池单体的正极活性材料的化学体系独立地选自锂镍钴锰、磷酸铁锂、磷酸锰铁锂、磷酸钒铁锂、磷酸钒锂、钴酸锂、镍酸锂、富锂锰、锂镍钴铝和锰酸锂体系，以及普鲁士蓝类、聚阴离子类、氧化物类、双离子电池体系。所述电池单体的体系的选择可使得电池包的性能更加丰富和可调。
在一些实施方案中，所述电池包包含a个第一类电池单体和b个第二类电池单体，其中a和b均为≥1的自然数，并且0.01＜a/b≤200；可选地，0.05≤a/b≤180；进一步可选地0.1≤a/b≤150。所述两类电池单体的数量之比控制在合理范围内，可有效地调节所述电池包的低温性能和安全性能。
下面对电池包中所包含的电池单体进行详细阐述。在一些实施方式中，所述第一类电池单体和第二类电池单体均为锂离子二次电池。如上所述，所述电池单体也可选择其它体系的电池单体，如钠离子电池。
通常情况下，锂离子二次电池包括正极极片、负极极片、隔离膜及电解质。在电池充放电过程中，活性离子在正极极片和负极极片之间往返嵌入和脱出。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。电解质在正极极片和负极极片之间起到传导离子的作用。
[电解液]
电解液在正极极片和负极极片之间起到传导离子的作用。电解液包括电解质盐和溶剂。
在本申请中，电解质盐可为锂离子二次电池中的常用电解质盐，例如锂盐，包括可为上述作为高热稳定性盐的锂盐、作为低阻抗添加剂的锂盐或抑制铝箔腐蚀的锂盐。作为实例，电解质盐可选自六氟磷酸锂(LiPF 6)、四氟硼酸锂(LiBF 4)、六氟砷酸锂(LiAsF 6)、双氟磺酰亚胺锂(LiFSI)、双三氟甲磺酰亚胺锂(LiTFSI)、三氟甲磺酸锂(LiTFS)、二氟草酸硼酸锂(LiDFOB)、二氟磷酸锂(LiPO 2F 2)、二氟二草酸磷酸锂(LiDFOP)、氟磺酸锂(LiSO 3F)、二氟二草酸盐(NDFOP)、Li 2F(SO 2N) 2SO 2F、KFSI、CsFSI、Ba(FSI) 2及LiFSO 2NSO 2CH 2CH 2CF 3中的一种以上。
所述溶剂的种类没有特别的限制，可根据实际需求进行选择。在一些实施方式中，所述溶剂为非水性溶剂。可选地，所述溶剂可包括链状碳酸酯、环状碳酸酯、羧酸酯中的一种或几种。在一些实施方式中，溶剂可选自碳酸亚乙酯(EC)、碳酸亚丙酯(PC)、碳酸甲乙酯(EMC)、碳酸二乙酯(DEC)、碳酸二甲酯(DMC)、碳酸二丙酯(DPC)、碳酸甲丙酯(MPC)、碳酸乙丙酯(EPC)、碳酸亚丁酯(BC)、氟代碳酸亚乙酯 (FEC)、甲酸甲酯(MF)、乙酸甲酯(MA)、乙酸乙酯(EA)、乙酸丙酯(PA)、丙酸甲酯(MP)、丙酸乙酯(EP)、丙酸丙酯(PP)、丁酸甲酯(MB)、丁酸乙酯(EB)、1,4-丁内酯(GBL)、四氢呋喃、环丁砜(SF)、二甲砜(MSM)、甲乙砜(EMS)及二乙砜(ESE)中的一种以上。
在一些实施方式中，所述电解液中还可选地包括其他添加剂。例如添加剂可以包括负极成膜添加剂，也可以包括正极成膜添加剂，还可以包括能够改善电池某些性能的添加剂，例如改善电池过充性能的添加剂、改善电池高温性能的添加剂、以及改善电池低温性能的添加剂等。作为示例，所述添加剂选自含有不饱和键的环状碳酸酯化合物、卤素取代的环状碳酸酯化合物、硫酸酯化合物、亚硫酸酯化合物、磺酸内酯化合物、二磺酸化合物、腈化合物、芳香化合物、异氰酸酯化合物、磷腈化合物、环状酸酐化合物、亚磷酸酯化合物、磷酸酯化合物、硼酸酯化合物、羧酸酯化合物中的至少一种。
[正极极片]
正极极片包括正极集流体以及设置在正极集流体至少一个表面的正极材料层，所述正极材料层包括正极活性物质和碳。
作为示例，正极集流体具有在其自身厚度方向相对的两个表面，正极材料层设置在正极集流体相对的两个表面的其中任意一者或两者上。
本申请的锂离子二次电池中，所述正极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可采用铝箔。复合集流体可包括高分子材料基层和形成于高分子材料基层至少一个表面上的金属层。复合集流体可通过将金属材料(例如铝、铝合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯 (PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
设置于正极集流体的表面上的正极材料层包括正极活性物质。本申请中所用的正极活性物质可具有如上文所述的式(I)、式(II)、式(III)或式(IV)的结构以及其中限定的各种数值定义。可选地，所述式(I)、式(II)、式(III)或式(IV)的正极活性物质在每种情况下占该种电池单体的正极活性物质总重量的60-100重量％，可选地为80-100重量％。在一些实施方式中，所述正极活性物质除了上述物质之外，还可包含其他选自锂过渡金属氧化物、橄榄石结构的含锂磷酸盐及其各自的改性化合物中的一种或几种。锂过渡金属氧化物的示例可包括但不限于锂钴氧化物、锂镍氧化物、锂锰氧化物、锂镍钴氧化物、锂锰钴氧化物、锂镍锰氧化物、锂镍钴锰氧化物、锂镍钴铝氧化物及其改性化合物中的一种或几种。橄榄石结构的含锂磷酸盐的示例可包括但不限于磷酸铁锂、磷酸铁锂与碳的复合材料、磷酸锰锂、磷酸锰锂与碳的复合材料、磷酸锰铁锂、磷酸锰铁锂与碳的复合材料及其改性化合物中的一种或几种。这些材料均可以通过商业途径获得。正极活性物质表面上可包覆有碳。
正极材料层可选地包括导电剂。但对导电剂的种类不做具体限制，本领域技术人员可以根据实际需求进行选择。作为示例，用于正极材料的导电剂可以选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
正极材料层还可选地包括粘结剂。作为示例，粘结剂可以为丁苯橡胶(SBR)、水性丙烯酸树脂、聚偏二氟乙烯(PVDF)、聚四氟乙烯(PTFE)、乙烯-醋酸乙烯酯共聚物(EVA)、聚丙烯酸(PAA)、羧甲基纤维素(CMC)、聚乙烯醇(PVA)及聚乙烯醇缩丁醛(PVB)中的一种或几种。
本申请中可按照本领域已知的方法制备正极极片。作为示例，可以将包覆碳的正极活性物质、导电剂和粘结剂分散于溶剂(例如N-甲基吡咯烷酮(NMP))中，形成均匀的正极浆料；将正极浆料涂覆在正极集流体上，经烘干、冷压等工序后，得到正极极片。
[负极极片]
负极极片包括负极集流体以及设置在负极集流体至少一个表面上的负极材料层，所述负极材料层包括负极活性物质。
作为示例，负极集流体具有在其自身厚度方向相对的两个表面，负极材料层设置在负极集流体相对的两个表面中的任意一者或两者上。
本申请的锂离子二次电池中，所述负极集流体可采用金属箔片或复合集流体。例如，作为金属箔片，可以采用铜箔。复合集流体可包括高分子材料基层和形成于高分子材料基材至少一个表面上的金属层。复合集流体可通过将金属材料(例如铜、铜合金、镍、镍合金、钛、钛合金、银及银合金等)形成在高分子材料基材(如聚丙烯(PP)、聚对苯二甲酸乙二醇酯(PET)、聚对苯二甲酸丁二醇酯(PBT)、聚苯乙烯(PS)、聚乙烯(PE)等的基材)上而形成。
本申请的锂离子二次电池中，所述负极材料层通常包含负极活性物质以及可选的粘结剂、可选的导电剂和其他可选助剂，通常是由负极浆料涂布干燥而成的。负极浆料涂通常是将负极活性物质以及可选的导电剂和粘结剂等分散于溶剂中并搅拌均匀而形成的。溶剂可以是N-甲基吡咯烷酮(NMP)或去离子水。
所述负极活性物质的具体种类不做限制，可以采用本领域已知的能够用于锂离子二次电池负极的活性物质，本领域技术人员可以根据实际需求进行选择。作为示例，负极活性物质可选自石墨、软碳、硬碳、中间相碳 微球、碳纤维、碳纳米管、单质硅、硅氧化合物、硅碳复合物、钛酸锂中的一种或几种。
作为示例，导电剂可选自超导碳、乙炔黑、炭黑、科琴黑、碳点、碳纳米管、石墨烯及碳纳米纤维中的一种以上。
作为示例，粘结剂可选自丁苯橡胶(SBR)、聚丙烯酸(PAA)、聚丙烯酸钠(PAAS)、聚丙烯酰胺(PAM)、聚乙烯醇(PVA)、海藻酸钠(SA)、聚甲基丙烯酸(PMAA)及羧甲基壳聚糖(CMCS)中的一种以上。
其他可选助剂例如是增稠剂(如羧甲基纤维素钠(CMC-Na))等。
[隔离膜]
采用电解液的锂离子二次电池中还包括隔离膜。隔离膜设置在正极极片和负极极片之间，起到隔离的作用。本申请对隔离膜的种类没有特别的限制，可以选用任意公知的具有良好的化学稳定性和机械稳定性的多孔结构隔离膜。在一些实施方式中，隔离膜的材质可选自玻璃纤维、无纺布、聚乙烯、聚丙烯及聚偏二氟乙烯中的一种以上。隔离膜可以是单层薄膜，也可以是多层复合薄膜，没有特别限制。在隔离膜为多层复合薄膜时，各层的材料可以相同或不同，没有特别限制。
在一些实施方式中，正极极片、负极极片和隔离膜可通过卷绕工艺或叠片工艺制成电极组件。
在一些实施方式中，锂离子二次电池可包括外包装。该外包装可用于封装上述电极组件及电解质。
在一些实施方式中，锂离子二次电池的外包装可以是硬壳，例如硬塑料壳、铝壳、钢壳等。锂离子二次电池的外包装也可以是软包，例如袋式软包。软包的材质可以是塑料，作为塑料，可列举出聚丙烯(PP)、聚对苯二甲酸丁二醇酯(PBT)以及聚丁二酸丁二醇酯(PBS)等。
本申请对锂离子二次电池的形状没有特别的限制，其可以是圆柱形、方形或其他任意的形状。例如，图1是作为一个示例的方形结构的锂离子二次电池5。
在一些实施方式中，参照图2，外包装可包括壳体51和盖板53。其中，壳体51可包括底板和连接于底板上的侧板，底板和侧板围合形成容纳腔。壳体51具有与容纳腔连通的开口，盖板53能够盖设于所述开口，以封闭所述容纳腔。正极极片、负极极片和隔离膜可经卷绕工艺或叠片工艺形成电极组件52。电极组件52封装于所述容纳腔内。电解液浸润于电极组件52中。锂离子二次电池5所含电极组件52的数量可以为一个或多个，本领域技术人员可根据具体实际需求进行选择。
在一些实施方式中，锂离子二次电池可以组装成电池模块4，电池模块4所含锂离子二次电池的数量可以为一个或多个，具体数量本领域技术人员可根据电池模块4的应用和容量进行选择。在电池模块4中，多个锂离子二次电池5可以是沿电池模块的长度方向依次排列设置。当然，也可以按照其他任意的方式进行排布。进一步可以通过紧固件将该多个锂离子二次电池5进行固定。可选地，电池模块4还可以包括具有容纳空间的外壳，多个锂离子二次电池5容纳于该容纳空间。
在一些实施方式中，上述锂离子二次电池5或者电池模块4可以组装成电池包1，电池包1所含锂离子二次电池5或者电池模块4的数量可由本领域技术人员根据电池包1的应用和容量进行选择。
图3和图4是作为一个示例的电池包1。参照图3和图4，在电池包1中可以包括电池箱和设置于电池箱中的多个电池单体。电池箱包括上箱体2和下箱体3，上箱体2能够盖设于下箱体3，并形成用于容纳电池单体的封闭空间。
图5是本申请的一个实施方式中的电池包的区域划分以及电池单体排布的示意图。其中在图5(a)中，电池包水平方向的长度La，宽度为Lb，长宽对角线为Lc，将两条长宽对角线Lc的距离端点各自1/5Lc等分点处的4个点相连所围成的区域定义为B区域，剩余区域定义为A区域。在图5(b)中，将电池包的垂直高度定义为Ld，位于底部1/5Ld处以下的区域定义为A区域，剩余上方4/5Ld的区域定义为B区域。电池单体按照本申请所描述的种类和数量占比放置于对应区域中，从而实现不同区域放电性能的调节。
另外，本申请还提供一种装置，所述装置包括本申请提供的电池包。所述电池包可以用作所述装置的电源，也可以用作所述装置的能量存储单元。所述装置可以但不限于是移动设备(例如手机、笔记本电脑等)、电动车辆(例如纯电动车、混合动力电动车、插电式混合动力电动车、电动自行车、电动踏板车、电动高尔夫球车、电动卡车等)、电气列车、船舶及卫星、储能系统等。
作为所述装置，可以根据其使用需求来选择电池包。
图6是作为一个示例的装置。该装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该装置对锂离子二次电池的高功率和高能量密度的需求，可以采用电池包或电池模块。
实施例
以下，说明本申请的实施例。下面描述的实施例是示例性的，仅用于解释本申请，而不能理解为对本申请的限制。实施例中未注明具体技术或条件的，按照本领域内的文献所描述的技术或条件或者按照产品说明书进行。所用试剂或仪器未注明生产厂商者，均为可以通过市购获得的常规产品。
1.电池单元各参数以及电池包性能测试方法如下：
1)体积能量密度测定：
D＝电池单体初始放电容量×放电电压平台/电池单体体积
电池单体初始放电容量定义为25℃从每个电池单体的上限截止电压开始，以0.33C的倍率进行放电至每个电池单体的下限截止电压的容量；
放电电压平台定义为25℃从每个电池单体的上限截止电压开始，以0.33C的倍率进行放电至每个电池单体的下限截止电压的平均放电电压。
2)电解液电导率测定：
用设备型号雷磁DDSJ-318电导率测试仪对电解液电导率进行测试，首先将电极探头置于标准电解液中进行标定，之后置于待测电解液中，待环境温度稳定后进行测量，重复测量三次，取平均值，保留两位小数。
3)电解液粘度测定：
根据GB/T 10247-2008进行测定，温度设定为-10℃。
4)电池包容量保持率测试：
25℃放电容量测试：将电池包置于25℃环境中，以固定倍率1/3C对锂离子电池进行充放电(1C＝电池单体额定容量)，重复此步骤三次，所取第三次放电容量记为电池包标称容量C1；
-20℃放电容量测试：将电池包置于-20℃环境中，以固定倍率1/3C1对锂离子电池进行放电，放电至截至下限电压，记录此时放电容量为C2；
-20℃电池包放电容量保持率：C2/C1比值即为电池包在-20℃放电容量保持率。
5)热蔓延测试：测试电池中某一电池单体由于针刺发生热失控后是否会蔓延至相邻电池单体。将两个或以上待测电池单体组成的测试电池模 组。将测试电池模组满充，选择带孔两片钢板夹具固定测试电池模组。用直径为8mm的耐高温不锈钢钢针(针角圆锥角度为45°，钢针表面光洁，无锈蚀、氧化层及油污)，以25mm/s的速度，从垂直于电池单体的极板的方向贯穿至第一个电池单体触发热失控，观察并记录相邻的第二个电芯发生热失控的时间；触发热失控的电池单体不引起相邻电池单体起火或者爆炸判定为热蔓延阻隔实现，否则判定为发生热蔓延。
2.电池单元的制备
1)NCM：
正极极片：将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)，导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为90:5:5溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，再经过烘干、冷压、分切，得到正极片。
负极极片：将活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:4:4:2溶于溶剂去离子水中与溶剂去离子水均匀混合后制备成负极浆料；然后将负极浆料一次或多次均匀涂覆在负极集流体铜箔上，烘干后得到负极膜片，再经过冷压、分切得到负极极片。
电解液：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂EC/EMC按照体积比3/7混合均匀，加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到相应的电解液。
电池制备：使用如上所述制得的正极极片和负极极片，以聚丙烯膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件。将电极组件 置于电池壳体中，干燥后注入电解液，再经过化成、静置，制得锂离子二次电池作为电池单体。
混合NCM：(仅举例，混合比例可根据需要调整)正极极片：将正极活性材料LiNi 0.8Co 0.1Mn 0.1O 2(NCM811)和包覆碳的磷酸铁锂(LFP)，导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为60:30:5:5溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，再经过烘干、冷压、分切，得到正极片。
负极极片：将活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:4:4:2溶于溶剂去离子水中与溶剂去离子水均匀混合后制备成负极浆料；然后将负极浆料一次或多次均匀涂覆在负极集流体铜箔上，烘干后得到负极膜片，再经过冷压、分切得到负极极片。
电解液：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂EC/EMC按照体积比3/7混合均匀，加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到相应的电解液。
电池制备：使用如上所述制得的正极极片和负极极片，以聚丙烯膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件。将电极组件置于电池壳体中，干燥后注入电解液，再经过化成、静置，制得锂离子二次电池作为电池单体。
2)LFP：
正极极片：将作为正极活性物质的包覆碳的磷酸铁锂(LFP)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按照重量比为96:2:2溶于溶剂 N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。另外，使用颗粒筛分机对所选择的磷酸铁锂颗粒材料以及磷酸锰铁锂颗粒材料进行筛分，将各种材料进一步筛分成具有不同体积平均粒径D50值的级分，并分别应用于不用电池单体的制备中。将正极浆料均匀涂覆于铝正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
负极极片：将负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比为95:2:2:1溶于溶剂去离子水中，均匀混合后制备成负极浆料。将负极浆料均匀涂覆在负极集流体铜箔上，烘干后经过冷压、分切得到负极极片。
电解液：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸亚乙酯(EC)、碳酸二甲酯(DMC)以及碳酸甲乙酯(EMC)分别按照表1和表2中列出的重量比均匀混合，加入六氟磷酸锂(LiPF 6)并调节至1M/L的浓度，搅拌均匀，得到相应的电解液。
电池制备：使用如上所述制得的正极极片和负极极片，以聚丙烯膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件。将电极组件置于电池壳体中，干燥后注入电解液，再经过化成、静置，制得锂离子二次电池作为电池单体。
3)磷酸锰铁锂(LMFP)：
正极极片：将作为正极活性物质磷酸锰铁锂LiMn 0.6Fe 0.4PO 4(LMFP)、导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按照重量比为96:2:2溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料。另外，使用颗粒筛分机对所选择的磷酸铁锂颗粒材料以及磷酸锰铁锂颗粒材料进行筛分，将各种材料进一步筛分成具有不同体积平均粒径 D50值的级分，并分别应用于不用电池单体的制备中。将正极浆料均匀涂覆于铝正极集流体上，之后经过烘干、冷压、分切，得到正极极片。
负极极片：将负极活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC-Na)按照重量比为95:2:2:1溶于溶剂去离子水中，均匀混合后制备成负极浆料。将负极浆料均匀涂覆在负极集流体铜箔上，烘干后经过冷压、分切得到负极极片。
电解液：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂碳酸亚乙酯(EC)、碳酸二甲酯(DMC)以及碳酸甲乙酯(EMC)分别按照表1和表2中列出的重量比均匀混合，加入六氟磷酸锂(LiPF 6)并调节至1M/L的浓度，搅拌均匀，得到相应的电解液。
电池制备：使用如上所述制得的正极极片和负极极片，以聚丙烯膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件。将电极组件置于电池壳体中，干燥后注入电解液，再经过化成、静置，制得锂离子二次电池作为电池单体。
4)SIB：
正极极片：将正极活性材料钠氧化物Na 2FeO 2，导电剂乙炔黑、粘结剂聚偏二氟乙烯(PVDF)按重量比为90:5:5溶于溶剂N-甲基吡咯烷酮(NMP)中，充分搅拌混合均匀后得到正极浆料；之后将正极浆料均匀涂覆于正极集流体上，再经过烘干、冷压、分切，得到正极片。
负极极片：将活性物质人造石墨、导电剂乙炔黑、粘结剂丁苯橡胶(SBR)、增稠剂羧甲基纤维素钠(CMC)按照重量比为90:4:4:2溶于溶剂去离子水中与溶剂去离子水均匀混合后制备成负极浆料；然后将负极浆 料一次或多次均匀涂覆在负极集流体铜箔上，烘干后得到负极膜片，再经过冷压、分切得到负极极片。
电解液：在氩气气氛手套箱中(H 2O<0.1ppm，O 2<0.1ppm)，将有机溶剂EC/EMC按照体积比3/7混合均匀，加入12.5％LiPF 6锂盐溶解于有机溶剂中，搅拌均匀，得到相应的电解液。
电池制备：使用如上所述制得的正极极片和负极极片，以聚丙烯膜作为隔离膜，将正极极片、隔离膜、负极极片按顺序叠好，使隔离膜处于正、负极极片之间起到隔离的作用，然后卷绕得到电极组件。将电极组件置于电池壳体中，干燥后注入电解液，再经过化成、静置，制得锂离子二次电池作为电池单体。
3.电池包的组装
调节上述各电池单体的主材料以及电解液中溶剂以及添加剂的种类、组成、用量以及电解质盐的种类、浓度等，获得具有如表1中所述电导率以及粘度比例的电解液以及体积能量密度的两类电池单体。将如上所述制备的具有不同主材料体系的电池单体按照表1中所示的数量和区域进行放置，得到实施例1-6以及对比例1-3中的具有不同电池单体排布的电池包。在本申请实施例1-6以及对比例1-3中，每个电池包仅含有两种选自如上文所述制备的电池单体，分别标记为第一类电池单体和第二类电池单体，如下表所示；其中，A区域为电池包的水平长宽对角线Lc距离端点各自1/5Lc等分点处的四个点相连所围成的区域以及位于距底部1/5垂直高度Ld处以下的区域，电池包的其余区域为B区域。A区域中包含的所有电池单体的数量为48个，其中第一类电池单体的数量为40个，第二类电池单体的数量为8个；B区域中包含的所有电池单体的数量为72个，其中第一类电池单体的数量为27个，第二类电池单体的数量为45个。
对各实施例中所制备的电池包进行测试，测试结果显示于表1中。
表1：实施例1-6和对比例1-3的电池包的相应参数测试结果
Figure PCTCN2022099470-appb-000001
由表1可见，当电池包中两类电池单体的体积能量密度D相等时，K2/K1或者M2/M1的值小于1可使得电池包具有较高的容量保持率，同时满足热蔓延阻隔的要求，如实施例1所示。相反，如对比例1所示，对于同样的NCM电池单体，当K2/K1或者M2/M1的值为1时，电池包的容量保持率降低，并且无法通过热蔓延阻隔测试。同样，对于LFP体系的电池单体，当电池包中两类电池单体的体积能量密度D相等时，K2/K1或者M2/M1的值为1使得电池包具有严重降低的容量保持率(对比例2)。
另外，当使用不同体系的电池单体组成混合体系电池包时，二者的体积能量密度不同，则K2/K1或者M2/M1的值大于1带来了相对较高的容 量保持率，同时均满足热蔓延阻隔的要求，如实施例2-6所示。针对不同的电池体系，其容量保持率与具体使用的电池体系有关，而与其K2/K1或者M2/M1的值不成等比例变化。但是，当混合体系中K2/K1或者M2/M1的值小于1时，电池包的容量保持率有所降低，并且无法通过热蔓延阻隔测试(对比例3)。
虽然已经参考实施例对本申请进行了描述，但在不脱离本申请的范围的情况下，可以对其进行各种改进并且可以用等效物替换其中的部件。尤其是，只要不存在结构冲突，各个实施例中所提到的各项技术特征均可以任意方式组合起来。本申请并不局限于文中公开的特定实施例，而是包括落入权利要求的范围内的所有技术方案。

Claims (21)

  1. 一种电池包，其包括至少第一类电池单体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中所述A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且所述B区域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，
    其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的离子电导率σ分别为σ1和σ2，定义K＝D 2×σ，则K1＝D1 2×σ1且K2＝D2 2×σ2，其中：
    当D1＝D2时，K值满足0.2<K2/K1≤0.99；并且
    当D1≠D2时，K值满足1.01≤K2/K1≤10。
  2. 根据权利要求1所述的电池包，其中当D1＝D2时，K值满足0.25≤K2/K1≤0.98；可选地，0.3≤K2/K1≤0.96。
  3. 根据权利要求1所述的电池包，其中当D1≠D2时，K值满足1.02≤K2/K1≤5；可选地，1.03≤K2/K1≤3。
  4. 根据权利要求1或2中所述的电池包，其中当D1＝D2时，所述第一类电池单体和第二类电池单体的电解液在-10℃下的离子电导率σ1和σ2满足0<|σ1-σ2|<8mS/cm；可选地，0.05mS/cm<|σ1-σ2|<7mS/cm；进一步可选地，0.1mS/cm<|σ1-σ2|<6mS/cm。
  5. 一种电池包，其包括至少第一类电池单体和第二类电池单体，所述电池包包含A区域和B区域，其中所述A区域为保温能力较差的区域，位于所述电池包的四周和/或底部，剩余区域为B区域，其中A区域所包含的电池单体中所述第一电池单体的数量占比为10％至100％，并且B区 域所包含的电池单体中所述第二电池单体的数量占比为5％至100％，
    其中所述第一类电池单体和第二类电池单体的体积能量密度D分别为D1和D2，且各自搭配的电解液在-10℃下的粘度η分别为η1和η2，定义M＝D/η，则M1＝D1/η1且M2＝D2/η2，其中：
    当D1＝D2时，M值满足0.2<M2/M1≤0.99；并且
    当D1≠D2时，M值满足1.01≤M2/M1≤10。
  6. 根据权利要求5所述的电池包，其中当D1＝D2时，M值满足0.25≤M2/M1≤0.98；可选地，0.3≤M2/M1≤0.96。
  7. 根据权利要求5所述的电池包，其中当D1≠D2时，M值满足1.02≤M2/M1≤9；可选地，1.03≤M2/M1≤8。
  8. 根据权利要求5或6所述的二次电池，其中当D1＝D2时，所述第一类电池单体和第二类电池单体的电解液在-10℃下的粘度η1和η2满足0<|η2-η1|<5mPa·s；可选地，0.05mPa·s<|η2-η1|<4mPa·s；进一步可选地，0.1mPa·s<|η2-η1|<3mPa·s。
  9. 根据权利要求1至8中任一项所述的电池包，其中所述A区域所包含的电池单体中所述第一电池单体的数量占比为10％至90％，可选地为10％至90％，进一步可选地为20％至80％，并且所述B区域所包含的电池单体中所述第二电池单体的数量占比为20％至100％，可选地为40％至100％，进一步可选地为60％至100％。
  10. 根据权利要求1至9中任一项所述的电池包，其中所述电池包在水平方向上的长宽对角线为Lc，在两条所述对角线距离端点各自1/5Lc等分点处的四个点相连所围成的区域定义为B区域，剩余区域定义为A区域。
  11. 根据权利要求1至10中任一项所述的电池包，其中当所述电池包中的电池单元为多层重叠放置时，将所述电池包的垂直高度定义为Ld，位 于底部1/5Ld处以下的区域定义为A区域，剩余上方4/5Ld的区域定义为B区域。
  12. 根据权利要求1至11中任一项所述的电池包，其中所述电池包中不同区域具有不同的保温能力，且至少有两类区域满足温度差值ΔT的范围为0<ΔT<10℃；可选地，0.1<ΔT<9℃；进一步可选地，0.2<ΔT<8℃。
  13. 根据权利要求1至12中任一项所述的电池包，其中所述第一类电池单体和第二类电池单体中正极极片的成膜阻抗分别为Rct1和Rct2，二者满足关系：1≤Rct1/Rct2≤4；可选地，1.01≤Rct1/Rct2≤3.5；进一步可选地，1.02≤Rct1/Rct2≤3。
  14. 根据权利要求1至13中任一项所述的电池包，其中所述电池包中的所有电池单体的电解液的凝固点≤-20℃，可选地≤-30℃。
  15. 根据权利要求1至14中任一项所述的电池包，其中所述第一类电池单体和第二类电池单体的体积能量密度D均满足100Wh/L<D<1000Wh/L；可选地，200Wh/L<D<900Wh/L；进一步可选地，300Wh/L<D<800Wh/L。
  16. 根据权利要求1至15中任一项所述的电池包，其中当D1≠D2时，还包含第三类电池单体，其为使用第一类电池单体和第二类类电池单体的主材料体系进行物混而形成，所述第三类电池单体具有体积能量密度D3，其中D3介于D1和D2之间。
  17. 根据权利要求16所述的电池包，其中
    所述第三类电池单体的电解液在-10℃下的离子电导率σ为σ3，定义K3＝D3 2×σ3，K3介于K1与K2之间；或者
    所述第三类电池单体的电解液在-10℃下的粘度η为η3，定义M3＝D3/η3，M3介于M1与M2之间。
  18. 根据权利要求1至17中任一项所述的电池包，其中所述电池单体分别独立地选自锂离子电池、锂金属电池以及钠离子电池。
  19. 根据权利要求18所述的电池包，其中所述电池单体的正极活性材料的化学体系独立地选自锂镍钴锰、磷酸铁锂、磷酸锰铁锂、磷酸钒铁锂、磷酸钒锂、钴酸锂、镍酸锂、富锂锰、锂镍钴铝和锰酸锂体系，以及普鲁士蓝类、聚阴离子类、氧化物类、双离子电池体系。
  20. 根据权利要求1至19中任一项所述的电池包，其包含a个第一类电池单体和b个第二类电池单体，其中a和b均为≥1的自然数，并且0.01＜a/b≤200；可选地，0.05≤a/b≤180；进一步可选地0.1≤a/b≤150。
  21. 一种用电装置，其包括权利要求1至20中任一项所述的电池包。
PCT/CN2022/099470 2022-06-17 2022-06-17 一种电池包及其用电装置 WO2023240599A1 (zh)

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JP2010170874A (ja) * 2009-01-23 2010-08-05 Toyota Motor Corp 組電池システム及び組電池の劣化検知方法
US20120263999A1 (en) * 2011-04-12 2012-10-18 Hitachi, Ltd. Lithium-ion rechargeable battery module, vehicle with the battery module and generating system with the battery module
CN107004920A (zh) * 2014-12-26 2017-08-01 三洋电机株式会社 电池组
CN109196710A (zh) * 2015-12-11 2019-01-11 加拿大蓝色解决方案有限公司 具有有着可变阻抗的电化学电池单元的电池

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010170874A (ja) * 2009-01-23 2010-08-05 Toyota Motor Corp 組電池システム及び組電池の劣化検知方法
US20120263999A1 (en) * 2011-04-12 2012-10-18 Hitachi, Ltd. Lithium-ion rechargeable battery module, vehicle with the battery module and generating system with the battery module
CN107004920A (zh) * 2014-12-26 2017-08-01 三洋电机株式会社 电池组
CN109196710A (zh) * 2015-12-11 2019-01-11 加拿大蓝色解决方案有限公司 具有有着可变阻抗的电化学电池单元的电池

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