WO2024020935A1 - 电池包和用电装置 - Google Patents

电池包和用电装置 Download PDF

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Publication number
WO2024020935A1
WO2024020935A1 PCT/CN2022/108604 CN2022108604W WO2024020935A1 WO 2024020935 A1 WO2024020935 A1 WO 2024020935A1 CN 2022108604 W CN2022108604 W CN 2022108604W WO 2024020935 A1 WO2024020935 A1 WO 2024020935A1
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Prior art keywords
battery
battery pack
battery cell
temperature
cell
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PCT/CN2022/108604
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English (en)
French (fr)
Inventor
董苗苗
别常峰
欧阳少聪
倪欢
刘宏宇
孙信
付成华
Original Assignee
宁德时代新能源科技股份有限公司
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Priority to PCT/CN2022/108604 priority Critical patent/WO2024020935A1/zh
Priority to EP22938730.3A priority patent/EP4350835A1/en
Publication of WO2024020935A1 publication Critical patent/WO2024020935A1/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
    • H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
    • H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
    • H01M10/0566—Liquid materials
    • H01M10/0567—Liquid materials characterised by the additives
    • 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
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • 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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-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
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • 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
    • H01M50/233—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions
    • H01M50/24—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders characterised by physical properties of casings or racks, e.g. dimensions adapted for protecting batteries from their environment, e.g. from corrosion
    • 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 lithium-ion batteries, and in particular, to a battery pack with a high energy retention rate at low temperatures and an electrical device including the battery pack.
  • lithium-ion batteries are widely used in energy storage power systems such as hydraulic, thermal, wind and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, and military equipment. , aerospace and other fields.
  • the capacity of a lithium-ion secondary battery cell sometimes cannot meet the usage requirements.
  • multiple lithium-ion secondary battery cells need to be connected in series or in parallel to form a battery pack to increase the overall discharge capacity of the battery pack.
  • the present application was made in view of the above technical problems, and its purpose is to provide a battery pack composed of a lithium-ion secondary battery that has excellent energy retention at low temperatures and improved battery life at low temperatures, and a battery pack including the battery pack. Electrical devices.
  • a first aspect of the present application is a battery pack, which includes a battery pack box and battery cells stored in the battery pack box.
  • the battery pack is characterized in that, according to the determined Temperature distribution in the entire internal space of the battery pack box when used at low temperatures.
  • the internal space of the battery pack box includes the first area, the second area, and the third area in order from high to low temperature.
  • a first battery cell is arranged in the first area
  • a second battery unit is arranged in the second area
  • a third battery unit is arranged in the third area.
  • the first battery unit and the second battery unit are arranged in the first area.
  • the battery cells are arranged adjacently, and the second battery cell and the third battery cell are arranged adjacently,
  • the internal space of the battery pack box includes one or more first areas, second areas and/or third areas;
  • the positive electrodes of the first battery cell, the second battery cell, and the third battery cell each include a positive electrode active material, and the positive electrode active material is composed of the following substances:
  • Low temperature auxiliary agent which is selected from one or more of the following compounds: the compound contains at least two carbonyl groups, and the at least two carbonyl groups are individually or together with a double bond, an unsaturated monocyclic ring or a double bond connected thereto. Unsaturated fused rings, unsaturated groups, conjugated atoms containing lone pairs of electrons, and
  • the discharge capacity of the single cell of the first battery cell is CAP1
  • the discharge capacity of the single cell of the second battery cell is CAP2
  • the discharge capacity of the third battery cell is CAP2.
  • the discharge capacity of a single cell is CAP3, and the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship:
  • the value range of CAP3/CAP2 is 1.005 ⁇ 1.15, and
  • the value range of CAP2/CAP1 is 1.003 ⁇ 1.12.
  • the temperature distribution in the internal space of the battery pack can be determined through simulation methods, and then the internal space of the battery pack box is divided into regions in the direction from high to low temperature.
  • ANSYS-SCDM software Beijing Huanzhong Ruichi Technology Co., Ltd.
  • the steps are as follows:
  • the highest temperature in the third area is T 2 and the lowest temperature is TL ,
  • the internal area of the battery pack box space can be better divided. This division method enables the battery pack to better adapt to low-temperature environments.
  • Compounds having at least two carbonyl groups and the at least two carbonyl groups are conjugated with the unsaturated atoms, groups or structures connected thereto have excellent electrochemical redox properties within their own applicable voltage range, and are between 1.9 and 1.9 There is a relatively gentle voltage platform between 2.9V. Mixing them in the lithium iron phosphate system in an appropriate amount can slow down the decline of the discharge voltage when the voltage of the battery cell rapidly decays (below 3V) at the end of the discharge process, thus prolonging the discharge process. And improve the discharge power performance of the battery.
  • the discharge capacity of the single cell of the first battery cell is CAP1
  • the discharge capacity of the single cell of the second battery cell is CAP2
  • the discharge capacity of the third battery cell is CAP2.
  • the discharge capacity of a single cell is CAP3, and the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship:
  • the value range of CAP3/CAP2 is 1.005 ⁇ 1.15, and
  • the value range of CAP2/CAP1 is 1.003 ⁇ 1.12.
  • the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship: the value of CAP3/CAP2 ranges from 1.01 to 1.05, and the value of CAP2/CAP1 ranges from 1.01 to 1.05. It is 1.003 ⁇ 1.04. As a result, the discharge energy and total energy retention rate of the battery pack at low temperatures are further improved.
  • the theoretical gram capacity of the compound that can be used as a low temperature additive is in the range of 150-800 mAh/g, optionally in the range of 180-600 mAh/g. Therefore, by using a low-temperature additive with a theoretical gram capacity within the above range, it is possible to ensure that each battery cell has sufficient energy density and improve the low-temperature discharge power of each battery cell and the battery pack as a whole.
  • the gram capacity of the entire cathode active material of the first battery cell is 136-154 mAh/g
  • the gram capacity of the entire cathode active material of the second battery cell is 133-163 mAh/g
  • the overall gram capacity of the positive active material of the third battery cell is 128-172 mAh/g. Therefore, by setting the gram capacity of the entire positive electrode active material of each of the first battery cell, the second battery cell, and the third battery cell to be within the above range, it is possible to make the first battery cell, the second battery cell, and the third battery cell
  • the discharge capacities of the three battery cells at low temperatures are approximately the same, which improves the overall energy retention rate of the battery pack 1 at low temperatures.
  • the relative molecular weight of the compound that can be used as a low temperature auxiliary agent is in the range of 100-800.
  • the low temperature auxiliary agent is selected from simple quinones, substituted quinones, quinones fused with heterocyclic rings, polycarbonyl quinones, cyclic dianhydrides fused with unsaturated rings or cyclic Diimides and their salts, substituted or unsubstituted six-membered rings containing 3 or 4 carbonyl groups and 2 or 3 atoms containing lone pairs of electrons, 2-4 carbonyl groups and 1 - Alkoxides of a six-membered ring with two double bonds and without heterocyclic atoms, and carboxylates containing a benzene ring or double bond, and the benzene ring or double bond is conjugated with at least two carbonyl groups.
  • the low temperature auxiliary agent is selected from one or more of the following compounds: 1,4-dibenzoquinonebenzene, p-benzoquinone, o-benzoquinone, anthraquinone, phenanthrenequinone, 2,3,5 ,6-tetrahydro-1,4-benzoquinone, 2,5-dimethoxybenzoquinone, 1,3,4-trihydroxyanthraquinone, 1,5-dilithiumoxyanthraquinone, dipyridine Benzoquinone, dipyrido-o-benzoquinone, dithieno-p-benzoquinone, dithieno-o-benzoquinone, difuran-p-benzoquinone, nonbenzohexaquinone, 5,7,12,14-pentacenetetraquinone , pyromellitic anhydride, naphthalene tetracarboxylic acid dianhydride, perylene
  • the above-mentioned low-temperature additives have a reversible charge and discharge platform. After partially replacing lithium iron phosphate, they can alleviate the voltage attenuation through the auxiliary effect of the reversible charge and discharge platform when the battery is discharged at low SOC, thus improving the battery life. Core discharge power performance.
  • the mass proportion of the low-temperature additive is 0-13%, based on the positive electrode. Total mass of active substances. If the mass proportion of the low-temperature additive is greater than 13%, the content may be too high, resulting in excessive lithium supplementation for the corresponding negative electrode, which will increase production safety risks.
  • the mass proportion of the low-temperature additive in the respective positive electrodes of the first battery cells, is 0-2%, based on the total amount of the active material, the second battery In the positive electrode of each monomer, the mass proportion of the low-temperature additive is 2-8%, based on the total amount of the active material. In the positive electrode of each third battery cell, the mass proportion of the low-temperature additive is The mass proportion is 8-13%, based on the total amount of the active substance.
  • the mass proportion of the low-temperature additive in the first battery cell, the second battery cell and the third battery cell fall within the above range, the first battery cell, the second battery cell can be better balanced.
  • the discharge time of the single cell and the third battery cell is kept as consistent as possible, and can further improve the low-temperature energy retention rate and power performance of the overall battery pack.
  • a second aspect of the present application provides a method for arranging a battery pack.
  • the battery pack includes a battery pack box and battery cells accommodated in the battery pack box.
  • the method includes:
  • Step (1) Determine the temperature distribution in the entire internal space of the battery pack box when used at low temperatures based on the simulation method.
  • Step (2) According to the temperature distribution determined in step (1), divide the internal space of the battery pack box into three regions in order of temperature from high to low.
  • Step (3) Arrange a first battery cell in the first region, a second battery cell in the second region, and a third battery cell in the third region, so that the first battery cell
  • the body and the second battery cell are arranged adjacently, so that the second battery cell and the third battery cell are arranged adjacently,
  • the internal space of the battery pack box includes one or more first areas, second areas and/or third areas;
  • the positive electrodes of the first battery cell, the second battery cell, and the third battery cell each include a positive electrode active material, and the positive electrode active material is composed of the following substances:
  • Low temperature auxiliary agent which is selected from one or more of the following compounds: the compound contains at least two carbonyl groups, and the at least two carbonyl groups are individually or together with a double bond, an unsaturated monocyclic ring or a double bond connected thereto. Unsaturated fused rings, unsaturated groups, conjugated atoms containing lone pairs of electrons,
  • the discharge capacity of the single cell of the first battery cell is CAP1
  • the discharge capacity of the single cell of the second battery cell is CAP2
  • the discharge capacity of the third battery cell is CAP2.
  • the discharge capacity of a single cell is CAP3, and the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship:
  • the range of CAP3/CAP2 is 1.005 ⁇ 1.15, and
  • the range of CAP2/CAP1 is 1.003 ⁇ 1.12.
  • a third aspect of this application provides an electrical device, which includes the battery pack described in the first aspect of this application.
  • the battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a battery cell or a battery pack can be selected according to its usage requirements.
  • FIG. 4 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • the battery pack of the present application can be used.
  • Figure 1 is a schematic structural diagram of a battery pack according to an embodiment of the present application.
  • FIG. 2 is a top view of the structural components of the battery pack according to the embodiment of the present application shown in FIG. 1 with the case removed, when the internal space of the battery pack case is divided into three regions.
  • FIG 3 is a schematic diagram of the constant current discharge curve of a battery cell with dual discharge voltage platforms used in a battery pack according to an embodiment of the present application.
  • the positive active material of the battery cell is composed of lithium iron phosphate (LFP) and p-phenylene. Composed of quinones.
  • FIG. 4 is a schematic diagram of an electrical device using a battery pack as a power source according to an embodiment of the present application.
  • 1 battery pack 2 upper box; 3 lower box; gap between g1 and g2; BL1 first boundary line; BL2 second boundary line; BL3 third boundary line; R1 first area; R2 second area; R3 third Area; 61 first battery cell; 62 second battery cell; 63 third battery cell.
  • Ranges disclosed herein are defined in terms of lower and upper limits. A given range is defined by selecting a lower limit and an upper limit that define the boundaries of the particular range. Ranges defined in this manner may be inclusive or exclusive of the endpoints, and may be arbitrarily combined, that is, any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a particular parameter, understand that ranges of 60-110 and 80-120 are also expected. Furthermore, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2- 3, 2-4 and 2-6.
  • the numerical range “a-b” represents an abbreviated representation of any combination of real numbers between a and b, where a and b are both real numbers.
  • the numerical range “0-5" means that all real numbers between "0-5" have been listed in this article, and "0-5" is just an abbreviation of these numerical combinations.
  • a certain parameter is an integer ⁇ 2
  • it is equivalent to disclosing that the parameter is an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.
  • the numerical ranges "a-b” and “a-b” are used synonymously.
  • the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially.
  • step (c) means that step (c) may be added to the method in any order.
  • the method may include steps (a), (b) and (c). , may also include steps (a), (c) and (b), may also include steps (c), (a) and (b), etc.
  • condition "A or B” is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists) ; Or both A and B are true (or exist).
  • the inventor has repeatedly conducted research and found that the low-temperature capacity retention rate of the entire battery pack can be improved by allowing the battery cells arranged in a lower temperature area to have a lower discharge voltage platform. This is because after the discharge of the higher discharge voltage platform is completed, the lower discharge voltage platform can continue to be discharged, so that the discharge performance of these battery cells at low temperatures is better.
  • the first aspect of the present application is a battery pack, which includes a battery pack box and battery cells accommodated in the battery pack box.
  • the battery pack is characterized by:
  • the internal space of the battery pack box includes the first area, the second area, and the third area in order from high to low temperature.
  • a first battery cell is configured in the first region
  • a second battery cell is configured in the second region
  • a third battery cell is configured in the third region
  • the first battery cell is configured The body and the second battery cell are arranged adjacently
  • the second battery cell and the third battery cell are arranged adjacently
  • the internal space of the battery pack box includes one or more first areas, second areas and/or third areas;
  • the positive electrodes of the first battery cell, the second battery cell, and the third battery cell each include a positive electrode active material, and the positive electrode active material is composed of the following substances:
  • Low temperature auxiliary agent which is selected from one or more of the following compounds: the compound contains at least two carbonyl groups, and the at least two carbonyl groups are individually or together with a double bond, an unsaturated monocyclic ring or a double bond connected thereto. Unsaturated fused rings, unsaturated groups, conjugated atoms containing lone pairs of electrons,
  • the discharge capacity of the single cell of the first battery cell is CAP1
  • the discharge capacity of the single cell of the second battery cell is CAP2
  • the discharge capacity of the third battery cell is CAP2.
  • the discharge capacity of a single cell is CAP3, and the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship:
  • the value range of CAP3/CAP2 is 1.005 ⁇ 1.15, and
  • the value range of CAP2/CAP1 is 1.003 ⁇ 1.12.
  • the temperature distribution in the internal space of the battery pack can be determined through simulation methods, and then the internal space of the battery pack box is divided into regions in the direction from high to low temperature.
  • the interior of the battery pack box can be divided into 2 areas, 3 areas, or 4 areas, up to 5 areas, and preferably 3 areas.
  • only the situation of dividing into 3 areas is described in detail.
  • the situation of dividing into 2 areas, 4 areas, 5 areas, or even 6 areas is also feasible, as long as the outer areas ( The cut-off voltage of the nth region) is smaller than the cut-off voltage of the inner region (n-1th region, n is a natural number from 2 to 6), which is within the scope of the present application.
  • ANSYS-SCDM software Beijing Huanzhong Ruichi Technology Co., Ltd.
  • the steps are as follows:
  • the method of determining the temperature distribution in the internal space of the battery pack is not limited to the simulation method.
  • the concept of this application is based on the fact that the discharge of battery cells at different positions is different and the overall discharge capacity is reduced due to the difference in temperature distribution inside the battery pack during practical application at low temperatures. Therefore, all the conditions that can determine the actual application scenario
  • the methods of temperature distribution inside the battery pack are all within the scope of the present application.
  • the internal space of the battery pack box described in this application may include one or more, optionally only a first region, a second region and/or a third region.
  • the battery pack described in the first aspect of the present application will be described in detail, taking the case where the internal space of the battery pack box has a substantially rectangular shape as an example.
  • the battery pack of the present application is not limited to the case where the internal space of the battery pack case has a substantially rectangular shape.
  • FIG. 1 is a schematic structural diagram of a battery pack 1 according to an embodiment of the present application.
  • FIG. 2 is a top view of the structural components of the battery pack according to the embodiment of the present application shown in FIG. 1 with the case removed, when the internal space of the battery pack case is divided into three regions.
  • the battery pack 1 of the present application includes a battery box and a plurality of battery cells (61, 62, 63) 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 (battery pack cavity) for accommodating multiple battery cells.
  • the internal space of the battery pack box When the internal space of the battery pack box is divided into three areas, as shown in Figure 2, the internal space of the battery pack box includes a first area R1, a second area R2 and a third area R3.
  • the first area R1 is a substantially rectangular area surrounded by the first boundary line BL1 and is located at the center of the rectangular shape of the internal space of the battery pack box (for example, the length and width of the rectangular shape of the first area R1 may be respectively the length and width of the battery pack box).
  • the second area R2 is a substantially annular area between the first boundary line BL1 and the third boundary line BL3, and the third area R3 is the second boundary A substantially annular area between line BL2 and third boundary line BL3, where the first boundary line BL1, the second boundary line BL2, and the third boundary line BL3 are used to clearly represent the first area R1, the second area R2, and the third boundary line BL3.
  • a first battery cell 61 is configured in the first region R1
  • a second battery cell 62 is configured in the second region R2
  • a third battery is configured in the third region R3.
  • Cell 63 the second battery cell 62 is arranged around the first battery cell 61
  • the third battery cell 63 is arranged around the second battery cell 62 .
  • the outer battery cells among the plurality of battery cells may be in contact with the inner surface of the battery pack box (upper box 2, lower box 3), or may be in contact with the inner surface of the battery pack.
  • the structural members are in contact with the inner surface of the box.
  • gaps g1 and g2 are optionally formed between the outermost battery cells and the inner surface of the battery pack box.
  • Various components of the battery pack can be set in these gaps g1 and g2. Structure.
  • Capacitors can be optionally provided in the gaps between different battery cells to increase the energy density of the entire battery pack.
  • the highest temperature in the third area is T 2 and the lowest temperature is TL ,
  • the internal area of the battery pack box space can be better divided. This division method enables the battery pack to better adapt to low-temperature environments.
  • low temperature refers to a temperature ⁇ 10°C.
  • Pure lithium iron phosphate has good low-temperature discharge performance, so battery packs containing pure lithium iron phosphate are very suitable for use at low temperatures.
  • Compounds having at least two carbonyl groups and the at least two carbonyl groups are conjugated with the unsaturated atoms, groups or structures connected thereto have excellent electrochemical redox properties within their own applicable voltage range, and are between 1.9 and 1.9 There is a relatively gentle voltage platform between 2.9V. Mixing them in the lithium iron phosphate system in an appropriate amount can slow down the decline of the discharge voltage when the voltage of the battery cell rapidly decays (below 3V) at the end of the discharge process, thus prolonging the discharge process. And improve the discharge power performance of the battery.
  • the discharge capacity of the single cell of the first battery cell is CAP1
  • the discharge capacity of the single cell of the second battery cell is CAP2
  • the discharge capacity of the single cell of the third battery cell is CAP2.
  • the discharge capacity of the battery cell is CAP3, and the discharge capacity of each of the first, second, and third battery cells satisfies the following relationship:
  • the value range of CAP3/CAP2 is 1.005 ⁇ 1.15, and
  • the value range of CAP2/CAP1 is 1.003 ⁇ 1.12.
  • the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship: the value of CAP3/CAP2 ranges from 1.01 to 1.05, and the value of CAP2/CAP1 ranges from 1.01 to 1.05. It is 1.003 ⁇ 1.04. As a result, the discharge energy and total energy retention rate of the battery pack at low temperatures are further improved.
  • the respective constituent units of the first battery cell, the second battery cell, and the third battery cell are called “single battery cells.”
  • the theoretical gram capacity of the compound that can be used as a low temperature additive is in the range of 150-800 mAh/g, optionally in the range of 180-600 mAh/g. Therefore, by using a low-temperature additive with a theoretical gram capacity within the above range, it is possible to ensure that each battery cell has sufficient energy density and improve the low-temperature discharge power of each battery cell and the battery pack as a whole.
  • the gram capacity of the entire cathode active material of the first battery cell is 136-154 mAh/g
  • the gram capacity of the entire cathode active material of the second battery cell is 133-163 mAh/g
  • the overall gram capacity of the positive active material of the third battery cell is 128-172 mAh/g.
  • the first battery cell 61 , the second battery cell 62 and the third battery cell 63 can be made.
  • the discharge capacity of the cell 62 and the third battery cell 63 at low temperatures is approximately the same, which improves the energy retention rate of the entire battery pack 1 at low temperatures.
  • the gram capacity of the positive electrode active material of each battery cell refers to the average gram capacity of the positive electrode active material. For example, it can be calculated based on the respective gram capacities and mass proportions of lithium iron phosphate and low-temperature additives contained in the positive electrode active material. .
  • the relative molecular weight of the compound that can be used as a low temperature auxiliary agent is in the range of 100-800.
  • the low temperature auxiliary agent is selected from simple quinones, substituted quinones, quinones fused with heterocyclic rings, polycarbonyl quinones, cyclic dianhydrides fused with unsaturated rings or cyclic Diimides and their salts, substituted or unsubstituted six-membered rings containing 3 or 4 carbonyl groups and 2 or 3 atoms containing lone pairs of electrons, 2-4 carbonyl groups and 1 - Alkoxides of a six-membered ring with two double bonds and without heterocyclic atoms, and carboxylates containing a benzene ring or double bond, and the benzene ring or double bond is conjugated with at least two carbonyl groups.
  • the simple quinones may be selected from p-benzoquinone, o-benzoquinone, naphthoquinone, anthraquinone, phenanthrenequinone, etc.
  • the substituted quinones may refer to simple quinones or alkoxides of simple quinones substituted by one or more, optionally at least two halogens, alkoxy, or hydroxyl groups, such as at least two chlorine, methoxy, or hydroxyl groups. Substituted simple quinones or lithium oxide salts of simple quinones.
  • the quinones fused with a heterocyclic ring may refer to p-benzoquinone or o-benzoquinone fused with a five-membered unsaturated ring or a six-membered unsaturated ring containing at least one oxygen atom, nitrogen atom or sulfur atom.
  • the polycarbonylquinones may refer to compounds containing 3-15, optionally 5-10 fused unsaturated rings containing at least two benzoquinone structures.
  • the unsaturated ring may be a benzene ring, an unsaturated five- or six-membered heterocyclic ring containing N, O or S, a p-benzoquinone ring, an o-benzoquinone ring, etc.
  • the cyclic dianhydrides or cyclic diimides and their salts fused with an unsaturated ring may refer to compounds and their salts in which the ring contains a dianhydride structure or a diimide structure.
  • a saturated or unsaturated five-membered ring or a six-membered ring is fused with a fused benzene ring such as a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, perylene ring, etc.
  • the salt of the cyclic dianhydride or cyclic diimide condensed with an unsaturated ring may be an alkali metal salt or more preferably a lithium salt.
  • the substituted or unsubstituted six-membered rings containing 3 or 4 carbonyl groups and 2 or 3 atoms containing lone pairs of electrons may refer to unsubstituted or substituted six-membered rings containing 3 carbonyl groups and three options.
  • the The substituents may be halogen, C 1-6 alkyl, C 1-6 alkenyl, phenyl, naphthyl, phenanthrenyl, etc.
  • the halogen is selected from fluorine, chlorine, bromine, iodine, and optionally chlorine.
  • the C 1-6 alkyl group may include, but is not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, iso Pentyl, tert-pentyl, neopentyl, n-hexyl, isohexyl, tert-hexyl, etc.
  • the C 1-6 alkenyl group may include, but is not limited to, vinyl, propenyl, isopropenyl, n-butenyl, isobutenyl, n-pentenyl, isopentenyl, tert-pentene base, n-hexenyl, isohexenyl, tert-hexenyl, etc.
  • the six-membered ring alkoxides containing 2-4 carbonyl groups and containing 1-2 double bonds without heterocyclic atoms may refer to such six-membered rings, which do not contain heterocyclic atoms in the ring and contain 2- 4 carbonyl groups and containing 1-2 double bonds, and the ring also contains at least 2, optionally up to 4 alkali metal oxy groups, optional lithium oxy groups.
  • Carboxylates containing benzene rings or double bonds and the benzene rings or double bonds are conjugated with at least two carbonyl groups may refer to containing at least two carboxylate ester groups and a benzene ring and a benzene ring are connected between the two carboxylate ester groups. /or alkali metal salt of double bond, optional lithium oxide group.
  • the low temperature auxiliary agent is selected from one or more of the following compounds:
  • This compound has two reversible charge and discharge voltage platforms at 2.7-3.0V and 2.3-2.5V during the discharge process, with a theoretical gram capacity of 370mAh/g;
  • R is H, C 1-6 alkyl or C 1-6 alkenyl, optionally propyl, propenyl or phenyl,
  • the theoretical gram capacity of dichloroisocyanuric acid is 406 mAh/g
  • the theoretical gram capacity of piperazine tetraone (PRP) in which R is n-propyl is 237 mAh/g
  • the theoretical gram capacity of piperazine tetraone (AP) in which R is propylene The theoretical gram capacity is 240mAh/g, and the theoretical gram capacity of piperazine tetraketone (PHP) where R is phenyl is 182mAh/g;
  • Lithium terephthalate salt, lithium 2,4-dienyl adipate salt, and lithium vinyl dibenzoate salt which respectively have the following structural formulas:
  • Lithium pyromellitic acid diimide salt and lithium naphthalenetetracarboxylic acid diimide dilithium salt respectively have the following structural formulas:
  • the low-temperature additives described generally or specifically above have a reversible charge and discharge platform. After partially replacing lithium iron phosphate, they can alleviate the attenuation of voltage through the auxiliary effect of the reversible charge and discharge platform when the battery is discharged at low SOC. function, thereby improving the discharge power performance of the battery core.
  • the mass proportion of the low-temperature additive is 0-13%, based on the positive electrode. Total mass of active substances.
  • the mass proportion of the low-temperature additive is greater than 13%, the content may be too high, resulting in excessive lithium supplementation for the corresponding negative electrode, which will increase production safety risks.
  • the mass proportion of the low-temperature additive is 0-2%, based on the total amount of the active material
  • the mass proportion of the low-temperature additive is 2-8%, based on the total amount of the active material
  • the mass proportion of the low-temperature additive is 8-13%, based on the total amount of the active material.
  • the positive electrode of the first battery cell in the first region may not include the low-temperature additive, may include part of the low-temperature additive, or may include all of the low-temperature additive.
  • the first battery cell is placed in the first area of the battery pack where the temperature is high. When running at low temperature, the temperature is higher, and the discharge capacity is also higher. The low temperature performance requirements are lower, so no or a small amount of low temperature additives may be added.
  • the mass proportion of the low-temperature additive is in the range of 2-8%.
  • the discharge voltage platform of the low-temperature additive can alleviate voltage attenuation, thereby increasing the power of the battery pack. performance and low temperature retention.
  • the mass proportion of the low-temperature additive in the first battery cell, the second battery cell and the third battery cell fall within the above range, the first battery cell, the second battery cell can be better balanced.
  • the discharge time of the single cell and the third battery cell is kept as consistent as possible, and can further improve the low-temperature energy retention rate and power performance of the overall battery pack.
  • the discharge cut-off voltages of the first battery cell, the second battery cell, and the third battery cell are the same. In other optional embodiments, the difference between the discharge cut-off voltage of the first battery cell and the second battery cell or the discharge cut-off voltage of the second battery cell and the third battery cell is The difference is less than 0.03V.
  • a second aspect of the present application provides a method for arranging a battery pack.
  • the battery pack includes a battery pack box and battery cells accommodated in the battery pack box.
  • the method includes:
  • Step (1) Determine the temperature distribution in the entire internal space of the battery pack box when used at low temperatures based on the simulation method.
  • Step (2) According to the temperature distribution determined in step (1), divide the internal space of the battery pack box into three regions in order of temperature from high to low.
  • Step (3) Arrange a first battery cell in the first region, a second battery cell in the second region, and a third battery cell in the third region, so that the first battery cell
  • the body and the second battery cell are arranged adjacently, so that the second battery cell and the third battery cell are arranged adjacently,
  • the internal space of the battery pack box includes one or more first areas, second areas and/or third areas;
  • the positive electrodes of the first battery cell, the second battery cell, and the third battery cell each include a positive electrode active material, and the positive electrode active material is composed of the following substances:
  • Low temperature auxiliary agent which is selected from one or more of the following compounds: the compound contains at least two carbonyl groups, and the at least two carbonyl groups are individually or together with a double bond, an unsaturated monocyclic ring or a double bond connected thereto. Unsaturated fused rings, unsaturated groups, conjugated atoms containing lone pairs of electrons,
  • the discharge capacity of the single cell of the first battery cell is CAP1
  • the discharge capacity of the single cell of the second battery cell is CAP2
  • the discharge capacity of the third battery cell is CAP2.
  • the discharge capacity of a single cell is CAP3, and the discharge capacity of each single cell of the first, second, and third battery cells satisfies the following relationship:
  • the range of CAP3/CAP2 is 1.005 ⁇ 1.15, and
  • the range of CAP2/CAP1 is 1.003 ⁇ 1.12.
  • a third aspect of this application provides an electrical device, which includes the battery pack described in the first aspect of this application.
  • the battery pack can be used as a power source for the electrical device or as an energy storage unit for the electrical device.
  • the electric device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, and electric golf carts). , electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but are not limited to these.
  • a battery cell or a battery pack can be selected according to its usage requirements.
  • FIG. 4 is an electrical device as an example.
  • the electric device is a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.
  • the battery pack of the present application can be used.
  • the first cathode active material lithium iron phosphate (LFP) and low temperature additive as the cathode active material, superconducting carbon black SP as the conductive agent and polyvinylidene fluoride (PVDF) as the binder are dispersed in N as the solvent -Methyl pyrrolidone (NMP) and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, and after drying, cold pressing, slitting, and cutting, the positive electrode sheet is obtained.
  • NMP solvent -Methyl pyrrolidone
  • the mass ratio of positive electrode active material, conductive carbon black, and binder PVDF is 96:2:2, and the mass ratio of low-temperature additive to LFP is 5:95.
  • the negative active material graphite, superconducting carbon black SP as the conductive agent, SBR as the binder, and CMC-Na as the thickener are dispersed and mixed in deionized water as the solvent in a mass ratio of 96:1:1:2 Uniformly, the negative electrode slurry is obtained; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; after drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.
  • Negative lithium replenishment process lithium replenishment is performed on the coated and cold-pressed negative electrode pieces through a lithium replenishment device.
  • the lithium belt conveying structure in the device is used to convey the lithium belt
  • the base material conveying structure is used to convey the negative electrode piece.
  • the lithium belt and the negative electrode piece are rolled. After rolling, the lithium belt adheres to the surface of the negative electrode piece, completing the negative electrode pre-replenishment. lithium.
  • ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent. Then dissolve the fully dried lithium salt LiPF 6 in the mixture. In the final organic solvent, prepare an electrolyte solution with a concentration of 1 mol/L.
  • the above-mentioned positive electrode pieces, isolation films, and negative electrode pieces are stacked in sequence so that the isolation film is between the positive electrode pieces and the negative electrode pieces to play an isolation role, and then the bare cells are obtained by winding them; the bare cells are placed in the outer packaging After drying, electrolyte is injected into the shell, and the first battery cell I-1 is obtained through processes such as vacuum packaging, standing, formation, and shaping.
  • ANSYS-SCDM software is used to divide the internal space of the battery pack box into three areas.
  • the specific operations are as follows:
  • the outside temperature is -7°C
  • the highest temperature in the first zone is 18°C
  • the lowest temperature is 12°C
  • the highest temperature in the second zone is 12°C
  • the lowest temperature is 6°C
  • the highest temperature in the third zone is 12°C
  • the lowest temperature is 6°C
  • the highest temperature is 6°C and the lowest temperature is 0°C.
  • the first battery cell I-1 is configured as the first battery cell 61 in the first region R1
  • the second battery cell II-1 is configured as the second battery cell 62 in the second region R2.
  • the third battery cell III-1 is arranged in the third region R3 as the third battery cell 63 and assembled into a battery pack.
  • the overall cut-off voltage of the first battery cell is designed to be 2V
  • the overall cut-off voltage of the second battery cell is designed to be 2V
  • the overall cut-off voltage of the third battery cell is designed to be 2V.
  • the discharge cut-off voltage of the three battery cells is set to 2.5V at a test temperature above 10°C.
  • the first battery cell, the second battery cell and the third battery cell in each battery pack prepared in the examples and comparative examples were measured using a Xinwei power battery testing machine (model BTS-5V300A-4CH).
  • the discharge capacity of the first battery cell, the second battery cell and the third battery cell at -7°C is then calculated to calculate the respective low temperature assist of the first battery cell, the second battery cell and the third battery cell.
  • the method of measuring the discharge capacity of a battery cell is as follows:
  • step (8) Obtain the discharge curve in step (8), for example, such as the discharge curve in Figure 3 of this application.
  • the total discharge capacity before the 2.3V point is the lithium iron phosphate discharge voltage platform.
  • the corresponding discharge capacity C2 the discharge capacity from the 2.3V point to the discharge cut-off voltage is the discharge capacity C3 corresponding to the low-temperature additive discharge voltage platform.
  • the proportion of discharge capacity corresponding to the low-temperature additive discharge voltage platform of the battery cell C3/C1.
  • the single cell discharge capacity in Table 1 below is the total discharge capacity C1 measured by the battery cells at -7°C in step (8).
  • the discharge capacity of each battery cell at 10°C and -20°C is the same as the above-mentioned discharge capacity test at -7°C. During the test, -7°C can be modified accordingly to 10°C and -20°C.
  • a Xinwei power battery testing machine (model BTS-5V300A-4CH) was used to measure the total full discharge energy of the battery pack at 25°C and the total full discharge energy of the battery pack at -7°C.
  • the total full discharge energy of the battery pack at -7°C is divided by the total full discharge energy of the battery pack at 25°C to calculate the total energy retention rate (%) of the battery pack at -7°C.
  • the measurement of the total full discharge energy of the battery pack at -7°C is carried out in accordance with "7.1.4 Capacity and Energy Test at Low Temperature” in "GBT 31467.2-2015 Battery Pack and System High Energy Application Test Procedures".
  • the total full discharge energy of the battery pack at -7°C is the -7°C discharge energy of the battery pack in Table 1 below.
  • Embodiment 1-11 in which the ratio range is 1.003-1.12 and the ratio range of the discharge capacity of the single cell of the third battery cell to the second battery cell is 1.005-1.15 has higher low-temperature discharge energy and total energy Retention rate.
  • Example 1 when the ratio of the discharge capacity of the single cells of the second battery cell to the first battery cell ranges from 1.003 to 1.04 at low temperature, and the ratio of the second battery cell to the first battery cell When the ratio of the discharge capacity of a single cell ranges from 1.01 to 1.05, the battery pack has the highest low-temperature discharge energy and total energy retention rate.

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Abstract

本申请提供了一种电池包，其包括第一、二、三电池单体，各电池单体的正极活性物质由磷酸铁锂和低温助剂组成，所述低温助剂选自含至少两个羰基且所述至少两个羰基与和其连接的不饱和结构或含孤对电子的原子共轭的化合物，在温度≤10℃时，所述第二电池单体与第一电池单体的单电芯的放电容量的比值范围为1.003～1.12，所述第三电池单体与第二电池单体的单电芯的放电容量的比值范围为1.005～1.15。本申请提供的电池包在低温下放电能量和能量保持率更高。

Description

电池包和用电装置 技术领域
本申请涉及锂离子电池领域，尤其涉及一种低温下的能量保持率高的电池包和包括该电池包的用电装置。
背景技术
近年来，随着锂离子电池技术的不断发展，锂离子电池被广泛应用于水力、火力、风力和太阳能电站等储能电源系统，以及电动工具、电动自行车、电动摩托车、电动汽车、军事装备、航空航天等多个领域。
在上述领域中，锂离子二次电池单体的容量有时无法满足使用需求，此时需要将多个锂离子二次电池单体串联或者并联组成电池包以提高电池包的整体放电量。
但是，由锂离子二次电池单体组成的电池包，在冬季那样的低温环境下使用时，能量保持率大幅降低，即，在低温下的续航能力严重缩水，如何提高电池包整体在低温下的续航能力成为亟待解决的关键问题。
发明内容
本申请是鉴于上述技术问题而做出的，其目的在于，提供一种低温下的能量保持率优异、低温下的续航能力提高的由锂离子二次电池组成的电池包和包括该电池包的用电装置。
为了实现上述目的，本申请的第一方面一种电池包，其包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述电池包的特征在于，根据所确定的低温下应用时电池包箱体整个内部空间中的温度分布，所述电池包箱体的内部空间中，按温度由高到低的顺序，包括第一区域、第二区域、第三区域，在所述第一区域中配置有第一电池 单体，在第二区域中配置有第二电池单体，在第三区域中配置有第三电池单体，所述第一电池单体与第二电池单体相邻排布，所述第二电池单体与第三电池单体相邻排布，
电池包箱体的内部空间中包括一个或更多个第一区域、第二区域和/或第三区域；
所述第一电池单体、第二电池单体、第三电池单体各自的正极包括正极活性物质，所述正极活性物质由以下物质组成：
磷酸铁锂，和
低温助剂，其选自以下化合物中的一种或多种：所述化合物含有至少两个羰基，并且所述至少两个羰基各自地或一起与和其连接的双键、不饱和单环或不饱和稠合环、不饱和基团、含有孤对电子的原子共轭，且
在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
CAP3/CAP2的值的范围为1.005～1.15，且
CAP2/CAP1的值的范围为1.003～1.12。
本申请中，可通过仿真方法确定电池包内部空间的温度分布，然后在温度由高至低的方向上将电池包箱体内部空间划分区域。作为一个实例，可使用ANSYS-SCDM软件(北京环中睿驰科技有限公司)通过仿真方法确定电池包内部空间的温度分布，步骤如下：
(1)进行电池低温(≤10℃)工况测试，在此过程中，记录电流大小、电池电阻、工况流程参数，
(2)在ANSYS-SCDM软件中输入电池包三维结构数模、材料导热系数、水冷系统结构、水冷流速、水冷温度，即可计算出电池包内部产热和散热平衡，从而获得不同时间、不同位置的温度分布。
在一些实施方式中，根据确定的低温下应用时电池包箱体整个内部空间中的温度分布，对于第一区域、第二区域或第三区域，同一区域中的最高温度和最低温度之差≥3℃，可选地≤10℃，可选地，第三区 域的最高温度≤第二区域的最低温度，且第二区域的最高温度≤第一区域的最低温度。
当电池包箱体空间中的最高温度和最低温度之差<3℃时，可以不划分区域。基于经验可知，同一区域中3℃以内的温度差值对同一区域中电池放电容量影响不大。
在一些实施方式中，电池包箱体的整个内部空间中，根据确定的低温下应用时电池包箱体的内部空间中的最高温度为T H，最低温度为T L，T H-T L＝T M，
第一区域的最高温度为T H，最低温度T 1＝T H-(T M/3)，
第二区域的最高温度为T 1，最低温度T 2＝T H-2(T M/3)
第三区域的最高温度为T 2，最低温度为T L，
其中3℃≤T M/3≤10℃。
由此，能够更好地划分电池包箱体空间的内部区域，这种划分方式使得电池包能够更好地适应低温环境。
具有至少两个羰基并且所述至少两个羰基与和其相连接的不饱和原子、基团或结构共轭的化合物在自身适用的电压范围内具有优异的电化学氧化还原性质，并且在1.9～2.9V之间具有较为平缓的电压平台，将它们适量混合在磷酸铁锂体系中，能够使电芯在放电过程末端电压急速衰减(3V以下)的时候，减缓放电电压的下降，从而延长放电过程并提高电池的放电功率性能。
在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
CAP3/CAP2的值的范围为1.005～1.15，且
CAP2/CAP1的值的范围为1.003～1.12。
由此，在电池包放电时，可以缩小由于电池包不同区域温升不同导致的电芯放电差异，因而整体上能够提高电池包在低温下的放电能量和总能量保持率。在一些实施方式中，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：CAP3/CAP2的值的范围为 1.01～1.05，且CAP2/CAP1的值的范围为1.003～1.04。由此，电池包在低温下的放电能量和总能量保持率进一步提高。
在一些实施方式中，可作为低温助剂的所述化合物的理论克容量在150-800mAh/g范围内、可选地在180-600mAh/g范围内。由此，通过使用理论克容量在上述范围内的低温助剂，能够确保各电池单体具有足够的能量密度，提高各电池单体和电池包整体的低温放电功率。
在一些实施方式中，所述第一电池单体的正极活性物质整体的克容量为136-154mAh/g，所述第二电池单体的正极活性物质整体的克容量为133-163mAh/g，所述第三电池单体的正极活性物质整体的克容量为128-172mAh/g。由此，通过使第一电池单体、第二电池单体和第三电池单体各自正极活性物质整体的克容量在上述范围内，能够使第一电池单体、第二电池单体和第三电池单体在低温下的放电容量大致一致，提高电池包1整体在低温下的能量保持率。
在一些实施方式中，可作为低温助剂的所述化合物的相对分子量在100-800范围内。
在一些实施方式中，所述低温助剂选自简单醌类、取代的醌类、与杂环稠合的醌类、多羰基醌类、与不饱和环稠合的环状二酐或环状二酰亚胺类及其盐、取代的或未取代的含有3个或4个羰基且含有2个或3个含孤对电子的原子的六元环类、含2-4个羰基且含1-2个双键的不含杂环原子的六元环的醇盐类、含苯环或双键且所述苯环或双键与至少两个羰基共轭的羧酸盐类。可选地，所述低温助剂选自以下化合物中的一种或多种：1,4-二苯醌基苯、对苯醌、邻苯醌、蒽醌、菲醌、2,3,5,6-四氢-1,4-苯醌、2,5-二甲氧基苯醌、1,3,4-三羟基蒽醌、1,5-二锂氧基蒽醌、二吡啶并对苯醌、二吡啶并邻苯醌、二噻吩并对苯醌、二噻吩并邻苯醌、二呋喃并对苯醌、壬苯并六醌、5,7,12,14-并五苯四醌、均苯四甲酸酐、萘四甲酸二酐、苝四甲酸二酐、二氯异氰尿酸、未被取代的或被C 1-6烷基或C 1-6烯基取代的哌嗪四酮衍生物、2,5-二羟基苯醌二锂盐、玫棕酸二锂盐、玫棕酸四锂盐、对苯二甲酸锂盐、2,4-二烯基己二酸锂盐、乙烯基二苯甲酸锂盐、均苯四甲酸二酰亚胺锂盐、萘四甲酸二酰亚胺二锂盐。
上述低温助剂具有可逆的充放电平台，其在部分替代磷酸铁锂后，能够在电池低SOC放电时，通过可逆充放电平台的辅助作用对电压的衰减起到缓解的作用，从而提高了电芯放电功率性能。
在一些实施方式中，在所述第一电池单体、第二电池单体、第三电池单体各自的正极中，所述低温助剂的质量占比为0-13％，基于所述正极活性物质的总质量计。所述低温助剂的质量占比若大于13％，则可能由于含量过高，导致对应的负极补锂量过多，会增加生产安全风险。
在一些可选实施方式中，所述第一电池单体各自的正极中，所述低温助剂的质量占比为0-2％，基于所述活性物质的总量计，所述第二电池单体各自的正极中，所述低温助剂的质量占比为2-8％，基于所述活性物质的总量计，所述第三电池单体各自的正极中，所述低温助剂的质量占比为8-13％，基于所述活性物质的总量计。
由此，通过使第一电池单体、第二电池单体和第三电池单体中的低温助剂的质量占比在上述范围内，能够更好的均衡第一电池单体、第二电池单体、第三电池单体的放电时间，使它们尽可能的保持一致，并且能够进一步提升电池包整体的低温能量保持率和功率性能。
本申请的第二方面提布置电池包的方法，所述电池包包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述方法包括：
步骤(1)：根据仿真方法确定低温下应用时电池包箱体整个内部空间中的温度分布，
步骤(2)：根据步骤(1)确定的温度分布，将所述电池包箱体的内部空间按照温度由高到低的顺序划分3个区域，
步骤(3)：在所述第一区域中配置第一电池单体，在第二区域中配置第二电池单体，在第三区域中配置第三电池单体，使所述第一电池单体与第二电池单体相邻排布，使所述第二电池单体与第三电池单体相邻排布，
电池包箱体的内部空间中包括一个或更多个第一区域、第二区域和/或第三区域；
所述第一电池单体、第二电池单体、第三电池单体各自的正极包括正极活性物质，所述正极活性物质由以下物质组成：
磷酸铁锂，和
低温助剂，其选自以下化合物中的一种或多种：所述化合物含有至少两个羰基，并且所述至少两个羰基各自地或一起与和其连接的双键、不饱和单环或不饱和稠合环、不饱和基团、含有孤对电子的原子共轭，
在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
CAP3/CAP2范围为1.005～1.15，且
CAP2/CAP1范围为1.003～1.12。
用电装置
本申请第三方面提供一种用电装置，所述用电装置包括本申请第一方面所述的电池包。所述电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(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，但不限于此。
作为所述用电装置，可以根据其使用需求来选择电池单体或电池包。
图4是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对低温下的续航能力的需求，可以采用本申请的电池包。
附图说明
图1是本申请一实施方式的电池包的结构示意图。
图2是将电池包箱体的内部空间划分为3个区域的情况下的、图1所示的本申请一实施方式的电池包除去箱体后的结构组件的俯视图。
图3是本申请一实施方式的电池包中使用的具有双放电电压平台的电池单体的恒流放电曲线的示意图，其中，电池单体的正极活性物质由磷酸铁锂(LFP)和对苯醌组成。
图4是使用本申请一实施方式的电池包作为电源的用电装置的示意图。
附图标记说明
1电池包；2上箱体；3下箱体；g1、g2间隙；BL1第一边界线；BL2第二边界线；BL3第三边界线；R1第一区域；R2第二区域；R3第三区域；61第一电池单体；62第二电池单体；63第三电池单体。
具体实施方式
以下，适当地参照附图详细说明具体公开了本申请的电池包和用电装置的实施方式。但是会有省略不必要的详细说明的情况。例如，有省略对已众所周知的事项的详细说明、实际相同结构的重复说明的情况。这是为了避免以下的说明不必要地变得冗长，便于本领域技术人员的理解。此外，附图及以下说明是为了本领域技术人员充分理解本申请而提供的，并不旨在限定权利要求书所记载的主题。
本申请所公开的“范围”以下限和上限的形式来限定，给定范围是通过选定一个下限和一个上限进行限定的，选定的下限和上限限定了特别范围的边界。这种方式进行限定的范围可以是包括端值或不包括端值的，并且可以进行任意地组合，即任何下限可以与任何上限组合形成一个范围。例如，如果针对特定参数列出了60-120和80-110的范围，理解为60-110和80-120的范围也是预料到的。此外，如果列出的最小范围值1和2，和如果列出了最大范围值3，4和5，则下面的范围可全部预料到：1-3、1-4、1-5、2-3、2-4和2-6。在本申请中，除非有其他说明，数值范围“a-b”表示a到b之间的任意实数组合的缩略表示，其中a和b都是实数。例如数值范围“0-5”表示本文中已经全部列 出了“0-5”之间的全部实数，“0-5”只是这些数值组合的缩略表示。另外，当表述某个参数为≥2的整数，则相当于公开了该参数为例如整数2、3、4、5、6、7、8、9、10、11、12等。数值范围“a-b”和“a-b”同义使用。
如果没有特别的说明，本申请的所有实施方式以及可选实施方式可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有技术特征以及可选技术特征可以相互组合形成新的技术方案。
如果没有特别的说明，本申请的所有步骤可以顺序进行，也可以随机进行，优选是顺序进行的。例如，所述方法包括步骤(a)和(b)，表示所述方法可包括顺序进行的步骤(a)和(b)，也可以包括顺序进行的步骤(b)和(a)。例如，所述提到所述方法还可包括步骤(c)，表示步骤(c)可以任意顺序加入到所述方法，例如，所述方法可以包括步骤(a)、(b)和(c)，也可包括步骤(a)、(c)和(b)，也可以包括步骤(c)、(a)和(b)等。
如果没有特别的说明，本申请所提到的“包括”和“包含”表示开放式，也可以是封闭式。例如，所述“包括”和“包含”可以表示还可以包括或包含没有列出的其他组分，也可以仅包括或包含列出的组分。
如果没有特别的说明，在本申请中，术语“或”是包括性的。举例来说，短语“A或B”表示“A，B，或A和B两者”。更具体地，以下任一条件均满足条件“A或B”：A为真(或存在)并且B为假(或不存在)；A为假(或不存在)而B为真(或存在)；或A和B都为真(或存在)。
发明人注意到，由锂离子二次电池单体组成的电池包，在冬季的低温环境下使用时，因电池包中不同位置的电池单体的散热能力和保温效果不同，会导致不同位置的电池单体充放电性能不一致。具体而言，在低温环境下使用时，电池包中位于内侧的电池单体温度相对较高，低温下的放电性能相对较好，电池包中位于外侧的电池单体温度相对较低，低温下的放电性能相对较差。电池包中不同部位的电池单体在低温下放电能力的差异，导致电池包整体在低温下的能量保持率大幅降低。
针对上述问题，发明人反复进行了研究，结果发现，通过使配置在温度较低的区域的电池单体具有较低的放电电压平台能够提高电池包整体的低温下容量保持率。这是因为，在较高的放电电压平台放电结束之后，可以继续利用较低的放电电压平台进行放电，从而使这些电池单体在低温下的放电性能更优异。
因此，本申请的第一方面一种电池包，其包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述电池包的特征在于，
根据所确定的低温下应用时电池包箱体整个内部空间中的温度分布，所述电池包箱体的内部空间中，按温度由高到低的顺序，包括第一区域、第二区域、第三区域，在所述第一区域中配置有第一电池单体，在第二区域中配置有第二电池单体，在第三区域中配置有第三电池单体，所述第一电池单体与第二电池单体相邻排布，所述第二电池单体与第三电池单体相邻排布，
电池包箱体的内部空间中包括一个或更多个第一区域、第二区域和/或第三区域；
所述第一电池单体、第二电池单体、第三电池单体各自的正极包括正极活性物质，所述正极活性物质由以下物质组成：
磷酸铁锂，和
低温助剂，其选自以下化合物中的一种或多种：所述化合物含有至少两个羰基，并且所述至少两个羰基各自地或一起与和其连接的双键、不饱和单环或不饱和稠合环、不饱和基团、含有孤对电子的原子共轭，
在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
CAP3/CAP2的值的范围为1.005～1.15，且
CAP2/CAP1的值的范围为1.003～1.12。
本申请中，可通过仿真方法确定电池包内部空间的温度分布，然后在温度由高至低的方向上将电池包箱体内部空间划分区域。可选地， 电池包箱体内部划分可以为2个区域、3个区域或4个区域，最多为5个区域，最佳为3个区域。本申请中仅对划分3个区域的情况进行详细说明，然而，应理解，划分为2个区域、4个区域、5个区域、甚至6个区域的情况也是可行的，只要满足外面的区域(第n区域)的截止电压小于里面的区域(第n-1区域，n为2-6的自然数)的截止电压，均在本申请构思范围内。
作为一个实例，可使用ANSYS-SCDM软件(北京环中睿驰科技有限公司)通过仿真方法确定电池包内部空间的温度分布，步骤如下：
(1)进行电池低温(≤10℃)工况测试，在此过程中，记录电流大小、电池电阻、工况流程参数，
(2)在ANSYS-SCDM软件中输入电池包三维结构数模、材料导热系数、水冷系统结构、水冷流速、水冷温度，即可计算出电池包内部产热和散热平衡，从而获得不同时间、不同位置的温度分布。
需要说明的是，对于本申请，确定电池包内部空间的温度分布的方法不限于仿真方法。本申请的构思是针对在低温下实际应用时因电池包内部温度分布有差异而导致的位置不同的电池单体的放电有差异并且整体放电量下降而作出的，因此所有能够确定实际应用场景下电池包内部温度分布的方法均在本申请的构思范围内。
可以理解的是，本申请所述的电池包箱体的内部空间中可以包括一个或更多个、可选仅包括一个第一区域、第二区域和/或第三区域。
下面，以电池包箱体的内部空间呈大致矩形形状的情况为例，对本申请第一方面所述的电池包进行具体说明。但是，本申请的电池包并不限于电池包箱体的内部空间呈大致矩形形状的情况。
图1是本申请一实施方式的电池包1的结构示意图。图2是将电池包箱体的内部空间划分为3个区域的情况下的、图1所示的本申请一实施方式的电池包除去箱体后的结构组件的俯视图。
如图1、图2所示，本申请的电池包1包括电池箱和设置于电池箱中的多个电池单体(61、62、63)。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，并形成用于容纳多个电池单体的封闭空间(电池包腔体)。
在将电池包箱体的内部空间划分为3个区域的情况下，如图2所示，电池包箱体的内部空间包括第一区域R1、第二区域R2和第三区域R3，第一区域R1是由第一边界线BL1包围的大致矩形的区域，位于电池包箱体的内部空间的矩形形状的中心部(例如，第一区域R1的矩形形状的长和宽可以分别为电池包箱体的内部空间的矩形形状的长和宽的大致二分之一)，第二区域R2是第一边界线BL1与第三边界线BL3之间的大致环形的区域，第三区域R3是第二边界线BL2与第三边界线BL3之间的大致环形的区域，其中，第一边界线BL1、第二边界线BL2、第三边界线BL3是为了清楚地表示第一区域R1、第二区域R2和第三区域R3而画的虚拟线。
进一步地，在所述第一区域R1中配置有第一电池单体61，在所述第二区域R2中配置有第二电池单体62，在所述第三区域R3中配置有第三电池单体63，所述第二电池单体62包围所述第一电池单体61的周围排布，所述第三电池单体63包围所述第二电池单体62的周围排布。
如图2所示，多个电池单体中位于较外侧的电池单体可以是与电池包箱体(上箱体2、下箱体3)的内表面接触，也可以是与设置在电池包箱体的内表面上的结构件接触。在图2所示的俯视图中，在最外侧的电池单体与电池包箱体的内表面之间任选地形成有间隙g1、g2，在这些间隙g1、g2中可以设置电池包的各种结构件。在不同的电池单体之间的空隙中，可以任选地设置电容器等，以提高电池包整体的能量密度。
在一些实施方式中，根据确定的低温下应用时电池包箱体整个内部空间中的温度分布，对于第一区域、第二区域或第三区域，同一区域中的最高温度和最低温度之差≥3℃，可选地≤10℃，可选地，第三区域的最高温度≤第二区域的最低温度，且第二区域的最高温度≤第一区域的最低温度。
当电池包箱体空间中的最高温度和最低温度之差<3℃时，可以不划分区域。基于经验可知，同一区域中3℃以内的温度差值对同一区域中电池放电容量影响不大。
然而，应理解，虽然本申请限定同一区域中的最高温度和最低温度之差≥3℃，可选地≤10℃，但此方案仅为较佳的选择，同一区域中的最高温度和最低温度之差<3℃或>10℃也在本申请构思范围内。
在一些实施方式中，电池包箱体的整个内部空间中，根据确定的低温下应用时电池包箱体的内部空间中的最高温度为T H，最低温度为T L，T H-T L＝T M，
第一区域的最高温度为T H，最低温度T 1＝T H-(T M/3)，
第二区域的最高温度为T 1，最低温度T 2＝T H-2(T M/3)
第三区域的最高温度为T 2，最低温度为T L，
其中3℃≤T M/3≤10℃。
由此，能够更好地划分电池包箱体空间的内部区域，这种划分方式使得电池包能够更好地适应低温环境。
本申请中，“低温”指≤10℃的温度。
纯磷酸铁锂具有较好的低温放电性能，因此包含纯磷酸铁锂的电池包非常适合在低温下使用。
具有至少两个羰基并且所述至少两个羰基与和其相连接的不饱和原子、基团或结构共轭的化合物在自身适用的电压范围内具有优异的电化学氧化还原性质，并且在1.9～2.9V之间具有较为平缓的电压平台，将它们适量混合在磷酸铁锂体系中，能够使电芯在放电过程末端电压急速衰减(3V以下)的时候，减缓放电电压的下降，从而延长放电过程并提高电池的放电功率性能。
测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
CAP3/CAP2的值的范围为1.005～1.15，且
CAP2/CAP1的值的范围为1.003～1.12。
由此，在电池包放电时，可以缩小由于电池包不同区域温升不同导致的电芯放电差异，因而整体上能够提高电池包在低温下的放电能量和总能量保持率。在一些实施方式中，所述第一、第二、第三电池 单体各自单电芯的放电容量满足以下关系：CAP3/CAP2的值的范围为1.01～1.05，且CAP2/CAP1的值的范围为1.003～1.04。由此，电池包在低温下的放电能量和总能量保持率进一步提高。
本申请中，第一电池单体、第二电池单体、第三电池单体各自的组成单元称作“单电芯”。
各电池单体的单电芯在低温下的放电容量测试参见本文“性能测试”部分。
在一些实施方式中，可作为低温助剂的所述化合物的理论克容量在150-800mAh/g范围内、可选地在180-600mAh/g范围内。由此，通过使用理论克容量在上述范围内的低温助剂，能够确保各电池单体具有足够的能量密度，提高各电池单体和电池包整体的低温放电功率。
在一些实施方式中，所述第一电池单体的正极活性物质整体的克容量为136-154mAh/g，所述第二电池单体的正极活性物质整体的克容量为133-163mAh/g，所述第三电池单体的正极活性物质整体的克容量为128-172mAh/g。
由此，通过使第一电池单体61、第二电池单体62和第三电池单体63各自正极活性物质整体的克容量在上述范围内，能够使第一电池单体61、第二电池单体62和第三电池单体63在低温下的放电容量大致一致，提高电池包1整体在低温下的能量保持率。
其中，各电池单体的正极活性物质的克容量是指正极活性物质的平均克容量，例如可以根据正极活性物质中所含的磷酸铁锂和低温助剂各自的克容量和质量占比来计算。
在一些实施方式中，可作为低温助剂的所述化合物的相对分子量在100-800范围内。
在一些实施方式中，所述低温助剂选自简单醌类、取代的醌类、与杂环稠合的醌类、多羰基醌类、与不饱和环稠合的环状二酐或环状二酰亚胺类及其盐、取代的或未取代的含有3个或4个羰基且含有2个或3个含孤对电子的原子的六元环类、含2-4个羰基且含1-2个双键的不含杂环原子的六元环的醇盐类、含苯环或双键且所述苯环或双键与至少两个羰基共轭的羧酸盐类。
所述简单醌类可选自对苯醌、邻苯醌、萘醌、蒽醌、菲醌等。
所述取代的醌类可指被一个或多个、可选地至少两个卤素、烷氧基、羟基取代的简单醌或简单醌的醇盐，例如被至少两个氯、甲氧基、羟基取代的简单醌或简单醌的锂氧基盐。
所述与杂环稠合的醌类可指与含有至少一个氧原子、氮原子或硫原子的五元不饱和环或六元不饱和环稠合的对苯醌或邻苯醌。
所述多羰基醌类可指含有至少两个苯醌结构的3-15个、可选地5-10个不饱和环稠合的化合物。所述不饱和环可为苯环、含N、O或S的不饱和五元或六元杂环、对苯醌环、邻苯醌环等。
所述与不饱和环稠合的环状二酐或环状二酰亚胺类及其盐可指这样的化合物及其盐，在该化合物中，环中含有二酐结构或二酰亚胺结构的饱和或不饱和的五元环或六元环与例如苯环或萘环、蒽环、菲环、苝环等稠合苯环稠合。所述与不饱和环稠合的环状二酐或环状二酰亚胺类的盐可选碱金属盐、更可选锂盐。
所述取代的或未取代的含有3个或4个羰基且含有2个或3个含孤对电子的原子的六元环类可指未被取代的或取代的含有3个羰基和三个选自N、O、S的杂原子的六元环、未被取代的或取代的含有4个羰基和二个选自N、O、S的杂原子的六元环，在取代的情况下，所述取代基可为卤素、C 1-6烷基、C 1-6烯基、苯基、萘基、菲基等。
本申请中，所述卤素选自氟、氯、溴、碘，可选氯。
本申请中，所述C 1-6烷基可包括，但不限于，甲基、乙基、正丙基、异丙基、正丁基、异丁基、叔丁基、正戊基、异戊基、叔戊基、新戊基、正己基、异己基、叔己基等。
本申请中，所述C 1-6烯基可包括，但不限于，乙烯基、丙烯基、异丙烯基、正丁烯基、异丁烯基、正戊烯基、异戊烯基、叔戊烯基、正己烯基、异己烯基、叔己烯基等。
所述含2-4个羰基且含1-2个双键的不含杂环原子的六元环的醇盐类可指这样的六元环，其环中不含杂环原子，含有2-4个羰基且含有1-2个双键，并且该环上还含有至少2个、可选地至多4个碱金属氧基、可选锂氧基。
含苯环或双键且所述苯环或双键与至少两个羰基共轭的羧酸盐类可指含有至少两个羧酸酯基且两个羧酸酯基之间连接有苯环和/或双键的碱金属盐、可选锂氧基。
可选地，所述低温助剂选自以下化合物中的一种或多种：
(1)1,4-二苯醌基苯，其结构式如下：
Figure PCTCN2022108604-appb-000001
该化合物在放电过程中在2.7-3.0V和2.3-2.5V处具有两个可逆的充放电电压平台，理论克容量为370mAh/g；
(2)苯醌、蒽醌、菲醌，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000002
并且分别具有496mAh/g、257mAh/g和257mAh/g的理论克容量；
(3)2,3,5,6-四氯-1,4-苯醌、2,5-二甲氧基苯醌、1,3,4-三羟基蒽醌、1,5-二锂氧基蒽醌，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000003
并且分别具有218mAh/g、257mAh/g、257mAh/g和212mAh/g的理论克容量；
(4)二吡啶并对苯醌、二吡啶并邻苯醌、二噻吩并对苯醌、二噻吩并邻苯醌、二呋喃并对苯醌，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000004
并且分别具有255mAh/g、255mAh/g、244mAh/g、244mAh/g和285mAh/g的理论克容量；
(5)壬苯并六醌、5,7,12,14-并五苯四醌，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000005
并且分别具有488mAh/g和317mAh/g的理论克容量；
(6)均苯四甲酸酐、萘四甲酸二酐、苝四甲酸二酐，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000006
并且分别具有246mAh/g、200mAh/g和137mAh/g的理论克容量；
(7)二氯异氰尿酸、未被取代的或被C 1-6烷基或C 1-6烯基取代的哌嗪四酮衍生物，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000007
其中R为H、C 1-6烷基或C 1-6烯基，可选地为丙基、丙烯基或苯基，
并且，二氯异氰尿酸的理论克容量为406mAh/g，R为正丙基的哌嗪四酮(PRP)的理论克容量为237mAh/g，R为丙烯的哌嗪四酮(AP)的理论克容量为240mAh/g，R为苯基的哌嗪四酮(PHP)的理论克容量为182mAh/g；
(8)2,5-二羟基苯醌二锂盐、玫棕酸二锂盐、玫棕酸四锂盐，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000008
并且分别具有353mAh/g、589mAh/g和274mAh/g的理论克容量；
(9)对苯二甲酸锂盐、2,4-二烯基己二酸锂盐、乙烯基二苯甲酸锂盐，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000009
并且分别具有301mAh/g、348mAh/g和191mAh/g的理论克容量；
(10)均苯四甲酸二酰亚胺锂盐、萘四甲酸二酰亚胺二锂盐，其分别具有以下结构式：
Figure PCTCN2022108604-appb-000010
并且分别具有235mAh/g和193mAh/g的理论克容量。
上述概括地或具体地描述的低温助剂具有可逆的充放电平台，其在部分替代磷酸铁锂后，能够在电池低SOC放电时，通过可逆充放电平台的辅助作用对电压的衰减起到缓解的作用，从而提高了电芯放电功率性能。
在一些实施方式中，在所述第一电池单体、第二电池单体、第三电池单体各自的正极中，所述低温助剂的质量占比为0-13％，基于所述正极活性物质的总质量计。
所述低温助剂的质量占比若大于13％，则可能由于含量过高，导致对应的负极补锂量过多，会增加生产安全风险。
在一些可选实施方式中，所述第一电池单体各自的正极中，所述低温助剂的质量占比为0-2％，基于所述活性物质的总量计，
所述第二电池单体各自的正极中，所述低温助剂的质量占比为2-8％，基于所述活性物质的总量计，
所述第三电池单体各自的正极中，所述低温助剂的质量占比为8-13％，基于所述活性物质的总量计。
本申请中，所述第一区域的第一电池单体的正极中可以均不包括所述低温助剂，也可以部分包括所述低温助剂，还可以全部包括所述低温助剂。可选地，越靠近第二区域，第一电池单体的正极中的低温助剂质量占比越高。
第一电池单体置于电池包的温度高的第一区域，低温下运行时，温度较高，其放电量也较高，对低温性能要求较低，因此可不添加或添加少量低温助剂。
所述第二电池单体中，所述低温助剂的质量占比在2-8％范围内，所述低温助剂的放电电压平台能够起到缓解电压衰减的作用，从而提高电池包的功率性能和低温保持率。
由此，通过使第一电池单体、第二电池单体和第三电池单体中的低温助剂的质量占比在上述范围内，能够更好的均衡第一电池单体、第二电池单体、第三电池单体的放电时间，使它们尽可能的保持一致，并且能够进一步提升电池包整体的低温能量保持率和功率性能。
在一些可选实施方式中，所述第一电池单体、第二电池单体、第三电池单体的放电截止电压相同。在另一些可选实施方式中，所述第一电池单体与第二电池单体的放电截止电压之间的或所述第二电池单体与第三电池单体的放电截止电压之间的差值小于0.03V。
本申请的第二方面提供布置电池包的方法，所述电池包包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述方法包括：
步骤(1)：根据仿真方法确定低温下应用时电池包箱体整个内部空间中的温度分布，
步骤(2)：根据步骤(1)确定的温度分布，将所述电池包箱体的内部空间按照温度由高到低的顺序划分3个区域，
步骤(3)：在所述第一区域中配置第一电池单体，在第二区域中配置第二电池单体，在第三区域中配置第三电池单体，使所述第一电 池单体与第二电池单体相邻排布，使所述第二电池单体与第三电池单体相邻排布，
电池包箱体的内部空间中包括一个或更多个第一区域、第二区域和/或第三区域；
所述第一电池单体、第二电池单体、第三电池单体各自的正极包括正极活性物质，所述正极活性物质由以下物质组成：
磷酸铁锂，和
低温助剂，其选自以下化合物中的一种或多种：所述化合物含有至少两个羰基，并且所述至少两个羰基各自地或一起与和其连接的双键、不饱和单环或不饱和稠合环、不饱和基团、含有孤对电子的原子共轭，
在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
CAP3/CAP2范围为1.005～1.15，且
CAP2/CAP1范围为1.003～1.12。
用电装置
本申请第三方面提供一种用电装置，所述用电装置包括本申请第一方面所述的电池包。所述电池包可以用作所述用电装置的电源，也可以用作所述用电装置的能量存储单元。所述用电装置可以包括移动设备(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，但不限于此。
作为所述用电装置，可以根据其使用需求来选择电池单体或电池包。
图4是作为一个示例的用电装置。该用电装置为纯电动车、混合动力电动车、或插电式混合动力电动车等。为了满足该用电装置对低温下的续航能力的需求，可以采用本申请的电池包。
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。
【实施例1】
I.电池单体的制备
1.第一电池单体的制备
1)正极极片的制备
将作为正极活性物质的第一正极活性物质磷酸铁锂(LFP)和低温助剂、作为导电剂的超导电炭黑SP和作为粘结剂的聚偏氟乙烯(PVDF)分散在作为溶剂的N-甲基吡咯烷酮(NMP)中混合均匀，得到正极浆料；将正极浆料均匀涂覆在正极集流体铝箔上，经烘干、冷压、分条、裁片后，得到正极极片。
其中，正极活性物质、导电炭黑、粘结剂PVDF的质量比为96:2:2，低温助剂与LFP的质量比为5:95。
2)负极极片的制备
将负极活性材料石墨、作为导电剂的超导电炭黑SP、作为粘结剂的SBR和作为增稠剂的CMC-Na按照质量比96:1:1:2分散在作为溶剂的去离子水中混合均匀，得到负极浆料；将负极浆料均匀涂覆在负极集流体铜箔上；经烘干、冷压、分条、裁片后，得到负极极片。
负极补锂过程：通过补锂装置给已涂布冷压后的负极极片进行补锂。装置中锂带输送结构用于输送锂带，基材输送结构用于输送负极极片，将锂带和负极极片进行辊压，辊压后锂带附着于负极极片表面，完成负极预补锂。
3)隔离膜
选用聚乙烯膜作为隔离膜。
4)电解液的制备
将碳酸亚乙酯(EC)、碳酸二甲酯(DMC)、碳酸二乙酯(DEC)按照体积比1:1:1混合均匀得到有机溶剂，接着将充分干燥的锂盐LiPF 6溶解于混合后的有机溶剂中，配制成浓度为1mol/L的电解液。
5)电池单体的制备
将上述正极极片、隔离膜、负极极片按顺序层叠，使隔离膜处于正极极片与负极极片之间起到隔离作用，然后卷绕得到裸电芯；将裸电芯置于外包装壳中，干燥后注入电解液，经过真空封装、静置、化成、整形等工序，获得第一电池单体I-1。
2.第二、第三电池单体的制备
与第一电池单体制备同样地操作，不同之处参见表1。
II.电池包的组装
根据仿真方法，使用ANSYS-SCDM软件，将电池包箱体的内部空间划分3个区域，具体操作如下：
(1)进行电池低温工况测试，在此过程中，记录电流大小、电池电阻、工况流程参数，
(2)在ANSYS-SCDM软件中输入电池包三维结构数模、材料导热系数、水冷系统结构、水冷流速、水冷温度，即可计算出电池包内部产热和散热平衡，从而获得不同时间、不同位置的温度分布。
通过上述方法确定，设定外界温度为-7℃，第一区域的最高温度为18℃，最低温度为12℃，第二区域的最高温度为12℃，最低温度为6℃，第三区域的最高温度为6℃，最低温度为0℃。
参考图2，在第一区域R1中配置第一电池单体I-1作为第一电池单体61，在第二区域R2中配置第二电池单体II-1作为第二电池单体62，在第三区域R3中配置第三电池单体III-1作为第三电池单体63，组装成电池包。其中，第一电池单体61的数量:第二电池单体62的数量:第三电池单体63的数量＝12:32:40。
10℃以下，第一电池单体整体的截止电压设计为2V，第二电池单体整体的截止电压设计为2V，第三电池单体整体的截止电压设计为2V。
用于测试时，在10℃以上的测试温度下，三个电池单体的放电截止电压均设定为2.5V。
【实施例2-13】和【对比例1-2】
与实施例1同样地操作，不同之处参见表1。
【性能测试】
1.各电池单体单电芯在10℃、-7℃、-20℃下的放电容量
对实施例、对比例中制备的各电池包中的第一电池单体、第二电池单体和第三电池单体，分别使用新威动力电池测试机(型号BTS-5V300A-4CH)测量第一电池单体、第二电池单体和第三电池单体各自的-7℃时的放电容量，进而计算出第一电池单体、第二电池单体和第三电池单体各自的低温助剂放电电压平台对应的放电容量占比。
电池单体的放电容量的测量方法如下：
(1)将电池单体在25℃静置2h，确保电池单体的温度为25℃；
(2)在25℃下以0.33C将电池单体充电至3.65V后，继续以该电压进行恒压充电，直至电流为0.05C，充电截止(其中，C表示电池单体额定容量)；
(3)将电池单体在25℃静置1h；
(4)在25℃下以0.33C将电池单体放电至2.5V，记录电池单体放出的总放电容量C0；
(5)将电池单体在25℃静置2h，确保电池单体的温度为25℃；
(6)在25℃下以0.33C将电池单体充电至3.65V后，继续以该电压进行恒压充电，直至电流为0.05C，充电截止(其中，C表示电池单体额定容量)；
(7)将电池单体在-7℃下静置2h；
(8)在-7℃下以0.33C将电池单体放电至2.0V，记录电池单体放出的放电容量C1；
(9)得出步骤(8)中的放电曲线，例如，如本申请的图3中的放电曲线，在图3的放电曲线中，2.3V点前的放电容量合计为磷酸铁锂放电电压平台对应的放电容量C2，2.3V点至放电截止电压的放电容量为低温助剂放电电压平台对应的放电容量C3。
因此，在-7℃时，电池单体的低温助剂放电电压平台对应的放电容量占比＝C3/C1。
下表1中的单电芯放电容量为步骤(8)中-7℃下测量的电池单体放出的总放电容量C1。
各电池单体单电芯在10℃、-20℃下的放电容量与上述-7℃下的放电容量的测试相同，测试时将-7℃相应地修改为10℃、-20℃即可。
2.电池包放电能量(-7℃)和电池包-7℃总能量保持率
电池包-7℃总能量保持率
对各实施例和对比例的各电池包，分别使用新威动力电池测试机(型号BTS-5V300A-4CH)测量电池包25℃总满放能量和电池包-7℃总满放能量，用电池包-7℃总满放能量除以电池包25℃总满放能量，计算出电池包-7℃总能量保持率(％)。
电池包25℃总满放能量的测量按照《GBT 31467.2-2015电池包及系统高能量应用测试规程》中的“7.1.2室温下的容量和能量测试”进行。
电池包-7℃总满放能量的测量按照《GBT 31467.2-2015电池包及系统高能量应用测试规程》中的“7.1.4低温下的容量和能量测试”进行。电池包-7℃总满放能量即为下表1中的电池包-7℃放电能量。
测试结果参见下表。
Figure PCTCN2022108604-appb-000011
Figure PCTCN2022108604-appb-000012
Figure PCTCN2022108604-appb-000013
根据表1的结果可知，与对比例1相比，采用本申请的低温助剂的实施例1-11和对比例2的电池包具有更高的低温放电能量和总能量保持率。
与对比例1-2相比，采用本申请的策略划分温度区域并在不同区域中放置不同的电池单体以使低温下第二电池单体与第一电池单体的单电芯的放电容量的比值范围为1.003～1.12且第三电池单体与第二电池单体的单电芯的放电容量的比值范围为1.005～1.15的实施例1-11，具有更高的低温放电能量和总能量保持率。
由实施例1可知，当低温下所述第二电池单体与第一电池单体的单电芯的放电容量的比值范围为1.003～1.04且所述第二电池单体与第一电池单体的单电芯的放电容量的比值范围为1.01～1.05时，电池包具有最高的低温放电能量和总能量保持率。
由表2可知，与对比例1相比，采用本申请的策略划分温度区域并在不同区域中放置含本申请所述的含至少两个共轭羰基的化合物作为低温助剂的电池包，在10℃、-7℃、-20℃均能确保第二电池单体与第一电池单体的单电芯的放电容量的比值在1.003～1.12范围内且第三电池单体与第二电池单体的单电芯的放电容量的比值在1.005～1.15范围内，且能够实现更好的电池包放电能量和总能量保持率。
需要说明的是，本申请不限定于上述实施方式。上述实施方式仅为示例，在本申请的技术方案范围内具有与技术思想实质相同的构成、发挥相同作用效果的实施方式均包含在本申请的技术范围内。此外，在不脱离本申请主旨的范围内，对实施方式施加本领域技术人员能够想到的各种变形、将实施方式中的一部分构成要素加以组合而构筑的其它方式也包含在本申请的范围内。

Claims (11)

  1. 一种电池包，其包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述电池包的特征在于，
    根据所确定的低温下应用时电池包箱体整个内部空间中的温度分布，所述电池包箱体的内部空间中，按温度由高到低的顺序，包括第一区域、第二区域、第三区域，
    在所述第一区域中配置有第一电池单体，在第二区域中配置有第二电池单体，在第三区域中配置有第三电池单体，所述第一电池单体与第二电池单体相邻排布，所述第二电池单体与第三电池单体相邻排布，
    电池包箱体的内部空间中包括一个或更多个第一区域、第二区域和/或第三区域；
    所述第一电池单体、第二电池单体、第三电池单体各自的正极包括正极活性物质，所述正极活性物质由以下物质组成：
    磷酸铁锂，和
    低温助剂，其选自以下化合物中的一种或多种：所述化合物含有至少两个羰基，并且所述至少两个羰基各自地或一起与和其连接的双键、不饱和单环或不饱和稠合环、不饱和基团、含有孤对电子的原子共轭，
    在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
    CAP3/CAP2的值的范围为1.005～1.15，且
    CAP2/CAP1的值的范围为1.003～1.12。
  2. 根据权利要求1所述的电池包，其特征在于，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
    CAP3/CAP2的值的范围为1.01～1.05，且
    CAP2/CAP1的值的范围为1.003～1.04。
  3. 根据权利要求1或2所述的电池包，其特征在于，所述化合物的理论克容量在150-800mAh/g范围内、可选地在180-600mAh/g范围内。
  4. 根据权利要求1-3中任一项所述的电池包，其特征在于，所述化合物的相对分子量在100-800范围内。
  5. 根据权利要求1-4中任一项所述的电池包，其特征在于，
    所述第一电池单体的正极活性物质整体的克容量为136-154mAh/g，所述第二电池单体的正极活性物质整体的克容量为133-163mAh/g，所述第三电池单体的正极活性物质整体的克容量为128-172mAh/g。
  6. 根据权利要求1-5中任一项所述的电池包，其特征在于，
    所述低温助剂选自简单醌类、取代的醌类、与杂环稠合的醌类、多羰基醌类、与不饱和环稠合的环状二酐或环状二酰亚胺类及其盐、取代的或未取代的含有3个或4个羰基且含有2个或3个含孤对电子的原子的六元环类、含2-4个羰基且含1-2个双键的不含杂环原子的六元环的醇盐类、含苯环或双键且所述苯环或双键与至少两个羰基共轭的羧酸盐类，可选地，所述低温助剂选自以下化合物中的一种或多种：
    1,4-二苯醌基苯、对苯醌、邻苯醌、蒽醌、菲醌、2,3,5,6-四氢-1,4-苯醌、2,5-二甲氧基苯醌、1,3,4-三羟基蒽醌、1,5-二锂氧基蒽醌、二吡啶并对苯醌、二吡啶并邻苯醌、二噻吩并对苯醌、二噻吩并邻苯醌、二呋喃并对苯醌、壬苯并六醌、5,7,12,14-并五苯四醌、均苯四甲酸酐、萘四甲酸二酐、苝四甲酸二酐、二氯异氰尿酸、未被取代的或被C 1-6烷基或C 1-6烯基取代的哌嗪四酮衍生物、2,5-二羟基苯醌二锂盐、玫棕酸二锂盐、玫棕酸四锂盐、对苯二甲酸锂盐、2,4-二烯基己二酸锂盐、乙烯基二苯甲酸锂盐、均苯四甲酸二酰亚胺锂盐、萘四甲酸二酰亚胺二锂盐。
  7. 根据权利要求1-6中任一项所述的电池包，其特征在于，根据确定的低温下应用时电池包箱体整个内部空间中的温度分布，对于第一区域、第二区域或第三区域，同一区域中的最高温度和最低温度之差≥3℃，可选地≤10℃，可选地，第三区域的最高温度≤第二区域的最低温度，且第二区域的最高温度≤第一区域的最低温度。
  8. 根据权利要求1-7中任一项所述的电池包，其特征在于，电池包箱体的整个内部空间中，根据确定的低温下应用时电池包箱体的内部空间中的最高温度为T H，最低温度为T L，T H-T L＝T M，
    第一区域的最高温度为T H，最低温度T 1＝T H-(T M/3)，
    第二区域的最高温度为T 1，最低温度T 2＝T H-2(T M/3)
    第三区域的最高温度为T 2，最低温度为T L，
    其中3℃≤T M/3≤10℃。
  9. 根据权利要求1-8中任一项所述的电池包，其特征在于，
    所述第一电池单体各自的正极中，所述低温助剂的质量占比为0-2％，基于所述活性物质的总量计，
    所述第二电池单体各自的正极中，所述低温助剂的质量占比为2-8％，基于所述活性物质的总量计，
    所述第三电池单体各自的正极中，所述低温助剂的质量占比为8-13％，基于所述活性物质的总量计。
  10. 布置电池包的方法，所述电池包包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述方法包括：
    步骤(1)：根据仿真方法确定低温下应用时电池包箱体整个内部空间中的温度分布，
    步骤(2)：根据步骤(1)确定的温度分布，将所述电池包箱体的内部空间按照温度由高到低的顺序划分3个区域，
    步骤(3)：在所述第一区域中配置第一电池单体，在第二区域中配置第二电池单体，在第三区域中配置第三电池单体，使所述第一电池单体与第二电池单体相邻排布，使所述第二电池单体与第三电池单体相邻排布，
    电池包箱体的内部空间中包括一个或更多个第一区域、第二区域和/或第三区域；
    所述第一电池单体、第二电池单体、第三电池单体各自的正极包括正极活性物质，所述正极活性物质由以下物质组成：
    磷酸铁锂，和
    低温助剂，其选自以下化合物中的一种或多种：所述化合物含有至少两个羰基，并且所述至少两个羰基各自地或一起与和其连接的双键、不饱和单环或不饱和稠合环、不饱和基团、含有孤对电子的原子共轭，
    在测试温度≤10℃时，所述第一电池单体的单电芯的放电容量为
    CAP1，所述第二电池单体的单电芯的放电容量为CAP2，所述第三电池单体的单电芯的放电容量为CAP3，所述第一、第二、第三电池单体各自单电芯的放电容量满足以下关系：
    CAP3/CAP2范围为1.005～1.15，且
    CAP2/CAP1范围为1.003～1.12。
  11. 一种用电装置，其特征在于，包括权利要求1-9中任一项所述的电池包或根据权利要求10所述的方法布置得到的电池包。
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CN111446488A (zh) * 2020-04-30 2020-07-24 宁德时代新能源科技股份有限公司 一种二次电池及其装置
CN113013489A (zh) * 2021-02-25 2021-06-22 珠海冠宇电池股份有限公司 一种电解液及包括该电解液的锂离子电池

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