WO2023230978A1 - 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
WO2023230978A1
WO2023230978A1 PCT/CN2022/096790 CN2022096790W WO2023230978A1 WO 2023230978 A1 WO2023230978 A1 WO 2023230978A1 CN 2022096790 W CN2022096790 W CN 2022096790W WO 2023230978 A1 WO2023230978 A1 WO 2023230978A1
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WIPO (PCT)
Prior art keywords
battery cell
battery
discharge voltage
discharge
voltage platform
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PCT/CN2022/096790
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English (en)
French (fr)
Inventor
朱畅
欧阳少聪
许宝云
谢庭祯
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宁德时代新能源科技股份有限公司
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Priority to EP22936050.8A priority Critical patent/EP4307417A1/en
Priority to PCT/CN2022/096790 priority patent/WO2023230978A1/zh
Priority to JP2024500338A priority patent/JP2024526654A/ja
Priority to CN202280061178.XA priority patent/CN117941115A/zh
Priority to KR1020247004269A priority patent/KR20240022668A/ko
Priority to US18/383,542 priority patent/US12002960B2/en
Publication of WO2023230978A1 publication Critical patent/WO2023230978A1/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
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/4207—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells for several batteries or cells simultaneously or sequentially
    • 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
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • 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
    • H01M10/04—Construction or manufacture in general
    • 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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
    • H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
    • 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
    • H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
    • H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
    • H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
    • 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
    • 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
    • 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
    • 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
    • H01M50/267—Mountings; Secondary casings or frames; Racks, modules or packs; Suspension devices; Shock absorbers; Transport or carrying devices; Holders having means for adapting to batteries or cells of different types or different sizes
    • 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
    • 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 provides a battery pack, which includes a battery pack box and battery cells accommodated in the battery pack box.
  • the internal space of the battery pack box includes a third A region, a second region, and a third region, the first region is configured with a first battery cell, the second region is configured with a second battery cell, and the third region is configured with a
  • the third battery cell is arranged around the first battery cell.
  • the third battery cell is arranged around the second battery cell.
  • the first battery cell is arranged around the second battery cell.
  • the battery cell, the second battery cell and the third battery cell each have a first discharge voltage platform and a second discharge voltage platform, and the average discharge voltage of the first discharge voltage platform is higher than the second discharge voltage platform.
  • the average discharge voltage of the discharge voltage platform, the positive active material of each of the first battery cell, the second battery cell and the third battery cell is composed of the first positive electrode active material having the first discharge voltage platform
  • the substance is mixed with a positive electrode functional additive having the second discharge voltage platform.
  • the positive electrode functional additive is titanium oxide, niobium oxide or titanium niobium oxide.
  • the third battery cell In the first battery cell, the In each of the second battery cell and the third battery cell, when the sum of the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform is 100%, the third battery cell The proportion of discharge capacity corresponding to the second discharge voltage platform of the three battery cells > the proportion of discharge capacity corresponding to the second discharge voltage platform of the second battery cell > the proportion of discharge capacity of the first battery cell The proportion of discharge capacity corresponding to the second discharge voltage platform.
  • the present application improves the energy retention rate of the entire battery pack at low temperatures by arranging battery cells with different discharge capabilities at low temperatures according to the temperature distribution in the battery pack.
  • low-temperature batteries with dual discharge voltage platforms a first discharge voltage platform with a higher discharge voltage and a second discharge voltage platform with a lower discharge voltage
  • Battery cells with different energy retention rates are used, and battery cells with higher low-temperature energy retention rates are placed in areas with lower temperatures.
  • Configuring battery cells with relatively high low-temperature performance (relatively large low-temperature energy retention rate) in low-temperature areas can make the cycle consistency of battery cells in various areas of the battery pack with different temperatures higher, and improve the overall performance of the battery pack. Low-temperature energy retention rate, thus improving the overall low-temperature endurance of the battery pack.
  • the cathode active material of the battery cell with dual discharge voltage platforms in this application is prepared by mixing a conventional cathode active material (first cathode active material) and a cathode functional additive.
  • the conventional cathode active material has the first cathode active material with a higher discharge voltage.
  • the positive electrode functional additive is titanium oxide, niobium oxide or titanium niobium oxide. These positive electrode functional additives have a second discharge voltage platform with a lower discharge voltage. The discharge capacity of the second discharge voltage platform with a lower discharge voltage in the battery cell can be adjusted by changing the content of the positive electrode functional additive in the positive electrode active material.
  • the shape of the battery pack described in this application is arbitrary and can be any shape designed according to customer requirements.
  • the internal space of the battery pack box is not limited to being divided into the above-mentioned three regions, as long as it includes the above-mentioned first region, second region and third region.
  • the internal space of the battery pack box may be composed of the above-mentioned first area, the second area, and the third area; or the internal space of the battery pack box may be composed of the above-mentioned first area, second area
  • there is one or more areas outside the third area as long as the battery cells arranged in the outer area surround the battery cells arranged in the inner area.
  • the internal space of the battery pack box includes more than three areas as mentioned above, as long as the discharge corresponding to the second discharge voltage platform of the battery cell in the outer area is satisfied,
  • the higher the capacity ratio that is, the higher the mass ratio of the positive electrode functional additive in the positive electrode active material of the battery cell.
  • the four corners of the rectangular shape may be used as the outermost area.
  • the second discharge voltage of the battery cell is The platform corresponds to the highest proportion of discharge capacity (that is, the mass proportion of the cathode functional additive in the positive active material of the battery cell is the highest).
  • the internal space of the battery pack box is composed of the first area, the second area and the third area.
  • the above-mentioned excellent effects can be obtained in a battery pack in which the internal space of the battery pack case is divided into the above-mentioned three regions: the first region, the second region, and the third region.
  • the positive electrode functional additive is titanium niobium oxide represented by Ti 2 Nb 2x O 4+5x , where x is an integer above 1.
  • the titanium niobium oxide is selected from One or more of Ti 2 Nb 2 O 9 , TiNb 2 O 7 , Ti 2 Nb 10 O 29 and TiNb 24 O 62 .
  • titanium niobium oxide with excellent performance as a positive electrode functional additive, a battery cell with a suitable second discharge voltage platform can be obtained, thereby realizing a battery pack of the present application with excellent low-temperature performance.
  • the discharge voltage range of the second discharge voltage platform is 1.0-2.0V.
  • the discharge capacity of the second discharge voltage platform at 1.2-1.6V accounts for the second discharge voltage platform. More than 50% of the total discharge capacity, optionally more than 70%.
  • the discharge voltage of the second discharge voltage platform can be significantly different from the discharge voltage of the first discharge voltage platform, and a dual discharge voltage platform can be significantly obtained. the above-mentioned effects.
  • the ratio of the discharge capacity of the second discharge voltage platform at 1.2-1.6V to the total discharge capacity of the second discharge voltage platform within the above range, it can be ensured that the battery cells can release sufficient energy at low temperatures, thereby ensuring that the battery Including the overall low temperature energy retention rate.
  • the difference between the lowest discharge voltage of the first discharge voltage platform and the highest discharge voltage of the second discharge voltage platform is 0.5V. above, optional 1.0V or above.
  • the first discharge voltage platform with a higher discharge voltage can be used for discharge, and then the second discharge voltage platform with a lower discharge voltage can be used for discharge, which can significantly increase the energy that each battery cell can release at low temperatures, thus Improve the overall energy retention rate of the battery pack at low temperatures.
  • the discharge capacity corresponding to the first discharge voltage platform when the sum of the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform is 100%, the The discharge capacity corresponding to one discharge voltage platform accounts for 90%-100%, and the discharge capacity corresponding to the second discharge voltage platform accounts for 0%-10%.
  • the performance of the first battery cell at low temperature can be improved.
  • the energy that can be released thereby improves the overall low-temperature energy retention rate of the battery pack.
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 73%-95%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 5%-27%.
  • the performance of the second battery cell at low temperature can be improved.
  • the energy that can be released further improves the overall low-temperature energy retention rate of the battery pack.
  • the third battery cell when the sum of the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform is 100%, the third battery cell
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 54%-87%, and the discharge capacity corresponding to the second discharge voltage platform accounts for 13%-46%.
  • the proportions of the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform in the third battery cell can be within the above range, the performance of the third battery cell at low temperature can be improved.
  • the energy that can be released further improves the overall low-temperature energy retention rate of the battery pack.
  • the gram capacity of the positive active material of the first battery unit is 148-285 mAh/g
  • the gram capacity of the positive active material of the second battery unit is 155-295 mAh/g
  • the The gram capacity of the positive active material of the third battery cell is 169-311 mAh/g.
  • the theoretical gram capacity of the positive electrode functional assistant is 350-410 mAh/g.
  • the first positive electrode active material is one selected from the group consisting of lithium manganate, lithium nickelate, lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, and lithium iron phosphate.
  • the first cathode active material can be used from now on.
  • the battery pack of the present application can be easily realized using existing cathode active materials.
  • the mass proportion of the first cathode active material to the cathode active material decreases in the order of the first battery cell, the second battery cell, and the third battery cell, and the cathode functional additive
  • the mass proportion of the positive active material increases in the order of the first battery cell, the second battery cell, and the third battery cell.
  • the mass of the first cathode active material accounts for 96.0 %-100%
  • the mass of the positive electrode functional additive accounts for 0%-4.0%.
  • the mass ratio of the first cathode active material and the cathode functional additive in the first battery cell within the above range, the discharge capacity corresponding to the first discharge voltage plateau in the first battery cell and the The respective proportions of the discharge capacity corresponding to the second discharge voltage platform are within the above range, which can increase the energy that the first battery cell can release at low temperatures, thereby improving the low-temperature energy retention rate of the overall battery pack.
  • the mass of the first cathode active material accounts for 88.5% %-96.0%
  • the mass of the positive electrode functional additive accounts for 4.0%-11.5%.
  • the mass ratio of the first positive electrode active material and the positive electrode functional additive in the second battery cell is within the above range, the discharge capacity corresponding to the first discharge voltage plateau in the second battery cell and the The respective proportions of the discharge capacity corresponding to the second discharge voltage platform are within the above range, which can increase the energy that the second battery cell can release at low temperatures, thereby further improving the low-temperature energy retention rate of the overall battery pack.
  • the mass of the first cathode active material accounts for 76.5% %-88.5%
  • the mass of the positive electrode functional additive accounts for 11.5%-23.5%.
  • the mass ratio of the first cathode active material and the cathode functional additive in the third battery cell is within the above range, the discharge capacity corresponding to the first discharge voltage plateau in the third battery cell and the The respective proportions of the discharge capacity corresponding to the second discharge voltage platform are within the above range, which can increase the energy that the third battery cell can release at low temperatures, thereby further improving the low-temperature energy retention rate of the overall battery pack.
  • the positive electrode functional additive is a carbon-coated lithium-containing titanium niobium oxide.
  • titanium niobium oxide As a positive electrode functional additive, the conductivity of the titanium niobium oxide and the effective number of lithium ions in the battery cell can be improved, and the positive electrode functional additive can be improved.
  • the structural stability of titanium niobium oxide ensures the energy density and cycle stability of the battery cells.
  • the negative electrodes of the first battery cell, the second battery cell and the third battery cell have undergone lithium replenishment treatment.
  • the discharge cut-off voltage of the first battery cell is 1.4-1.6V
  • the discharge cut-off voltage of the second battery cell is 1.2-1.4V
  • the The discharge cut-off voltage of the third battery cell is 1.0-1.2V.
  • the first battery cell, the second battery cell, and the third battery cell can be The energy released at low temperatures is roughly the same, which can improve the overall energy retention rate of the battery pack at low temperatures.
  • the proportion of the first battery cells is approximately 10-30%
  • the number of the first battery cells is approximately 10-30%.
  • the number of second battery cells accounts for approximately 25-50%
  • the number of third battery cells accounts for approximately 30-60%.
  • the battery pack of the present application can be easily implemented.
  • a second aspect of the present application provides an electrical device, which includes the battery pack of the first aspect of the present application.
  • the electrical device has a strong endurance at low temperatures and can be used normally for a long time even at low temperatures.
  • Adopting the present invention by arranging battery cells with dual discharge voltage platforms and different low-temperature energy retention rates in regions with different temperatures inside the battery pack box, it is possible to provide a battery cell capable of releasing battery cells in regions with different temperatures at low temperatures.
  • a battery pack with approximately the same energy and an improved overall energy retention rate at low temperatures, and an electrical device including the battery pack.
  • 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.
  • FIG 3 is a schematic diagram of a 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 cathode active material of the battery cell is composed of the first cathode active material LiNi 0.6 Co It is composed of 0.2 Mn 0.2 O 2 (NCM) and positive electrode functional additive titanium niobium oxide (TNO, such as TiNb 2 O 7 ).
  • 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 the maximum range values 3, 4, and 5 are listed, the following ranges are all expected: 1-3, 1-4, 1-5, 2-3 , 2-4 and 2-5.
  • 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
  • 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.
  • steps (c) means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), also It may include steps (a), (c) and (b), or 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 thought that by arranging battery cells with better low-temperature discharge performance in areas with lower temperatures in the battery pack, the energy released by battery cells at different locations in the battery pack can be roughly consistent in low-temperature environments, thereby making The overall energy performance of the battery pack in low-temperature environments is improved, thereby improving the cruising range of electrical devices that use the battery pack as a power source in low-temperature environments.
  • the inventor repeatedly conducted research and found that by making the battery cells arranged in a lower temperature area have two discharge voltage platforms, after the discharge of the higher discharge voltage platform is completed, the lower one can continue to be used. Discharging at a discharge voltage platform can increase the discharge capacity of these battery cells, thereby making the discharge performance of these battery cells better at low temperatures.
  • the mass of the positive electrode functional additive in the battery cell accounts for the total mass of the positive electrode active material (the sum of the masses of the conventional positive electrode active material and the positive electrode functional additive) does not exceed a certain proportion (for example, 50%)
  • a certain proportion for example, 50%
  • the battery cells arranged in each area with different temperatures can exert their full potential at low temperatures. The energy is roughly the same, which can improve the energy retention rate of the entire battery pack at low temperatures, thereby improving the endurance of electrical devices such as electric vehicles that use the battery pack as a power source at low temperatures.
  • 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 1 shown in FIG. 1 with the case removed.
  • 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 first region R1 is a substantially rectangular region 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 case (for example, the length of the rectangular shape of the first region R1 The length and width may be approximately half of the length and width of the rectangular shape of the internal space of the battery pack box respectively), and the second region R2 is a substantially annular region between the first boundary line BL1 and the third boundary line BL3 , the third region R3 is a substantially annular region between the second boundary line BL2 and the 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 indicate the third boundary line BL1, the second boundary line BL2, and the third boundary line BL3. Virtual lines drawn for areas one, two and three.
  • 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 first battery cell 61 , the second battery cell 62 and the third battery cell 63 each have a first discharge voltage platform and a second discharge voltage platform, and the average discharge of the first discharge voltage platform The voltage is higher than the average discharge voltage of the second discharge voltage platform.
  • the respective positive electrode active materials of the first battery cell 61 , the second battery cell 62 and the third battery cell 63 are composed of the first positive electrode active material having the first discharge voltage platform and the positive electrode active material having the first discharge voltage platform.
  • the positive electrode functional additive of the second discharge voltage platform is mixed, and the positive electrode functional additive is titanium oxide, niobium oxide or titanium niobium oxide.
  • the corresponding discharge capacity ratio > the discharge capacity ratio corresponding to the second discharge voltage platform of the first battery cell 61 .
  • first battery cell is described as having a first discharge voltage platform and a second discharge voltage platform, or the positive electrode active material of the first battery cell is described as having The first cathode active material with the first discharge voltage platform and the cathode functional additive with the second discharge voltage platform are mixed, but only include the first discharge voltage platform and do not include the first battery cell of the second voltage discharge platform, That is, the first battery cell formed only of the first positive electrode active material is also within the scope of the present invention.
  • FIG. 3 is a schematic diagram of a 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 cathode active material of the battery cell is composed of the first cathode active material LiNi 0.6 Co It is composed of 0.2 Mn 0.2 O 2 (NCM) and positive electrode functional additive titanium niobium oxide (TNO, such as TiNb 2 O 7 ).
  • the lower limit of the discharge voltage platform of NCM is 2.5V (point A in Figure 3)
  • the upper limit of the discharge voltage platform of TNO is 1.8V (point B in Figure 3).
  • the discharge curve of a battery cell has two discharge voltage platforms, after passing point A, the discharge voltage drops sharply, and then levels off after falling to point B, and the discharge voltage platform continues to be used. Carry out discharge.
  • the point B where the first voltage drop ends is before the first discharge voltage platform (i.e., the high voltage discharge platform, also the first discharge voltage platform in this application), which is equal to the high voltage positive electrode in terms of data value.
  • the ratio of all the energy released by the active material to the current is a balanced value, which can also be roughly regarded as the average voltage before point B).
  • the second discharge voltage platform i.e. low
  • the voltage discharge platform, that is, the second discharge voltage platform in this application is embodied as the ratio of all the energy released by the low-voltage positive active material (such as the positive functional additive in this application) to the current (which is a balanced value, also It can be roughly regarded as the average voltage after point B).
  • low-temperature batteries with dual discharge voltage platforms are respectively configured in areas with different temperatures in the internal space of the battery pack box.
  • Battery cells 61, 62, and 63 with different energy retention rates are provided, and battery cells with higher low-temperature energy retention rates are arranged in regions with lower temperatures. Specifically, according to the normal temperature distribution inside the battery pack, the temperature of the first region R1 > the temperature of the second region R2 > the temperature of the third region R3 .
  • the second discharge of the third battery cell 63 The proportion of discharge capacity corresponding to the voltage platform > the proportion of discharge capacity corresponding to the second discharge voltage platform of the second battery cell 62 > the proportion of discharge capacity corresponding to the second discharge voltage platform of the first battery cell 61 .
  • Battery cells at different locations in the battery pack have different heat dissipation capabilities. Generally, the farther outside the battery cell is, the stronger its heat dissipation capacity is, that is, the faster the heat dissipation rate. As it moves from the outside of the battery pack to the inside of the battery pack, the heat dissipation rate of the battery cell gradually decreases; on the contrary, as it moves from the outside of the battery pack to the inside of the battery pack, the heat dissipation rate of the battery cell gradually decreases; on the contrary, as it moves from the outside of the battery pack to the inside of the battery pack, Moving toward the outside of the battery pack, the thermal insulation ability of the battery cells gradually decreases.
  • the temperatures of battery cells in different areas of the battery pack are different, resulting in inconsistent charge and discharge performance: for example, in a low-temperature external environment, the inner battery cells dissipate heat relatively slowly and have a relatively high temperature. The performance is relatively good (but the high-temperature performance is poor); however, the outer battery cells dissipate heat relatively quickly and the temperature is relatively low, and the performance in low-temperature external environments is relatively poor (but the high-temperature performance is high). Therefore, the excessive difference in electrical performance between battery cells in different areas of the battery pack in a low-temperature environment will reduce the energy retention rate of the entire battery pack in a low-temperature environment.
  • the inventor of the present application set up a first discharge voltage platform with a dual discharge voltage platform (ie, a first discharge voltage platform with a relatively high discharge voltage and a first discharge voltage platform with a relatively high discharge voltage) in the first region R1, the second region R2 and the third region R3 with different temperatures.
  • the first battery cell 61, the second battery cell 62 and the third battery cell 63 can be reused after the discharge of the first discharge voltage platform is completed.
  • the discharge voltage platform continues to discharge (i.e., realizes ladder discharge of the same battery cell), thereby increasing the energy released by each battery cell in a low-temperature environment, thereby improving the low-temperature energy retention rate of the overall battery pack.
  • the positive active materials of the first battery cell 61, the second battery cell 62 and the third battery cell 63 with dual discharge voltage platforms are composed of conventional positive electrode active materials (first positive electrode active materials) and positive electrode functional assistants. Prepared by mixing agents.
  • Conventional cathode active materials have a first discharge voltage platform with a high discharge voltage.
  • the cathode functional additives are titanium oxide, niobium oxide or titanium niobium oxide with a layered structure of ReO 3 configuration. These cathode functional additives have The second discharge voltage platform with lower discharge voltage.
  • the discharge capacity of the second discharge voltage platform with a lower discharge voltage in the battery cell can be adjusted by changing the content of the positive electrode functional additive in the positive electrode active material.
  • the inventor of the present application found that by further adjusting the proportion of discharge capacity corresponding to the second discharge voltage platform of the first battery cell 61, the second battery cell 62 and the third battery cell 63, the overall low-temperature energy retention rate can be obtained Higher battery pack 1, and this setup significantly improves the low-temperature energy retention rate of the battery pack under low-temperature conditions in winter.
  • the proportion of discharge capacity corresponding to the second discharge voltage platform can enable the second battery cell 62 and the third battery cell 63 to continue to discharge in a low temperature environment where the first battery cell 61 cannot continue to discharge.
  • the third cell 63 is allowed to continue discharging to ensure that the overall discharge capacity of the battery pack is at a relatively high level.
  • the inventor further compared the proportion of discharge capacity corresponding to the second discharge voltage platform in each battery cell 61, 61, 63 with dual discharge voltage platforms arranged in the regions R1, R2, and R3 with different temperatures and the battery pack.
  • the relationship between total energy retention at -20°C was studied in depth.
  • 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 positive electrode functional additive in the first battery cell 61 , the second battery cell 62 and the third battery cell 63 is titanium niobium oxide represented by Ti 2 Nb 2x O 4+5x , where x is an integer above 1, optionally, the titanium niobium oxide is one selected from Ti 2 Nb 2 O 9 , TiNb 2 O 7 , Ti 2 Nb 10 O 29 and TiNb 24 O 62 or Various.
  • Titanium niobium oxide is generally produced by combining titanium oxide and niobium oxide in different proportions. Since the atomic radii of titanium and niobium are similar, titanium niobium oxide has a layered structure of ReO 3 configuration, and titanium ions and niobium The ions also have similar electrochemical properties. The redox potentials of Nb 5+ /Nb 4+ , Nb 4+ /Nb 3+ and Ti 4+ /Ti 3+ have small differences, all in the range of 1-2V.
  • the battery pack of the present application with excellent low-temperature performance can be realized.
  • the above-mentioned titanium niobium oxide can be purchased commercially, or prepared by the following method: according to the Ti 2 Nb 2x O 4 + 5x element ratio, adjust the mass ratio of TiO 2 and Nb 2 O 5 powder, add a solvent, the solvent can It is ethanol, water or acetone. The mixture can be ball milled, dried, heated and cooled to obtain the corresponding titanium niobium oxide.
  • the discharge voltage range of the second discharge voltage platform is 1.0-2.0V.
  • the discharge capacity of the second discharge voltage platform at 1.2-1.6V accounts for the second discharge voltage platform. More than 50% of the total discharge capacity, optionally more than 70%.
  • the discharge voltage of the second discharge voltage platform can be significantly different from the discharge voltage of the first discharge voltage platform, and a dual discharge voltage platform can be significantly obtained. the above-mentioned effects.
  • the ratio of the discharge capacity of the second discharge voltage platform at 1.2-1.6V to the total discharge capacity of the second discharge voltage platform within the above range, it can be ensured that the battery cells can release sufficient energy at low temperatures, thereby ensuring that the battery Including the overall low temperature energy retention rate.
  • the lowest discharge voltage of the first discharge voltage platform and the highest discharge voltage of the second discharge voltage platform are The difference is above 0.5V, optionally above 1.0V.
  • the "lowest discharge voltage of the first discharge voltage platform” described in this application refers to the discharge voltage corresponding to point A
  • the “highest discharge voltage of the second discharge voltage platform” refers to the discharge corresponding to point B. Voltage.
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 90%-100%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 0%-10%.
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 100%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 0%, which refers to the situation where the first battery cell 61 has only one discharge voltage platform, in which are also within the scope of the present invention.
  • the performance of the first battery cell 61 can be improved.
  • the energy that can be released at low temperatures thereby improves the overall low-temperature energy retention rate of the battery pack 1.
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 73%-95%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 5%-27%.
  • the proportions of the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform in the second battery cell 62 can be within the above range, the performance of the second battery cell 62 can be improved.
  • the energy that can be released at low temperatures further improves the overall low-temperature energy retention rate of the battery pack 1.
  • the third battery cell 63 when the sum of the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform is 100%, the The discharge capacity corresponding to the first discharge voltage platform accounts for 54%-87%, and the discharge capacity corresponding to the second discharge voltage platform accounts for 13%-46%.
  • the performance of the third battery cell 63 can be improved.
  • the energy that can be released at low temperatures further improves the overall low-temperature energy retention rate of the battery pack 1.
  • the gram capacity of the positive active material of the first battery cell 61 is 148-285 mAh/g, and the gram capacity of the positive active material of the second battery cell is 155-295 mAh/g, so The gram capacity of the positive electrode active material of the third battery cell is 169-311 mAh/g.
  • the first battery cell 61 , the second battery cell 62 , and the third battery cell 63 are set within the above range, it is possible to make the first battery cell 61 , the second battery cell 62 , and the third battery cell 63 .
  • the discharge capacities of the third battery cells 63 at low temperatures are substantially the same, which improves the energy retention rate of the entire battery pack 1 at low temperatures.
  • the gram capacity of the positive active material of each battery cell refers to the average gram capacity of the positive active material. For example, it can be based on the respective gram capacity and mass proportion of the first positive active material and the positive functional additive contained in the positive active material. Calculate the ratio.
  • the theoretical gram capacity of the positive electrode functional additive is 350-410 mAh/g.
  • the first positive electrode active material is one selected from the group consisting of lithium manganate, lithium nickelate, lithium cobalt oxide, lithium nickel cobalt manganate, lithium nickel cobalt aluminate, and lithium iron phosphate.
  • the first cathode active material can be used from now on.
  • the battery pack of the present application can be easily realized using existing cathode active materials.
  • the mass proportion of the first positive active material to the positive active material decreases in the order of the first battery cell 61, the second battery cell 62, and the third battery cell 63,
  • the mass proportion of the positive electrode functional additive to the positive electrode active material increases in the order of the first battery cell 61 , the second battery cell 62 , and the third battery cell 63 .
  • the mass of the first cathode active material accounts for 96.0%-100%, and the mass of the positive electrode functional additive accounts for 0%-4.0%.
  • the mass of the first cathode active material accounts for 100%, and the mass of the cathode functional additive accounts for 0%, refers to the situation where the first battery cell 61 is formed only of the first cathode active material, which is also the case here. within the scope of the invention.
  • the discharge corresponding to the first discharge voltage plateau in the first battery cell 61 can be achieved.
  • the respective proportions of the capacity and the discharge capacity corresponding to the second discharge voltage platform are within the above range, which can increase the energy that the first battery cell 61 can release at low temperatures, thereby improving the overall low-temperature energy retention rate of the battery pack 1 .
  • the mass of the first cathode active material accounts for 88.5%-96.0%
  • the mass of the positive electrode functional additive accounts for 4.0%-11.5%.
  • the mass ratio of the first positive electrode active material and the positive electrode functional additive in the second battery cell 62 within the above range, the discharge corresponding to the first discharge voltage plateau in the second battery cell 62 can be achieved.
  • the respective proportions of the capacity and the discharge capacity corresponding to the second discharge voltage platform are within the above range, which can increase the energy that the second battery cell 62 can release at low temperatures, thereby further improving the overall low-temperature energy retention rate of the battery pack 1 .
  • the mass of the first cathode active material accounts for 76.5%-88.5%
  • the mass of the positive electrode functional additive accounts for 11.5%-23.5%.
  • the mass ratio of the first positive electrode active material and the positive electrode functional additive in the third battery cell 63 within the above range, the discharge corresponding to the first discharge voltage plateau in the third battery cell 63 can be achieved.
  • the respective proportions of the capacity and the discharge capacity corresponding to the second discharge voltage platform are within the above range, which can increase the energy that the third battery cell 63 can release at low temperatures, thereby further improving the overall low-temperature energy retention rate of the battery pack 1 .
  • the positive electrode functional additive is a carbon-coated lithium-containing titanium niobium oxide.
  • the reduction in the number of lithium ions caused by the reduction of conventional positive electrode active materials can be compensated, so that the battery cells have the characteristics
  • the required number of lithium ions ensures the energy density of the battery cell.
  • carbon coating the titanium niobium oxide that has undergone prelithiation treatment the conductivity of the titanium niobium oxide can be improved. Therefore, the structural stability of titanium niobium oxide as a positive electrode functional additive can be improved to ensure the energy density and cycle stability of the battery cell.
  • a well-known method for prelithiating lithium-deficient substances can be used.
  • the following method can be used: after mixing the prepared titanium niobium oxide and lithium carbonate, Compact and place it in an alumina ceramic crucible, place it in a blast furnace and heat it to the melting temperature of lithium carbonate, cool it to room temperature and take it out for ball milling and dispersion to obtain a pre-lithiated product.
  • the first efficiency of the battery can be improved.
  • a known carbon coating method can be used as a method of carbon coating the prelithiated titanium niobium oxide.
  • a known carbon coating method can be used.
  • the following method can be used: According to titanium niobium oxide (Ti 2 Nb 2x O 4+5x ) The proportion of each element and the required amount of carbon coating are adjusted. The mass ratio of pre-lithiated titanium niobium oxide and glucose is added.
  • the solvent can be ethanol, water or acetone. The mixture is ball milled, dried and granulated. After calcination, the carbon-coated titanium-niobium oxide material containing lithium element can be obtained.
  • the electrical conductivity of the titanium niobium oxide can be improved.
  • the negative electrodes of the first battery cell 61 , the second battery cell 62 and the third battery cell 63 have undergone lithium replenishment treatment.
  • the loss of lithium ions caused by the addition of titanium niobium oxide to the positive electrode active material can be compensated. Insufficient, so that the total amount of effective lithium ions in the battery cell is not reduced, thereby ensuring the energy density of the battery cell.
  • a method for replenishing lithium on the negative electrode various known methods can be used. For example, the following method can be used: (1) Mix the binder, lithium powder and organic solvent to obtain a lithium powder solution; (2) Use The lithium powder solution is physically coated on the negative electrode piece; (3) the negative electrode piece is dried and cold-pressed to obtain a pre-lithiated negative electrode piece. By replenishing lithium in the negative electrode, the first efficiency of the battery can be improved.
  • At least one of the prelithiation treatment of the positive electrode functional additive and the lithium supplementation treatment of the negative electrode may be performed.
  • the discharge cut-off voltage of the first battery cell is 1.4-1.6V
  • the discharge cut-off voltage of the second battery cell is 1.2-1.4V
  • the The discharge cut-off voltage of the third battery cell is 1.0-1.2V.
  • the first battery cell 61 , the second battery cell 62 and the third battery cell 63 can be discharged.
  • the energy released by the three battery cells 63 at low temperatures is approximately the same, thereby improving the energy retention rate of the entire battery pack at low temperatures.
  • Charging cut-off voltage that is too high or discharge cut-off voltage that is too low will damage the cycle performance of the battery cells.
  • the charge cut-off voltage is too high, the battery cell will be overcharged.
  • the oxygen released by the decomposition of the cathode material will react with the electrolyte.
  • the liquid will undergo a violent chemical reaction, and the worst result may be an explosion.
  • the discharge cut-off voltage is too low, the battery cell will over-discharge. Over-discharge will increase the internal pressure of the battery cell and destroy the reversibility of the positive and negative active materials. Even if it is charged, it can only be partially restored and the capacity will be reduced. Significant attenuation. Deep charging and deep discharge of a battery cell will increase the loss of the battery cell.
  • the ideal working state of the battery cell is shallow charging and shallow discharge, which can extend the life of the battery cell.
  • the proportion of the first battery cells 61 is approximately 10- 30%
  • the second battery cell 62 accounts for approximately 25-50%
  • the third battery cell 63 accounts for approximately 30-60%.
  • the number of first battery cells 61 may be one.
  • the battery pack of the present application can be easily implemented.
  • the present application also provides an electrical device, which includes the battery pack of the present 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 LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) as the cathode active material and the cathode functional assistant TiNb 2 O 7 , superconducting carbon black SP as the conductive agent and polyvinylidene fluoride as the binder Ethylene (PVDF) is dispersed in N-methylpyrrolidone (NMP) as a solvent and mixed evenly to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on the positive electrode current collector aluminum foil, dried, cold pressed, slit, After cutting, the positive electrode piece is obtained.
  • NMP N-methylpyrrolidone
  • the positive electrode functional additive has been pre-lithiated and carbon coated in advance.
  • the mass ratio of the positive electrode active material, conductive carbon black, and binder PVDF is 96:2:2.
  • the mass ratio of the positive active material NCM is 2:98.
  • the negative active material graphite Disperse the negative active material graphite, superconducting carbon black SP as the conductive agent, SBR as the binder, and CMC-Na as the thickener in deionized water as the solvent at a mass ratio of 96:1:1:2 and mix. 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.
  • ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent, and then dissolve the fully dried lithium salt LiPF 6 in the mixture.
  • 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.
  • the first battery cell I-2 was obtained in the same manner as in Preparation Example I-1, except that the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive TiO 2 were used as the positive electrode active material.
  • NCM first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2
  • TiO 2 positive electrode functional additive
  • the first battery cell I- was obtained in the same manner as Preparation Example I-1 except that the positive electrode active material used the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive Nb 2 O 5 3.
  • the positive electrode active material used the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive Nb 2 O 5 3.
  • the first battery cell I-4 was obtained in the same manner as Preparation Example I-1, except that the first positive electrode active material lithium iron phosphate (LFP) and the positive electrode functional additive TiNb 2 O 7 were used as the positive electrode active material.
  • LFP lithium iron phosphate
  • TiNb 2 O 7 the positive electrode functional additive
  • the first battery cell I-5 was obtained in the same manner as in Preparation Example I-1, except that the first positive electrode active material lithium manganate (LMO) and the positive electrode functional additive TiNb 2 O 7 were used as the positive electrode active material.
  • LMO lithium manganate
  • TiNb 2 O 7 the positive electrode functional additive
  • the first battery cell was obtained in the same manner as Preparation Example I-1 except that the positive electrode active material used the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive Ti 2 Nb 2 O 9 I-6.
  • the positive electrode active material used the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive Ti 2 Nb 2 O 9 I-6.
  • the first battery cell was obtained in the same manner as Preparation Example I-1 except that the positive electrode active material used the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive Ti 2 Nb 10 O 29 I-7.
  • the positive electrode active material used the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive Ti 2 Nb 10 O 29 I-7.
  • the first battery cell I- was obtained in the same manner as Preparation Example I-1, except that the first positive electrode active material LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) and the positive electrode functional additive TiNb 24 O 62 were used as the positive electrode active material. 8.
  • the first battery cell I-9 was obtained in the same manner as Preparation Example I-1, except that the first positive electrode active material lithium iron phosphate (LFP) and the positive electrode functional additive Ti 2 Nb 2 O 9 were used as the positive electrode active material.
  • LFP lithium iron phosphate
  • Ti 2 Nb 2 O 9 the positive electrode functional additive
  • the first battery cell I-10 was obtained in the same manner as Preparation Example I-1, except that the first positive electrode active material lithium manganate (LMO) and the positive electrode functional additive Ti 2 Nb 10 O 29 were used as the positive electrode active material.
  • LMO lithium manganate
  • Ti 2 Nb 10 O 29 the positive electrode active material
  • the first battery cell I-11 was obtained in the same manner as in Preparation Example I-1 except that only NCM was used as the positive electrode active material.
  • the first battery cell I-12 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material NCM was 11.5:88.5.
  • the first battery cell I-13 was obtained in the same manner as in Preparation Example I-1 except that only LFP was used as the positive electrode active material.
  • the first battery cell I-14 was obtained in the same manner as Preparation Example I-4 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LFP was 4:96.
  • the second battery cell II-1 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material NCM was 6.5:93.5.
  • the second battery cell II-2 was obtained in the same manner as Preparation Example I-2 except that the mass ratio of the positive electrode functional additive TiO 2 to the first positive electrode active material NCM was 6.5:93.5.
  • the second battery cell II-3 was obtained in the same manner as Preparation Example I-3 except that the mass ratio of the positive electrode functional additive Nb 2 O 5 to the first positive electrode active material NCM was 6.5:93.5.
  • the second battery cell II-4 was obtained in the same manner as Preparation Example I-4 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LFP was 6.5:93.5.
  • the second battery cell II-5 was obtained in the same manner as Preparation Example I-5, except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LMO was 6.5:93.5.
  • the second battery cell II-6 was obtained in the same manner as Preparation Example I-6, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 2 O 9 to the first positive electrode active material NCM was 6.5:93.5.
  • the second battery cell II-7 was obtained in the same manner as Preparation Example I-7, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 10 O 29 to the first positive electrode active material NCM was 6.5:93.5.
  • the second battery cell II-8 was obtained in the same manner as in Preparation Example I-8, except that the mass ratio of the positive electrode functional additive TiNb 24 O 62 to the first positive electrode active material NCM was 6.5:93.5.
  • the second battery cell II-9 was obtained in the same manner as Preparation Example I-9, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 2 O 9 to the first positive electrode active material LFP was 6.5:93.5.
  • the second battery cell II-10 was obtained in the same manner as in Preparation Example I-10, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 10 O 29 to the first positive electrode active material LMO was 6.5:93.5.
  • the second battery cell II-11 was obtained in the same manner as in Preparation Example I-11.
  • the second battery cell II-12 was obtained in the same manner as in Preparation Example I-1 except that only LFP was used as the positive electrode active material.
  • the second battery cell II-13 was obtained in the same manner as in Preparation Example I-1.
  • the second battery cell II-14 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material NCM was 4:96.
  • the second battery cell II-15 was obtained in the same manner as Preparation Example I-4 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LFP was 11.5:88.5.
  • the mass ratio of the positive functional additive Ti 2 Nb 2 O 9 to the first positive active material LMO is Except for the ratio of 11.5:88.5, the second battery cell II-16 was obtained in the same manner as in Preparation Example I-1.
  • the second battery cell II-17 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material NCM was 20:80.
  • the third battery cell III-1 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material NCM was 11.5:88.5.
  • the third battery cell III-2 was obtained in the same manner as in Preparation Example I-2, except that the mass ratio of the positive electrode functional additive TiO 2 to the first positive electrode active material NCM was 11.5:88.5.
  • the third battery cell III-3 was obtained in the same manner as Preparation Example I-3, except that the mass ratio of the positive electrode functional additive Nb 2 O 5 to the first positive electrode active material NCM was 11.5:88.5.
  • the third battery cell III-4 was obtained in the same manner as Preparation Example I-4 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LFP was 11.5:88.5.
  • the third battery cell III-5 was obtained in the same manner as in Preparation Example I-5, except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LMO was 11.5:88.5.
  • the third battery cell III-6 was obtained in the same manner as Preparation Example I-6, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 2 O 9 to the first positive electrode active material NCM was 11.5:88.5.
  • the third battery cell III-7 was obtained in the same manner as Preparation Example I-7, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 10 O 29 to the first positive electrode active material NCM was 11.5:88.5.
  • the third battery cell III-8 was obtained in the same manner as in Preparation Example I-8, except that the mass ratio of the positive electrode functional additive TiNb 24 O 62 to the first positive electrode active material NCM was 11.5:88.5.
  • the third battery cell III-9 was obtained in the same manner as Preparation Example I-9 except that the mass ratio of the positive electrode functional additive Ti 2 Nb 2 O 9 to the first positive electrode active material LFP was 11.5:88.5.
  • the third battery cell III-10 was obtained in the same manner as Preparation Example I-10, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 10 O 29 to the first positive electrode active material LMO was 11.5:88.5.
  • the third battery cell III-11 was obtained in the same manner as in Preparation Example I-11.
  • the third battery cell III-12 was obtained in the same manner as in Preparation Example I-1 except that only LMO was used as the positive electrode active material.
  • the third battery cell III-13 was obtained in the same manner as in Preparation Example I-1.
  • the third battery cell III-14 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material NCM was 23.5:76.5.
  • the third battery cell III-15 was obtained in the same manner as Preparation Example I-4 except that the mass ratio of the positive electrode functional additive TiNb 2 O 7 to the first positive electrode active material LFP was 23.5:76.5.
  • the third battery cell III-16 was obtained in the same manner as Preparation Example II-16, except that the mass ratio of the positive electrode functional additive Ti 2 Nb 2 O 9 to the first positive electrode active material LMO was 23.5:76.5.
  • the internal space of the battery pack box is divided into a first region R1, a second region R2 and a third region R3.
  • the first battery cell I-1 is configured as the first battery cell in the first region R1.
  • body 61 arrange the second battery cell II-1 as the second battery cell 62 in the second region R2, and configure the third battery cell III-1 as the third battery cell 63 in the third region R3, and assemble into battery pack.
  • the number of first battery cells 61:the number of second battery cells 62:the number of third battery cells 63 12:32:40.
  • Example 1 In addition to using the first battery cell I-2 to replace the first battery cell I-1, using the second battery cell II-2 to replace the second battery cell II-1, and using the third battery cell III-2 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-3 to replace the first battery cell I-1, using the second battery cell II-3 to replace the second battery cell II-1, and using the third battery cell III-3 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-4 to replace the first battery cell I-1, using the second battery cell II-4 to replace the second battery cell II-1, and using the third battery cell III-4 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-5 to replace the first battery cell I-1, using the second battery cell II-5 to replace the second battery cell II-1, and using the third battery cell III-5 to replace the third battery cell I-5. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-6 to replace the first battery cell I-1, using the second battery cell II-6 to replace the second battery cell II-1, and using the third battery cell III-6 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-7 to replace the first battery cell I-1, using the second battery cell II-7 to replace the second battery cell II-1, and using the third battery cell III-7 to replace the third battery cell I-7. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-8 to replace the first battery cell I-1, using the second battery cell II-8 to replace the second battery cell II-1, and using the third battery cell III-8 to replace the third battery cell I-8. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-9 to replace the first battery cell I-1, using the second battery cell II-9 to replace the second battery cell II-1, and using the third battery cell III-9 to replace the third battery cell I-9. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-10 to replace the first battery cell I-1, using the second battery cell II-10 to replace the second battery cell II-1, and using the third battery cell III-10 to replace the third battery cell I-10. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-11 to replace the first battery cell I-1, using the second battery cell II-14 to replace the second battery cell II-1, and using the third battery cell III-14 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-13 to replace the first battery cell I-1, using the second battery cell II-15 to replace the second battery cell II-1, and using the third battery cell III-15 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-14 to replace the first battery cell I-1, using the second battery cell II-16 to replace the second battery cell II-1, and using the third battery cell III-16 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-12 to replace the first battery cell I-1, using the second battery cell II-17 to replace the second battery cell II-1, and using the third battery cell III-14 to replace the first battery cell I-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • the battery pack was assembled in the same manner as in Example 1.
  • the battery pack was assembled in the same manner as in Example 1.
  • the battery pack was assembled in the same manner as in Example 1.
  • the battery pack was assembled in the same manner as in Example 1.
  • Example 1 In addition to using the first battery cell I-11 to replace the first battery cell I-1, using the second battery cell II-11 to replace the second battery cell II-1, and using the third battery cell III-11 to replace the third battery cell I-11. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • Example 1 In addition to using the first battery cell I-11 to replace the first battery cell I-1, using the second battery cell II-12 to replace the second battery cell II-1, and using the third battery cell III-12 to replace the third battery cell I-11. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • the internal space of the battery pack box is divided into a first area, a second area and a third area
  • the battery pack of the present application is not limited to the battery pack box.
  • the internal space is divided into three areas, in addition to the first area, the second area and the third area, there may be one or more areas outside the third area, as long as the areas arranged in the outer area
  • the battery cells may be arranged around the battery cells arranged in an area inside the battery cells.
  • the proportion of the discharge capacity corresponding to the second discharge voltage platform of the battery cell is higher (i.e. , the higher the mass proportion of the cathode functional additive in the cathode active material of the battery cell).
  • the four corners of the rectangular shape may be used as the outermost area. In this area, the discharge corresponding to the second discharge voltage plateau of the battery cell is The capacity accounts for the highest proportion (that is, the cathode functional additives in the positive electrode active material of the battery cell account for the highest mass proportion).
  • a Xinwei power battery testing machine (model BTS-5V300A- 4CH) measure the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform of the first battery cell, the second battery cell and the third battery cell at 25°C, and then calculate the first The proportion of discharge capacity corresponding to the second discharge voltage platform of each of the 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 (4) obtain the discharge curve in step (4), for example, such as the discharge curve in Figure 3 of this application.
  • the total discharge capacity before point B is corresponding to the first discharge voltage platform.
  • Discharge capacity C1 the discharge capacity from point B to the discharge cut-off voltage is the discharge capacity C2 corresponding to the second discharge voltage platform.
  • Types of positive electrode active materials Charge cut-off voltage (V) Discharge cut-off voltage (V) NCM+TiNb 2 O 7 4.40 1.45 NCM+TiO 2 4.40 1.45 NCM+Nb 2 O 5 4.40 1.45 LFP+TiNb 2 O 7 3.80 1.45 LMO+TiNb 2 O 7 4.40 1.45 NCM+Ti 2 Nb 2 O 9 4.40 1.45 NCM+Ti 2 Nb 10 O 29 4.40 1.45 NCM+TiNb 24 O 62 4.40 1.45 LFP+Ti 2 Nb 2 O 9 3.80 1.45 LMO+Ti 2 Nb 10 O 29 4.40 1.45 LMO+Ti 2 Nb 2 O 9 4.40 1.45 LMO+Ti 2 Nb 2 O 9 4.40 1.45 LMO+Ti 2 Nb 2 O 9 4.40 1.45
  • 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 battery pack at -20°C.
  • the total full discharge energy of the battery pack is divided by the total full discharge energy of the battery pack at -20°C 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 -20°C.
  • the first battery cell, the second battery cell and the third battery cell all have a first discharge voltage platform and a second discharge voltage platform, and the The proportion of discharge capacity corresponding to the second discharge voltage platform of the three battery cells > the proportion of discharge capacity corresponding to the second discharge voltage platform of the second battery cell > the discharge capacity corresponding to the second discharge voltage platform of the first battery cell
  • the total energy retention rate of the battery pack at -20°C reaches 65.0%-76.7%.
  • the first battery cell, the second battery cell and the third battery cell all have only one discharge voltage platform, and the total energy retention rate of the battery pack at -20°C is only 60.5% and 56.7%.
  • both the second battery cell and the third battery cell have a first discharge voltage platform and a second discharge voltage platform
  • the third battery cell has a first discharge voltage platform and a second discharge voltage platform.
  • the mass proportion of the cathode functional additive in each of the first battery cell, the second battery cell and the third battery cell and the proportion of discharge capacity corresponding to the second discharge voltage platform are within the preferred ranges recorded in this application, and the battery
  • the total energy retention rate at -20°C reaches 64.1%-70.0%.
  • Example 15 the mass proportion of the cathode functional additive in each of the first battery cell and the second battery cell and/or the proportion of discharge capacity corresponding to the second discharge voltage platform is preferably as described in this application. Outside the range, the total energy retention rate of the battery pack at -20°C is 59.3%.
  • the first battery cell, the second battery cell and the third battery cell all have a first discharge voltage platform and a second discharge voltage platform, and the third battery cell
  • the proportion of discharge capacity corresponding to the second discharge voltage platform of the first battery cell, and , the discharge cut-off voltages of the first battery cell, the second battery cell and the third battery cell at -20°C are all within the preferred ranges recorded in this application, and the total energy retention rate of the battery pack at -20°C reaches 70%.
  • Example 16 the discharge cut-off voltage of the second battery cell and the third battery cell is too high at -20°C, and the total energy retention rate of the battery pack at -20°C is 55%, which shows that the cut-off voltage is lower than -20°C. °C has a great influence on the total energy retention rate.
  • Example 17 the discharge cut-off voltage of the first battery cell and the second battery cell is too low.
  • the total energy retention rate of the battery pack at -20°C is 71%, when the cut-off voltage is too low, it can be improved -
  • the total energy retention rate at 20°C is equivalent to over-discharge, but it will cause the performance of the battery cells to deteriorate and generate gas, affecting the life of the battery cells.
  • Example 18 the discharge cut-off voltage of the second battery cell at -20°C is too high and is greater than the discharge cut-off voltage of the first battery cell, and the total energy retention rate of the battery pack at -20°C is 62%.
  • Example 19 at -20°C, the discharge cut-off voltage of the first battery cell is too low, the discharge cut-off voltage of the third battery cell is too high, and the discharge cut-off voltage of the third battery cell is > the second battery cell.

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Abstract

一种电池包（1）以及包括电池包（1）的用电装置。电池包（1）包括电池包箱体和被收纳在电池包箱体中不同区域的第一、第二、第三电池单体（61、62、63），第一、第二、第三电池单体（61、62、63）各自均具有第一、第二放电电压平台，第一放电电压平台的平均放电电压高于第二放电电压平台的平均放电电压，第一、第二、第三电池单体（61、62、63）具有不同的第二放电电压平台对应的放电容量占比。通过在电池包箱体内部的温度不同的区域配置具有第一、第二放电电压平台的低温能量保持率不同的电池单体，能够使电池包的温度不同的区域的电池单体在低温下释放的能量大致一致、电池包整体的低温能量保持率提高。

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。
为了达到上述目的，本申请的第一方面提供一种电池包，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，所述电池包箱体的内部空间包括第一区域、第二区域和第三区域，在所述第一区域中配置有第一电池单体，在所述第二区域中配置有第二电池单体，在所述第三区域中配置有第三电池单体，所述第二电池单体包围所述第一电池单体的周围排布，所述第三电池单体包围所述第二电池单体的周围排布，所述第一电池单体、所述第二电池单体和所述第三电池单 体各自具有第一放电电压平台和第二放电电压平台，所述第一放电电压平台的平均放电电压高于所述第二放电电压平台的平均放电电压，所述第一电池单体、所述第二电池单体和所述第三电池单体各自的正极活性物质由具有所述第一放电电压平台的第一正极活性物质和具有所述第二放电电压平台的正极功能助剂混合而成，所述正极功能助剂为钛氧化物、铌氧化物或钛铌氧化物，在所述第一电池单体、所述第二电池单体和所述第三电池单体各自中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第三电池单体的所述第二放电电压平台对应的放电容量占比＞所述第二电池单体的所述第二放电电压平台对应的放电容量占比＞所述第一电池单体的所述第二放电电压平台对应的放电容量占比。
由此，本申请通过按照电池包内的温度分布来设置低温下的放电能力不同的电池单体从而改善电池包整体在低温下的能量保持率。具体而言，在电池包箱体的内部空间的温度不同的区域中分别配置具有双放电电压平台(放电电压较高的第一放电电压平台和放电电压较低的第二放电电压平台)的低温能量保持率不同的电池单体，并且在温度越低的区域配置低温能量保持率越高的电池单体。通过在电池包箱体的内部空间中的温度相对较高的区域配置低温性能相对较低(低温能量保持率相对较小)的电池单体，在电池包箱体的内部空间中的温度相对较低的区域配置低温性能相对较高(低温能量保持率相对较大)的电池单体，能够使电池包的温度不同的各区域中的电池单体的循环一致性更高，提升电池包整体的低温能量保持率，从而提高电池包整体的低温续航能力。
本申请中具有双放电电压平台的电池单体的正极活性物质由常规正极活性物质(第一正极活性物质)和正极功能助剂混合制备而成，常规正极活性物质具有放电电压较高的第一放电电压平台，正极功能助剂为钛氧化物、铌氧化物或者钛铌氧化物，这些正极功能助剂具有放电电压较低的第二放电电压平台。电池单体中的放电电压较低的第二放电电压平台的放电容量，可通过改变正极活性物质中的正极功能助剂的含量来进行调节。通过使用具有双放电电压平台的电池单体，能够在利用放电电压较高的第一放电电压平台进行放电之后，继续利 用放电电压较低的第二放电电压平台进行放电，显著提升电池单体的放电功率，尤其是在低温条件下的放电功率，从而使电池单体具有更高的低温能量保持率。
本申请所述电池包的形状是任意的，可以是根据客户要求设计的任意形状。
本申请所述电池包中，电池包箱体的内部空间并不限于划分为上述的3个区域，只要包括上述的第一区域、第二区域和第三区域即可。具体而言，可以是电池包箱体的内部空间由上述的第一区域、第二区域和第三区域组成；也可以是电池包箱体的内部空间中除了上述的第一区域、第二区域和第三区域以外，在第三区域的外侧还具有一个或多个区域，只要配置在外侧的区域中的电池单体包围配置在其内侧的区域中的电池单体的周围排布即可。
本申请所述电池包，在电池包箱体的内部空间包括如上所述的3个以上的区域的情况下，只要满足越靠外侧的区域中，电池单体的第二放电电压平台对应的放电容量占比越高(即，电池单体的正极活性物质中的正极功能助剂的质量占比越高)即可。
在一些实施方式中，在电池包箱体的内部空间为矩形形状的情况下，可以是将该矩形形状的四个角作为最外侧的区域，在该区域中，电池单体的第二放电电压平台对应的放电容量占比最高(即，电池单体的正极活性物质中的正极功能助剂的质量占比最高)。
在一些实施方式中，所述电池包箱体的所述内部空间由所述第一区域、所述第二区域和所述第三区域组成。
由此，能够在电池包箱体的内部空间被划分为上述的第一区域、第二区域和第三区域这3个区域的电池包中，获得上述的优异效果。
在一些实施方式中，所述正极功能助剂为由Ti 2Nb 2xO 4+5x表示的钛铌氧化物，其中x为1以上的整数，可选地，所述钛铌氧化物为选自Ti 2Nb 2O 9、TiNb 2O 7、Ti 2Nb 10O 29和TiNb 24O 62中的一种或多种。
由此，通过选择性能优异的钛铌氧化物作为正极功能助剂，能够得到具有合适的第二放电电压平台的电池单体，从而能够实现低温性能优异的本申请电池包。
在一些实施方式中，所述第二放电电压平台的放电电压范围为 1.0-2.0V，可选地，所述第二放电电压平台在1.2-1.6V的放电容量占所述第二放电电压平台的总放电容量的50％以上，可选为70％以上。
由此，通过使第二放电电压平台的放电电压在上述范围内，能够使第二放电电压平台的放电电压与第一放电电压平台的放电电压具有明显差异，能够显著地获得具有双放电电压平台所带来的上述效果。通过使第二放电电压平台在1.2-1.6V的放电容量占第二放电电压平台的总放电容量的比例在上述范围内，能够确保电池单体在低温下能够释放出足够的能量，从而确保电池包整体的低温能量保持率。
在一些实施方式中，在所述第一、第二、第三电池单体中，所述第一放电电压平台的最低放电电压与所述第二放电电压平台的最高放电电压之差为0.5V以上，可选为1.0V以上。
由此，能够利用放电电压较高的第一放电电压平台进行放电之后，继续利用放电电压较低的第二放电电压平台进行放电，能够显著提高各电池单体在低温下能够释放的能量，从而提升电池包整体在低温下的能量保持率。
在一些实施方式中，在所述第一电池单体中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占90％-100％，所述第二放电电压平台对应的放电容量占0％-10％。
由此，通过使第一电池单体中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第一电池单体在低温下能够释放的能量，从而提升电池包整体的低温能量保持率。
在一些实施方式中，在所述第二电池单体中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占73％-95％，所述第二放电电压平台对应的放电容量占5％-27％。
由此，通过使第二电池单体中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第二电池单体在低温下能够释放的能量，从而进一步提升电池包整体的低温能量保持率。
在一些实施方式中，在所述第三电池单体中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占54％-87％，所述第二放电电压平台对应的放电容量占13％-46％。
由此，通过使第三电池单体中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第三电池单体在低温下能够释放的能量，从而更进一步提升电池包整体的低温能量保持率。
在一些实施方式中，所述第一电池单体的正极活性物质的克容量为148-285mAh/g，所述第二电池单体的正极活性物质的克容量为155-295mAh/g，所述第三电池单体的正极活性物质的克容量为169-311mAh/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，提高电池包整体在低温下的能量保持率。
在一些实施方式中，所述正极功能助剂的理论克容量为350-410mAh/g。
由此，通过使用理论克容量在上述范围内的正极功能助剂，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，所述第一正极活性物质为选自锰酸锂、镍酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂和磷酸铁锂中的一种。
由此，只要由第一正极活性物质产生的第一放电电压平台与由正极功能助剂产生的第二放电电压平台的放电电压和放电容量占比满足上述关系，第一正极活性物质可以从现有的各种正极活性物质中选择，从而，能够利用现有的正极活性物质容易地实现本申请的电池包。
在一些实施方式中，当所述第一电池单体、所述第二电池单体和所述第三电池单体中所述第一正极活性物质种类相同且所述正极功能助剂种类相同时，所述第一正极活性物质占正极活性物质的质量占比按照所述第一电池单体、所述第二电池单体、所述第三电池单体的顺 序递减，所述正极功能助剂占正极活性物质的质量占比按照所述第一电池单体、所述第二电池单体、所述第三电池单体的顺序递增。
用于产生放电电压较低的第二放电电压平台的正极功能助剂的质量占比越大，第二放电电压平台对应的放电容量占比越大，电池单体的低温能量保持率越高，通过使配置在第三区域中的第三电池单体的正极功能助剂的质量占比＞配置在第二区域中的第二电池单体的正极功能助剂的质量占比＞配置在第一区域中的第一电池单体的正极功能助剂的质量占比，能够使第三电池单体的低温能量保持率＞第二电池单体的低温能量保持率＞第一电池单体的低温能量保持率，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释放的能量大致一致，从而进一步提高电池包整体在低温下的能量保持率。
在一些实施方式中，在所述第一电池单体中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占96.0％-100％，所述正极功能助剂的质量占0％-4.0％。
由此，通过使第一电池单体中的第一正极活性物质和正极功能助剂的质量占比在上述范围内，能够使第一电池单体中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第一电池单体在低温下能够释放的能量，从而提升电池包整体的低温能量保持率。
在一些实施方式中，在所述第二电池单体中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占88.5％-96.0％，所述正极功能助剂的质量占4.0％-11.5％。
由此，通过使第二电池单体中的第一正极活性物质和正极功能助剂的质量占比在上述范围内，能够使第二电池单体中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第二电池单体在低温下能够释放的能量，从而进一步提升电池包整体的低温能量保持率。
在一些实施方式中，在所述第三电池单体中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占76.5％-88.5％，所述正极功能助剂的质量占11.5％-23.5％。
由此，通过使第三电池单体中的第一正极活性物质和正极功能助 剂的质量占比在上述范围内，能够使第三电池单体中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第三电池单体在低温下能够释放的能量，从而更进一步提升电池包整体的低温能量保持率。
在一些实施方式中，所述正极功能助剂为碳包覆的含锂元素的钛铌氧化物。
由此，通过对作为正极功能助剂的钛铌氧化物进行碳包覆和预锂化，能够提高钛铌氧化物的导电性和电池单体的有效锂离子数量，提高作为正极功能助剂的钛铌氧化物的结构稳定性，保证电池单体的能量密度和循环稳定性。
在一些实施方式中，所述第一电池单体、所述第二电池单体和所述第三电池单体各自的负极经过了补锂处理。
由此，通过对第一电池单体、第二电池单体和第三电池单体各自的负极进行补锂处理，能够弥补由于正极活性物质中添加钛铌氧化物导致的锂离子的不足，使电池单体的有效锂离子总量不降低，从而保证电池单体的能量密度。
在一些实施方式中，在0℃以下的温度下，所述第一电池单体的放电截止电压为1.4-1.6V，所述第二电池单体的放电截止电压为1.2-1.4V，所述第三电池单体的放电截止电压为1.0-1.2V。
由此，通过如上述那样设置第一电池单体、第二电池单体和第三电池单体的放电截止电压，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释放的能量大致一致，从而能够提高电池包整体在低温下的能量保持率。
在一些实施方式中，所述第一电池单体的数量∶所述第二电池单体的数量∶所述第三电池单体的数量＝(3-8)∶(8-13)∶(10-15)。换言之，当第一电池单体的数量、第二电池单体的数量和第三电池单体的数量之和为100％时，第一电池单体的数量占比大约为10-30％，第二电池单体的数量占比大约为25-50％，第三电池单体的数量占比大约为30-60％。
由此，只要按照常见的电池包的温度分布范围来设置第一电池单体、第二电池单体和第三电池单体的数量，就能够容易地实现本申请 的电池包。
本申请的第二方面提供一种用电装置，其包括本申请的第一方面的电池包。
由此，本申请的第二方面的用电装置在低温下的续航能力强，即使在低温下也能够长时间地正常使用。
发明效果
采用本发明，通过在电池包箱体内部的温度不同的区域配置具有双放电电压平台的低温能量保持率不同的电池单体，能够提供能够使温度不同的区域的电池单体在低温下释放的能量大致一致、整体在低温下的能量保持率提高的电池包和包括该电池包的用电装置。
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，该电池单体的正极活性物质由第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂钛铌氧化物(TNO，例如TiNb 2O 7)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，如果列出了最小范围值1和2，并且列出了最大范围值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2-5。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。
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，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。
于是，发明人想到，通过在电池包中温度较低的区域配置低温放电性能更优异的电池单体，能够使电池包中不同位置的电池单体在低温环境下放出的能量大致一致，从而使电池包整体在低温环境下的能量发挥得到提高，进而提升使用该电池包作为电源的用电装置在低温环境下的续航里程。
为了达到上述目的，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两个放电电压平台，在较高的放电电压平台放电结束之后，继续利用较低的放电电压平台进行放电，能够提高这些电池单体的放电量，从而使这些电池单体在低温下的放电性能更优异。
能够提供较低的放电电压平台的物质已知有多种，发明人通过反复研究发现，通常被用作负极活性物质的钛氧化物、铌氧化物或钛铌氧化物具有较低的对锂电位，当将这些物质作为正极功能助剂添加在常规正极活性物质中时，这些物质能够提供较低的放电电压平台，使得电池单体在低温下能够放出更多的能量，提高电池单体的放电量，进而提升电池包整体在低温下的能量保持率。
而且，在电池单体中的正极功能助剂的质量占正极活性物质的总质量(常规正极活性物质与正极功能助剂的质量之和)的比例不超过 一定比例(例如50％)的情况下，较低的放电电压平台对应的放电容量占高低两个放电电压平台对应的总放电容量的比例越高，电池单体的低温性能越优异。这样，通过在温度越低的区域使用较低的放电电压平台对应的放电容量占比越高的电池单体，能够使配置在温度不同的各个区域中的电池单体在低温下所发挥出的能量大致一致，能够提高电池包整体在低温下的能量保持率，从而提高使用该电池包作为电源的电动汽车等用电装置在低温下的续航能力。
电池包
下面，对本申请的电池包1进行具体说明。
图1是本申请一实施方式的电池包1的结构示意图。图2是图1所示的电池包1除去箱体后的结构组件的俯视图。
如图1和图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)。
如图2所示，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、二、三区域而画的虚拟线。
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。所述第一电池单体61、所述第二电池单体62和所述第三电池单体63各自具有第一放电电压平台和第二放电电压平台，所述第一放电电压平台的平均放电电压高于所述第二放电电压平台的平均放电电压。所述第一电池单体61、所述第二电池单体62和所述第三电池单体63 各自的正极活性物质由具有所述第一放电电压平台的第一正极活性物质和具有所述第二放电电压平台的正极功能助剂混合而成，所述正极功能助剂为钛氧化物、铌氧化物或钛铌氧化物。在所述第一电池单体61、所述第二电池单体62和所述第三电池单体63各自中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第三电池单体63的所述第二放电电压平台对应的放电容量占比＞所述第二电池单体62的所述第二放电电压平台对应的放电容量占比＞所述第一电池单体61的所述第二放电电压平台对应的放电容量占比。当置于同样温度的外界环境中时，在电池包1内，第三区域R3的温度低于第二区域R2的温度，第二区域R2的温度低于第一区域R1的温度。
需要特别说明的是，在本申请整个说明书中，尽管将第一电池单体描述为具有第一放电电压平台和第二放电电压平台，或将第一电池单体的正极活性物质描述为由具有第一放电电压平台的第一正极活性物质和具有第二放电电压平台的正极功能助剂混合而成，但仅包括第一放电电压平台、不包括第二电压放电平台的第一电池单体，即仅由第一正极活性物质形成的第一电池单体也在本发明的范围内。
需要说明的是，“放电电压平台”是放电曲线中放电电压比较平稳的部分，在放电电压平台进行放电时，单位时间的放电量较多。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，该电池单体的正极活性物质由第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂钛铌氧化物(TNO，例如TiNb 2O 7)组成。如图3所示，NCM的放电电压平台的下限为2.5V(图3中的A点)，TNO的放电电压平台的上限为1.8V(图3中的B点)。另外，如图3所示，在电池单体的放电曲线具有两个放电电压平台的情况下，经过A点之后，放电电压急剧下降，下降到B点之后又趋于平稳，继续利用放电电压平台进行放电。
在图3中，第一个电压瞬降结束的B点之前为第一放电电压平台(即高电压放电平台，也即本申请的第一放电电压平台)，其在数据值上等于高电压正极活性物质放出的所有能量与电流的比值(是一个均衡的值，也可以粗略看作B点之前的平均电压)，第一个电压瞬降结束 的B点之后成为第二放电电压平台(即低电压放电平台，也即本申请的第二放电电压平台)，体现为低电压正极活性物质(例如本申请中的正极功能助剂)放出的所有能量与电流的比值(是一个均衡的值，也可以粗略看作B点之后的平均电压)。
本申请中，在电池包箱体的内部空间的温度不同的区域中分别配置具有双放电电压平台(放电电压较高的第一放电电压平台和放电电压较低的第二放电电压平台)的低温能量保持率不同的电池单体61、62、63，并且在温度越低的区域配置低温能量保持率越高的电池单体。具体而言，按照通常的电池包内部的温度分布，第一区域R1的温度＞第二区域R2的温度＞第三区域R3的温度，在本申请中，第三电池单体63的第二放电电压平台对应的放电容量占比＞第二电池单体62的第二放电电压平台对应的放电容量占比＞第一电池单体61的第二放电电压平台对应的放电容量占比。
需要说明的是，本申请的第一/第二/第三电池单体的第二放电电压平台对应的放电容量占比的具体定义和测试方法参见本说明书“相关测试”部分。
在电池包中所处不同位置的电池单体，散热能力不同。通常，越靠外侧的电池单体，散热能力越强，即散热速度越快，随着从电池包外侧向电池包内部去，电池单体的散热速度逐渐降低；相反，随着从电池包内部向电池包外侧去，电池单体的保温能力逐渐降低。因此，电池包不同区域的电池单体的温度不同，导致其充放电性能不一致：例如，在低温外界环境下，内侧的电池单体散热速度相对较慢，温度相对较高，低温外界环境下的性能相对较好(但高温性能较差)；然而，外侧的电池单体散热速度相对较快，温度相对较低，低温外界环境下的性能相对较差(但高温性能较高)。由此，这种电池包内不同区域的电池单体在低温环境下出现的彼此之间电性能差异过大的现象，会使电池包整体在低温环境下的能量保持率降低。
为了解决上述问题，本申请发明人通过在温度不同的第一区域R1、第二区域R2和第三区域R3中设置具有双放电电压平台(即，放电电压相对较高的第一放电电压平台和放电电压相对较低的第二放电电压平台)的第一电池单体61、第二电池单体62和第三电池单体63，当 第一放电电压平台的放电结束后，能够再利用第二放电电压平台继续进行放电(即实现同一电池单体的梯次放电)，由此提高每个电池单体在低温环境下释放的能量，从而能够提高电池包整体的低温能量保持率。
本申请中具有双放电电压平台的第一电池单体61、第二电池单体62和第三电池单体63各自的正极活性物质由常规正极活性物质(第一正极活性物质)和正极功能助剂混合制备而成。常规正极活性物质具有放电电压较高的第一放电电压平台，正极功能助剂为具有ReO 3构型的层状结构的钛氧化物、铌氧化物或者钛铌氧化物，这些正极功能助剂具有放电电压较低的第二放电电压平台。电池单体中的放电电压较低的第二放电电压平台的放电容量，可通过改变正极活性物质中的正极功能助剂的含量来进行调节。
而且本申请发明人发现，通过进一步调节第一电池单体61、第二电池单体62和第三电池单体63的第二放电电压平台对应的放电容量占比，能够得到整体低温能量保持率更高的电池包1，并且这种设置显著改善了电池包在冬季的低温条件下的低温能量保持率。具体而言，通过使第三电池单体63的第二放电电压平台对应的放电容量占比＞第二电池单体62的第二放电电压平台对应的放电容量占比＞第一电池单体61的第二放电电压平台对应的放电容量占比，能够在第一电池单体61无法继续放电的低温环境下，使第二电池单体62和第三电池单体63继续放电，在第一电池单体61和第二电池单体62无法继续放电的低温环境下，使第三电池单体63继续放电，以确保电池包整体的放电容量处于较高水平。
本发明人进一步对设置在温度不同的各区域R1、R2、R3中的具有双放电电压平台的各电池单体61、61、63中的第二放电电压平台对应的放电容量占比与电池包-20℃总能量保持率之间的关系进行了深入研究。结果发现，在第一电池单体61、第二电池单体62和第三电池单体63各自中，当第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量之和为100％时，通过使第三电池单体63的第二放电电压平台对应的放电容量占比＞第二电池单体62的第二放电电压平台对应的放电容量占比＞第一电池单体61的第二放电电压平台对应的 放电容量占比，能够使第三电池单体63的低温能量保持率＞第二电池单体62的低温能量保持率＞第一电池单体61的低温能量保持率，能够使配置在电池包的温度不同的各区域R1、R2、R3中的各电池单体61、62、63在低温下能够释放出来的能量(在低温下的放电容量)大致一致，从而能够提高电池包1整体的低温能量保持率(电池包-20℃总能量保持率)，提高电池包整体在低温下的续航能力。
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，第一电池单体61、第二电池单体62和第三电池单体63中的所述正极功能助剂为由Ti 2Nb 2xO 4+5x表示的钛铌氧化物，其中x为1以上的整数，可选地，所述钛铌氧化物为选自Ti 2Nb 2O 9、TiNb 2O 7、Ti 2Nb 10O 29和TiNb 24O 62中的一种或多种。
钛铌氧化物一般是由不同比例的钛氧化物和铌氧化物化合制得，由于钛和铌原子半径相近，因此钛铌氧化物都具有ReO 3构型的层状结构，且钛离子和铌离子还具有相似的电化学特性，Nb 5+/Nb 4+、Nb 4+/Nb 3+和Ti 4+/Ti 3+的氧化还原电位相差较小，均在1-2V的范围内。
由此，通过选择性能优异的钛铌氧化物作为正极功能助剂，能够得到具有合适的第二放电电压平台的第一电池单体61、第二电池单体62和第三电池单体63，从而能够实现低温性能优异的本申请电池包。
上述的钛铌氧化物可通过市购获得，或者利用下述方法制备：按照Ti 2Nb 2xO 4+5x各元素配比，调整TiO 2和Nb 2O 5粉末质量比，加入溶剂，溶剂可以是乙醇、水或丙酮，混合物经球磨、干燥、加热、冷却，即可得到相应钛铌氧化物。
在一些实施方式中，所述第二放电电压平台的放电电压范围为1.0-2.0V，可选地，所述第二放电电压平台在1.2-1.6V的放电容量占所述第二放电电压平台的总放电容量的50％以上，可选为70％以上。
由此，通过使第二放电电压平台的放电电压在上述范围内，能够使第二放电电压平台的放电电压与第一放电电压平台的放电电压具有明显差异，能够显著地获得具有双放电电压平台所带来的上述效果。通过使第二放电电压平台在1.2-1.6V的放电容量占第二放电电压平台的总放电容量的比例在上述范围内，能够确保电池单体在低温下能够释放出足够的能量，从而确保电池包整体的低温能量保持率。
在一些实施方式中，在所述第一、第二、第三电池单体61、62、63中，所述第一放电电压平台的最低放电电压与所述第二放电电压平台的最高放电电压之差为0.5V以上，可选为1.0V以上。
参照图3，本申请所述的“第一放电电压平台的最低放电电压”是指A点对应的放电电压，所述的“第二放电电压平台的最高放电电压”是指B点对应的放电电压。
针对存在两个放电电压平台的电池单体，第一放电电压平台与第二放电电压平台的放电电压的差异越大，第二放电电压平台所带来的上述效果越显著。若第一放电电压平台的最低放电电压与第二放电电压平台的最高放电电压之差小于0.5V，则第一放电电压平台与第二放电电压平台的放电电压的差异较小，不能显著地获得第二放电电压平台所带来的上述效果。
通过使第一放电电压平台的最低放电电压与第二放电电压平台的最高放电电压之差在上述范围，能够利用放电电压较高的第一放电电压平台进行放电之后，继续利用放电电压较低的第二放电电压平台进行放电，能够显著提高各电池单体在低温下能够释放的能量，从而提升电池包整体在低温下的能量保持率。
在一些实施方式中，在所述第一电池单体61中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占90％-100％，所述第二放电电压平台对应的放电容量占0％-10％。其中，所述第一放电电压平台对应的放电容量占100％，所述第二放电电压平台对应的放电容量占0％，是指第一电池单体61仅具有一个放电电压平台的情形，其也在本发明的范围之内。
由此，通过使第一电池单体61中的第一放电电压平台对应的放电 容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第一电池单体61在低温下能够释放的能量，从而提升电池包1整体的低温能量保持率。
在一些实施方式中，在所述第二电池单体62中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占73％-95％，所述第二放电电压平台对应的放电容量占5％-27％。
由此，通过使第二电池单体62中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第二电池单体62在低温下能够释放的能量，从而进一步提升电池包1整体的低温能量保持率。
在一些实施方式中，在所述第三电池单体63中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占54％-87％，所述第二放电电压平台对应的放电容量占13％-46％。
由此，通过使第三电池单体63中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第三电池单体63在低温下能够释放的能量，从而更进一步提升电池包1整体的低温能量保持率。
在一些实施方式中，所述第一电池单体61的正极活性物质的克容量为148-285mAh/g，所述第二电池单体的正极活性物质的克容量为155-295mAh/g，所述第三电池单体的正极活性物质的克容量为169-311mAh/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第一正极活性物质和正极功能助剂各自的克容量和质量占比来计算。
在一些实施方式中，所述正极功能助剂的理论克容量为 350-410mAh/g。
由此，通过使用理论克容量在上述范围内的正极功能助剂，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，所述第一正极活性物质为选自锰酸锂、镍酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂和磷酸铁锂中的一种。
由此，只要由第一正极活性物质产生的第一放电电压平台与由正极功能助剂产生的第二放电电压平台的放电电压和放电容量占比满足上述关系，第一正极活性物质可以从现有的各种正极活性物质中选择，从而，能够利用现有的正极活性物质容易地实现本申请的电池包。
在一些实施方式中，当所述第一电池单体61、所述第二电池单体62和所述第三电池单体63中所述第一正极活性物质种类相同且所述正极功能助剂种类相同时，所述第一正极活性物质占正极活性物质的质量占比按照所述第一电池单体61、所述第二电池单体62、所述第三电池单体63的顺序递减，所述正极功能助剂占正极活性物质的质量占比按照所述第一电池单体61、所述第二电池单体62、所述第三电池单体63的顺序递增。
用于产生放电电压较低的第二放电电压平台的正极功能助剂的质量占比越大，第二放电电压平台对应的放电容量占比越大，电池单体的低温能量保持率越高，通过使配置在第三区域R3中的第三电池单体63的正极功能助剂的质量占比＞配置在第二区域R2中的第二电池单体62的正极功能助剂的质量占比＞配置在第一区域R1中的第一电池单体61的正极功能助剂的质量占比，能够使第三电池单体63的低温能量保持率＞第二电池单体62的低温能量保持率＞第一电池单体61的低温能量保持率，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在低温下释放的能量大致一致，从而提高电池包1整体在低温下的能量保持率。
在一些实施方式中，在所述第一电池单体61中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占96.0％-100％，所述正极功能助剂的质量占0％-4.0％。其中，所述第一正极活性物质的质量占100％，所述正极功能助剂的质量 占0％，是指第一电池单体61仅由第一正极活性物质形成的情形，其也在本发明的范围之内。
由此，通过使第一电池单体61中的第一正极活性物质和正极功能助剂的质量占比在上述范围内，能够使第一电池单体61中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第一电池单体61在低温下能够释放的能量，从而提升电池包1整体的低温能量保持率。
在一些实施方式中，在所述第二电池单体62中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占88.5％-96.0％，所述正极功能助剂的质量占4.0％-11.5％。
由此，通过使第二电池单体62中的第一正极活性物质和正极功能助剂的质量占比在上述范围内，能够使第二电池单体62中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第二电池单体62在低温下能够释放的能量，从而进一步提升电池包1整体的低温能量保持率。
在一些实施方式中，在所述第三电池单体63中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占76.5％-88.5％，所述正极功能助剂的质量占11.5％-23.5％。
由此，通过使第三电池单体63中的第一正极活性物质和正极功能助剂的质量占比在上述范围内，能够使第三电池单体63中的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量各自的占比在上述范围内，能够提高第三电池单体63在低温下能够释放的能量，从而进一步提升电池包1整体的低温能量保持率。
在一些实施方式中，所述正极功能助剂为碳包覆的含锂元素的钛铌氧化物。
由此，通过对作为正极功能助剂的钛铌氧化物这样的欠锂物质进行预锂化处理，能够补充由于常规正极活性物质的减少而导致的锂离子数量的减少，使得电池单体具有符合要求的锂离子数量，保证电池单体的能量密度。另外，通过对经过预锂化处理的钛铌氧化物进行碳包覆，能够提高钛铌氧化物的导电性。从而，能够提高作为正极功能助剂的钛铌氧化物的结构稳定性，保证电池单体的能量密度和循环稳 定性。
作为对钛铌氧化物进行预锂化的方法，可以采用公知的对欠锂物质进行预锂化的方法，例如，可以采用下述方法：将所制备的钛铌氧化物与碳酸锂混合后，压实放在氧化铝陶瓷坩埚中，置于高炉中升温到碳酸锂的熔融温度，冷却到室温取出进行球磨分散，得到预锂化的产物。通过对钛铌氧化物进行预锂化，能够提升电池首效。
作为对预锂化后的钛铌氧化物进行碳包覆的方法，可以采用公知的碳包覆方法，例如，可以采用下述方法：按照钛铌氧化物(Ti 2Nb 2xO 4+5x)各元素配比与所需的碳包覆量，调整预锂化后的钛铌氧化物与葡萄糖的质量比，加入溶剂，溶剂可以是乙醇、水或丙酮，混合液经球磨、干燥造粒、煅烧，即可得到碳包覆的含锂元素的钛铌氧化物材料。通过对预锂化后的钛铌氧化物进行碳包覆，能够提升钛铌氧化物的电导率。
在一些实施方式中，所述第一电池单体61、所述第二电池单体62和所述第三电池单体63各自的负极经过了补锂处理。
由此，通过对第一电池单体61、第二电池单体62和第三电池单体63各自的负极进行补锂处理，能够弥补由于正极活性物质中添加钛铌氧化物导致的锂离子的不足，使电池单体的有效锂离子总量不降低，从而保证电池单体的能量密度。
作为负极进行补锂处理的方法，可以采用公知的各种方法，例如，可以采用下述方法：(1)将粘结剂、锂粉和有机溶剂混合，可得锂粉溶液；(2)采用物理的方式将所述锂粉溶液涂敷于负极极片上；(3)负极极片经干燥、冷压，即可得到预锂化负极极片。通过进行负极补锂，能够提升电池首效。
正极功能助剂的预锂化处理和负极的补锂处理只要进行至少任一者即可。
在一些实施方式中，在0℃以下的温度下，所述第一电池单体的放电截止电压为1.4-1.6V，所述第二电池单体的放电截止电压为1.2-1.4V，所述第三电池单体的放电截止电压为1.0-1.2V。
由此，通过如上述那样设置第一电池单体61、第二电池单体62和第三电池单体63的放电截止电压，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在低温下释放的能量大致一致，从而能够提高电池包整体在低温下的能量保持率。
充电截止电压过高或者放电截止电压过低会损害电池单体的循环性能。在充电截止电压过高的情况下，电池单体会过充电，在电池单体电量已满的情况下继续充电会导致正极材料结构变化，造成容量损失，而正极材料分解放出的氧会与电解液发生剧烈的化学反应，最坏的结果有可能导致发生爆炸。在放电截止电压过低的情况下，电池单体会过放电，过放电会使电池单体内压升高，正负极活性物质可逆性受到破坏，即使充电也只能部分恢复，容量也会有明显衰减。电池单体深充深放，会增大电池单体的损耗，电池单体最理想的工作状态是浅充浅放，这样能够延长电池单体的寿命。
在一些实施方式中，所述第一电池单体61的数量∶所述第二电池单体62的数量∶所述第三电池单体63的数量＝(3-8)∶(8-13)∶(10-15)。换言之，当第一电池单体61的数量、第二电池单体62的数量和第三电池单体63的数量之和为100％时，第一电池单体61的数量占比大约为10-30％，第二电池单体62的数量占比大约为25-50％，第三电池单体63的数量占比大约为30-60％。
在一些实施方式，第一电池单体61的数量可以为1。
由此，只要按照常见的电池包的温度分布范围来设置第一电池单体61、第二电池单体62和第三电池单体63的数量，就能够容易地实现本申请的电池包。
用电装置
另外，本申请还提供一种用电装置，所述用电装置包括本申请的电池包。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。
(一)电池单体的制备
I.第一电池单体的制备
[制备例I-1]
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LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂TiNb 2O 7、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，正极功能助剂预先经过了预锂化和碳包覆，正极活性物质、导电炭黑、粘结剂PVDF的质量比为96∶2∶2，正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为2∶98。
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。
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。
[制备例I-2]
除了正极活性物质使用第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂TiO 2以外，与制备例I-1同样地操作，获得第一电池单体I-2。
[制备例I-3]
除了正极活性物质使用第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂Nb 2O 5以外，与制备例I-1同样地操作，获得第一电池单体I-3。
[制备例I-4]
除了正极活性物质使用第一正极活性物质磷酸铁锂(LFP)和正极功能助剂TiNb 2O 7以外，与制备例I-1同样地操作，获得第一电池单体I-4。
[制备例I-5]
除了正极活性物质使用第一正极活性物质锰酸锂(LMO)和正极功能助剂TiNb 2O 7以外，与制备例I-1同样地操作，获得第一电池单体I-5。
[制备例I-6]
除了正极活性物质使用第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2 (NCM)和正极功能助剂Ti 2Nb 2O 9以外，与制备例I-1同样地操作，获得第一电池单体I-6。
[制备例I-7]
除了正极活性物质使用第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂Ti 2Nb 10O 29以外，与制备例I-1同样地操作，获得第一电池单体I-7。
[制备例I-8]
除了正极活性物质使用第一正极活性物质LiNi 0.6Co 0.2Mn 0.2O 2(NCM)和正极功能助剂TiNb 24O 62以外，与制备例I-1同样地操作，获得第一电池单体I-8。
[制备例I-9]
除了正极活性物质使用第一正极活性物质磷酸铁锂(LFP)和正极功能助剂Ti 2Nb 2O 9以外，与制备例I-1同样地操作，获得第一电池单体I-9。
[制备例I-10]
除了正极活性物质使用第一正极活性物质锰酸锂(LMO)和正极功能助剂Ti 2Nb 10O 29以外，与制备例I-1同样地操作，获得第一电池单体I-10。
[制备例I-11]
除了正极活性物质仅使用NCM以外，与制备例I-1同样地操作，获得第一电池单体I-11。
[制备例I-12]
除了正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-1同样地操作，获得第一电池单体I-12。
[制备例I-13]
除了正极活性物质仅使用LFP以外，与制备例I-1同样地操作，获得第一电池单体I-13。
[制备例I-14]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LFP的质量比为4∶96以外，与制备例I-4同样地操作，获得第一电池单体I-14。
II.第二电池单体的制备
[制备例II-1]
除了正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为6.5∶93.5以外，与制备例I-1同样地操作，获得第二电池单体II-1。
[制备例II-2]
除了正极功能助剂TiO 2与第一正极活性物质NCM的质量比为6.5∶93.5以外，与制备例I-2同样地操作，获得第二电池单体II-2。
[制备例II-3]
除了正极功能助剂Nb 2O 5与第一正极活性物质NCM的质量比为6.5∶93.5以外，与制备例I-3同样地操作，获得第二电池单体II-3。
[制备例II-4]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LFP的质量比为6.5∶93.5以外，与制备例I-4同样地操作，获得第二电池单体II-4。
[制备例II-5]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LMO的质量比为6.5∶93.5以外，与制备例I-5同样地操作，获得第二电池单体II-5。
[制备例II-6]
除了正极功能助剂Ti 2Nb 2O 9与第一正极活性物质NCM的质量比为6.5∶93.5以外，与制备例I-6同样地操作，获得第二电池单体II-6。
[制备例II-7]
除了正极功能助剂Ti 2Nb 10O 29与第一正极活性物质NCM的质量比为6.5∶93.5以外，与制备例I-7同样地操作，获得第二电池单体II-7。
[制备例II-8]
除了正极功能助剂TiNb 24O 62与第一正极活性物质NCM的质量比为6.5∶93.5以外，与制备例I-8同样地操作，获得第二电池单体II-8。
[制备例II-9]
除了正极功能助剂Ti 2Nb 2O 9与第一正极活性物质LFP的质量比为6.5∶93.5以外，与制备例I-9同样地操作，获得第二电池单体II-9。
[制备例II-10]
除了正极功能助剂Ti 2Nb 10O 29与第一正极活性物质LMO的质量比为6.5∶93.5以外，与制备例I-10同样地操作，获得第二电池单体II-10。
[制备例II-11]
与制备例I-11同样地操作，获得第二电池单体II-11。
[制备例II-12]
除了正极活性物质仅使用LFP以外，与制备例I-1同样地操作，获得第二电池单体II-12。
[制备例II-13]
与制备例I-1同样地操作，获得第二电池单体II-13。
[制备例II-14]
除了正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为4∶96以外，与制备例I-1同样地操作，获得第二电池单体II-14。
[制备例II-15]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LFP的质量比为 11.5∶88.5以外，与制备例I-4同样地操作，获得第二电池单体II-15。
[制备例II-16]
除了正极活性物质使用第一正极活性物质锰酸锂(LMO)和正极功能助剂Ti 2Nb 2O 9、且正极功能助剂Ti 2Nb 2O 9与第一正极活性物质LMO的质量比为11.5∶88.5以外，与制备例I-1同样地操作，获得第二电池单体II-16。
[制备例II-17]
除了正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为20∶80以外，与制备例I-1同样地操作，获得第二电池单体II-17。
III.第三电池单体的制备
[制备例III-1]
除了正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-1同样地操作，获得第三电池单体III-1。
[制备例III-2]
除了正极功能助剂TiO 2与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-2同样地操作，获得第三电池单体III-2。
[制备例III-3]
除了正极功能助剂Nb 2O 5与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-3同样地操作，获得第三电池单体III-3。
[制备例III-4]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LFP的质量比为11.5∶88.5以外，与制备例I-4同样地操作，获得第三电池单体III-4。
[制备例III-5]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LMO的质量比为11.5∶88.5以外，与制备例I-5同样地操作，获得第三电池单体III-5。
[制备例III-6]
除了正极功能助剂Ti 2Nb 2O 9与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-6同样地操作，获得第三电池单体III-6。
[制备例III-7]
除了正极功能助剂Ti 2Nb 10O 29与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-7同样地操作，获得第三电池单体III-7。
[制备例III-8]
除了正极功能助剂TiNb 24O 62与第一正极活性物质NCM的质量比为11.5∶88.5以外，与制备例I-8同样地操作，获得第三电池单体III-8。
[制备例III-9]
除了正极功能助剂Ti 2Nb 2O 9与第一正极活性物质LFP的质量比为11.5∶88.5以外，与制备例I-9同样地操作，获得第三电池单体III-9。
[制备例III-10]
除了正极功能助剂Ti 2Nb 10O 29与第一正极活性物质LMO的质量比为11.5∶88.5以外，与制备例I-10同样地操作，获得第三电池单体III-10。
[制备例III-11]
与制备例I-11同样地操作，获得第三电池单体III-11。
[制备例III-12]
除了正极活性物质仅使用LMO以外，与制备例I-1同样地操作，获得第三电池单体III-12。
[制备例III-13]
与制备例I-1同样地操作，获得第三电池单体III-13。
[制备例III-14]
除了正极功能助剂TiNb 2O 7与第一正极活性物质NCM的质量比为23.5∶76.5以外，与制备例I-1同样地操作，获得第三电池单体III-14。
[制备例III-15]
除了正极功能助剂TiNb 2O 7与第一正极活性物质LFP的质量比为23.5∶76.5以外，与制备例I-4同样地操作，获得第三电池单体III-15。
[制备例III-16]
除了正极功能助剂Ti 2Nb 2O 9与第一正极活性物质LMO的质量比为23.5∶76.5以外，与制备例II-16同样地操作，获得第三电池单体III-16。
(二)电池包的组装
[实施例1]
如图2所示，电池包箱体的内部空间划分为第一区域R1、第二区域R2和第三区域R3，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。
[实施例2]
除了使用第一电池单体I-2代替第一电池单体I-1，使用第二电池单体II-2代替第二电池单体II-1，使用第三电池单体III-2代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例3]
除了使用第一电池单体I-3代替第一电池单体I-1，使用第二电池单体II-3代替第二电池单体II-1，使用第三电池单体III-3代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例4]
除了使用第一电池单体I-4代替第一电池单体I-1，使用第二电池 单体II-4代替第二电池单体II-1，使用第三电池单体III-4代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例5]
除了使用第一电池单体I-5代替第一电池单体I-1，使用第二电池单体II-5代替第二电池单体II-1，使用第三电池单体III-5代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例6]
除了使用第一电池单体I-6代替第一电池单体I-1，使用第二电池单体II-6代替第二电池单体II-1，使用第三电池单体III-6代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例7]
除了使用第一电池单体I-7代替第一电池单体I-1，使用第二电池单体II-7代替第二电池单体II-1，使用第三电池单体III-7代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例8]
除了使用第一电池单体I-8代替第一电池单体I-1，使用第二电池单体II-8代替第二电池单体II-1，使用第三电池单体III-8代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例9]
除了使用第一电池单体I-9代替第一电池单体I-1，使用第二电池单体II-9代替第二电池单体II-1，使用第三电池单体III-9代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例10]
除了使用第一电池单体I-10代替第一电池单体I-1，使用第二电池单体II-10代替第二电池单体II-1，使用第三电池单体III-10代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例11]
除了使用第一电池单体I-11代替第一电池单体I-1，使用第二电池单体II-14代替第二电池单体II-1外，与实施例1同样地操作，组装成电池包。
[实施例12]
除了使用第一电池单体I-11代替第一电池单体I-1，使用第二电池单体II-14代替第二电池单体II-1，使用第三电池单体III-14代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例13]
除了使用第一电池单体I-13代替第一电池单体I-1，使用第二电池单体II-15代替第二电池单体II-1，使用第三电池单体III-15代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例14]
除了使用第一电池单体I-14代替第一电池单体I-1，使用第二电池单体II-16代替第二电池单体II-1，使用第三电池单体III-16代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例15]
除了使用第一电池单体I-12代替第一电池单体I-1，使用第二电池单体II-17代替第二电池单体II-1，使用第三电池单体III-14代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[实施例16]
与实施例1同样地操作，组装成电池包。
[实施例17]
与实施例1同样地操作，组装成电池包。
[实施例18]
与实施例1同样地操作，组装成电池包。
[实施例19]
与实施例1同样地操作，组装成电池包。
[对比例1]
除了使用第一电池单体I-11代替第一电池单体I-1，使用第二电池单体II-11代替第二电池单体II-1，使用第三电池单体III-11代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[对比例2]
除了使用第一电池单体I-11代替第一电池单体I-1，使用第二电池单体II-12代替第二电池单体II-1，使用第三电池单体III-12代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[对比例3]
除了使用第二电池单体II-13代替第二电池单体II-1，使用第三电池单体III-13代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
[对比例4]
除了使用第一电池单体I-12代替第一电池单体I-1，使用第三电池单体III-13代替第三电池单体III-1以外，与实施例1同样地操作，组装成电池包。
需要说明的是，虽然在本申请的实施例中，电池包箱体的内部空间被划分为第一区域、第二区域和第三区域，但是本申请的电池包并不仅限于将电池包箱体的内部空间划分为3个区域的情况，也可以是除了第一区域、第二区域和第三区域以外，在第三区域的外侧还具有一个或多个区域，只要配置在外侧的区域中的电池单体包围配置在其内侧的区域中的电池单体的周围排布即可。
在电池包箱体的内部空间包括如上所述的3个以上的区域的情况下，只要满足越靠外侧的区域中，电池单体的第二放电电压平台对应的放电容量占比越高(即，电池单体的正极活性物质中的正极功能助剂的质量占比越高)即可。
另外，在电池包箱体的内部空间为矩形形状的情况下，可以是将该矩形形状的四个角作为最外侧的区域，在该区域中，电池单体的第二放电电压平台对应的放电容量占比最高(即，电池单体的正极活性物质中的正极功能助剂的质量占比最高)。
(三)相关测试
1、电池单体第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量的测定
对实施例1-19和对比例1-4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25℃时第一电池单体、第二电池单体和第三电池单体各自的第一放电电压平台对应的放电容量和第二放电电压平台对应的放电容量，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第二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℃以0.33C将电池单体充电至下述的表1所示的充电截止电压后，继续以该充电截止电压进行恒压充电，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℃以0.33C将电池单体放电至下述的表1所示的放电截止电压，记录电池单体放出的总放电容量C0；
(5)得出步骤(4)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，B点前的放电容量合计为第一放电电压平台对应的放电容量C1，B点至放电截止电压的放电容量为第二放电电压平台对应的放电容量C2。
因此，电池单体的第一放电电压平台对应的放电容量占比＝C1/C0， 电池单体的第二放电电压平台对应的放电容量占比＝C2/C0。
[表1]
正极活性物质种类 充电截止电压(V) 放电截止电压(V)
NCM+TiNb 2O 7 4.40 1.45
NCM+TiO 2 4.40 1.45
NCM+Nb 2O 5 4.40 1.45
LFP+TiNb 2O 7 3.80 1.45
LMO+TiNb 2O 7 4.40 1.45
NCM+Ti 2Nb 2O 9 4.40 1.45
NCM+Ti 2Nb 10O 29 4.40 1.45
NCM+TiNb 24O 62 4.40 1.45
LFP+Ti 2Nb 2O 9 3.80 1.45
LMO+Ti 2Nb 10O 29 4.40 1.45
LMO+Ti 2Nb 2O 9 4.40 1.45
2、电池包-20℃总能量保持率的测定
另外，对实施例1-19和对比例1-4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-20℃总满放能量，用电池包-20℃总满放能量除以电池包25℃总满放能量，计算出电池包-20℃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-20℃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。将实施例1-19和对比例1-4的各电池包的组成和测试结果示于下述的表2-表4。
Figure PCTCN2022096790-appb-000001
根据上述表2的结果可知，在实施例1-10中，第一电池单体、第二电池单体和第三电池单体均具有第一放电电压平台和第二放电电压平台，并且，第三电池单体的第二放电电压平台对应的放电容量占比＞第二电池单体的第二放电电压平台对应的放电容量占比＞第一电池单体的第二放电电压平台对应的放电容量占比，电池包-20℃总能量保持率达到65.0％-76.7％。
而在对比例1和对比例2中，第一电池单体、第二电池单体和第三电池单体都仅具有一个放电电压平台，电池包-20℃总能量保持率仅为60.5％和56.7％。
在对比例3中，虽然第一电池单体、第二电池单体和第三电池单体均具有第一放电电压平台和第二放电电压平台，但是，第一电池单体、第二电池单体和第三电池单体中的第二放电电压平台对应的放电容量占比相同，电池包-20℃总能量保持率仅为62.9％。
在对比例4中，虽然第一电池单体、第二电池单体和第三电池单体均具有第一放电电压平台和第二放电电压平台，但是，第三电池单体的第二放电电压平台对应的放电容量占比＜第二电池单体的第二放电电压平台对应的放电容量占比＜第一电池单体的第二放电电压平台的放电容量占比，电池包-20℃总能量保持率仅为60.7％。
Figure PCTCN2022096790-appb-000002
根据上述表3的结果可知，在实施例1、11-14中，第二电池单体和第三电池单体均具有第一放电电压平台和第二放电电压平台，第三电池单体的第二放电电压平台对应的放电容量占比＞第二电池单体的第二放电电压平台对应的放电容量占比＞第一电池单体的第二放电电压平台对应的放电容量占比，并且，第一电池单体、第二电池单体和第三电池单体各自中的正极功能助剂的质量占比和第二放电电压平台对应的放电容量占比在本申请中记载的优选范围内，电池包-20℃总能量保持率达到64.1％-70.0％。
而在实施例15中，第一电池单体和第二电池单体各自中的正极功能助剂的质量占比和/或第二放电电压平台对应的放电容量占比在本申请中记载的优选范围以外，电池包-20℃总能量保持率为59.3％。
Figure PCTCN2022096790-appb-000003
根据上述表4的结果可知，在实施例1中，第一电池单体、第二电池单体和第三电池单体均具有第一放电电压平台和第二放电电压平台，第三电池单体的第二放电电压平台对应的放电容量占比＞第二电池单体的第二放电电压平台对应的放电容量占比＞第一电池单体的第二放电电压平台对应的放电容量占比，并且，-20℃时第一电池单体、第二电池单体和第三电池单体的放电截止电压均在本申请中记载的优选范围内，电池包-20℃总能量保持率达到70％。
而在实施例16中，-20℃时第二电池单体和第三电池单体的放电截止电压过高，电池包-20℃总能量保持率为55％，这表明了截止电压对-20℃总能量保持率影响很大。
在实施例17中，第一电池单体和第二电池单体的放电截止电压过低，虽然电池包-20℃总能量保持率为71％，但是，当截止电压过低时，能够提高-20℃总能量保持率，相当于过放电，但是会导致电池单体性能恶化产生气体，影响电池单体寿命。
在实施例18中，-20℃时第二电池单体的放电截止电压过高，且大于第一电池单体的放电截止电压，电池包-20℃总能量保持率为62％。
在实施例19中，-20℃时第一电池单体的放电截止电压过低，第三电池单体的放电截止电压过高，且第三电池单体的放电截止电压＞第二电池单体的放电截止电压＞第一电池单体的放电截止电压，电池包-20℃总能量保持率为58％。
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 (20)

  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，
    所述电池包箱体的内部空间包括第一区域、第二区域和第三区域，在所述第一区域中配置有第一电池单体，在所述第二区域中配置有第二电池单体，在所述第三区域中配置有第三电池单体，所述第二电池单体包围所述第一电池单体的周围排布，所述第三电池单体包围所述第二电池单体的周围排布，其中，
    所述第一电池单体、所述第二电池单体和所述第三电池单体各自具有第一放电电压平台和第二放电电压平台，所述第一放电电压平台的平均放电电压高于所述第二放电电压平台的平均放电电压，
    所述第一电池单体、所述第二电池单体和所述第三电池单体各自的正极活性物质由具有所述第一放电电压平台的第一正极活性物质和具有所述第二放电电压平台的正极功能助剂混合而成，
    所述正极功能助剂为钛氧化物、铌氧化物或钛铌氧化物，
    在所述第一电池单体、所述第二电池单体和所述第三电池单体各自中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第三电池单体的所述第二放电电压平台对应的放电容量占比＞所述第二电池单体的所述第二放电电压平台对应的放电容量占比＞所述第一电池单体的所述第二放电电压平台对应的放电容量占比。
  2. 根据权利要求1所述的电池包，其特征在于，
    所述电池包箱体的所述内部空间由所述第一区域、所述第二区域和所述第三区域组成。
  3. 根据权利要求1或2所述的电池包，其特征在于，
    所述正极功能助剂为由Ti2Nb 2xO 4+5x表示的钛铌氧化物，其中x为1以上的整数，可选地，所述钛铌氧化物为选自Ti 2Nb 2O 9、TiNb 2O 7、Ti 2Nb 10O 29和TiNb 24O 62中的一种或多种。
  4. 根据权利要求1-3中任一项所述的电池包，其特征在于，
    所述第二放电电压平台的放电电压范围为1.0-2.0V，可选地，所述第二放电电压平台在1.2-1.6V的放电容量占所述第二放电电压平台的总放电容量的50％以上，可选为70％以上。
  5. 根据权利要求1-4中任一项所述的电池包，其特征在于，
    在所述第一、第二、第三电池单体中，所述第一放电电压平台的最低放电电压与所述第二放电电压平台的最高放电电压之差为0.5V以上，可选为1.0V以上。
  6. 根据权利要求1-5中任一项所述的电池包，其特征在于，
    在所述第一电池单体中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占90％-100％，所述第二放电电压平台对应的放电容量占0％-10％。
  7. 根据权利要求1-6中任一项所述的电池包，其特征在于，
    在所述第二电池单体中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占73％-95％，所述第二放电电压平台对应的放电容量占5％-27％。
  8. 根据权利要求1-7中任一项所述的电池包，其特征在于，
    在所述第三电池单体中，当所述第一放电电压平台对应的放电容量和所述第二放电电压平台对应的放电容量之和为100％时，所述第一放电电压平台对应的放电容量占54％-87％，所述第二放电电压平台对应的放电容量占13％-46％。
  9. 根据权利要求1-8中任一项所述的电池包，其特征在于，
    所述第一电池单体的正极活性物质的克容量为148-285mAh/g，所述第二电池单体的正极活性物质的克容量为155-295mAh/g，所述第三 电池单体的正极活性物质的克容量为169-311mAh/g。
  10. 根据权利要求1-9中任一项所述的电池包，其特征在于，
    所述正极功能助剂的理论克容量为350-410mAh/g。
  11. 根据权利要求1-10中任一项所述的电池包，其特征在于，
    所述第一正极活性物质为选自锰酸锂、镍酸锂、钴酸锂、镍钴锰酸锂、镍钴铝酸锂和磷酸铁锂中的一种。
  12. 根据权利要求1-11中任一项所述的电池包，其特征在于，
    当所述第一电池单体、所述第二电池单体和所述第三电池单体中所述第一正极活性物质种类相同且所述正极功能助剂种类相同时，所述第一正极活性物质占正极活性物质的质量占比按照所述第一电池单体、所述第二电池单体、所述第三电池单体的顺序递减，所述正极功能助剂占正极活性物质的质量占比按照所述第一电池单体、所述第二电池单体、所述第三电池单体的顺序递增。
  13. 根据权利要求1-12中任一项所述的电池包，其特征在于，
    在所述第一电池单体中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占96.0％-100％，所述正极功能助剂的质量占0％-4.0％。
  14. 根据权利要求1-13中任一项所述的电池包，其特征在于，
    在所述第二电池单体中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占88.5％-96.0％，所述正极功能助剂的质量占4.0％-11.5％。
  15. 根据权利要求1-14中任一项所述的电池包，其特征在于，
    在所述第三电池单体中，当所述第一正极活性物质和所述正极功能助剂的总质量为100％时，所述第一正极活性物质的质量占76.5％-88.5％，所述正极功能助剂的质量占11.5％-23.5％。
  16. 根据权利要求1-15中任一项所述的电池包，其特征在于，
    所述正极功能助剂为碳包覆的含锂元素的钛铌氧化物。
  17. 根据权利要求1-15中任一项所述的电池包，其特征在于，
    所述第一电池单体、所述第二电池单体和所述第三电池单体各自的负极经过了补锂处理。
  18. 根据权利要求1-17中任一项所述的电池包，其特征在于，
    在0℃以下的温度下，所述第一电池单体的放电截止电压为1.4-1.6V，所述第二电池单体的放电截止电压为1.2-1.4V，所述第三电池单体的放电截止电压为1.0-1.2V。
  19. 根据权利要求1-18中任一项所述的电池包，其特征在于，
    所述第一电池单体的数量∶所述第二电池单体的数量∶所述第三电池单体的数量＝(3-8)∶(8-13)∶(10-15)。
  20. 一种用电装置，其特征在于，包括权利要求1-19中任一项所述的电池包。
PCT/CN2022/096790 2022-06-02 2022-06-02 电池包和用电装置 WO2023230978A1 (zh)

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