WO2024011454A1 - 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
WO2024011454A1
WO2024011454A1 PCT/CN2022/105501 CN2022105501W WO2024011454A1 WO 2024011454 A1 WO2024011454 A1 WO 2024011454A1 CN 2022105501 W CN2022105501 W CN 2022105501W WO 2024011454 A1 WO2024011454 A1 WO 2024011454A1
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Prior art keywords
battery cell
discharge voltage
battery
discharge
voltage platform
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PCT/CN2022/105501
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English (en)
French (fr)
Inventor
朱畅
刘宏宇
别常峰
欧阳少聪
许宝云
谢庭祯
付成华
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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 PCT/CN2022/105501 priority Critical patent/WO2024011454A1/zh
Publication of WO2024011454A1 publication Critical patent/WO2024011454A1/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
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • 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
    • H01M50/50—Current conducting connections for cells or batteries
    • H01M50/572—Means for preventing undesired use or discharge
    • H01M50/584—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries
    • H01M50/59—Means for preventing undesired use or discharge for preventing incorrect connections inside or outside the batteries characterised by the protection means
    • H01M50/593—Spacers; Insulating plates
    • 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 stored in the battery pack box.
  • the internal space of the battery pack box is composed of i 1 , i 2 ,..., i n are composed of n areas in total, n is a positive integer greater than or equal to 2, among which the i (m-1) area is configured with the i (m-1) battery cell, and the i m
  • the i- th battery cell is arranged in the area, and the i- th battery cell is arranged around the i (m-1) -th battery cell.
  • m takes a value greater than 1 and less than or equal to n in sequence.
  • the i (m-1) th battery cell and the i m -th 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 high
  • the positive active material of each of the i (m-1) th battery cell and the i m -th battery cell is composed of the first discharge voltage platform.
  • a positive electrode active material is mixed with a positive electrode functional additive having the second discharge voltage platform, and the positive electrode functional additive is lithium vanadium oxide, in the i (m-1) battery cell and the In each of the i- th battery cells, 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%, all of the i- th battery cells.
  • the proportion of discharge capacity corresponding to the second discharge voltage platform > the proportion of discharge capacity corresponding to the second discharge voltage platform of the i (m-1) th battery cell.
  • 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.
  • Discharge voltage platform the positive electrode functional additive is lithium vanadium 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 battery pack includes a battery pack box and battery cells accommodated in the battery pack box.
  • the internal space of the battery pack box is composed of a first area, a second area and a third area. Composed of three regions, a first battery cell is configured in the first region, a second battery cell is configured in the second region, and a third battery cell is configured in the third region, so The second battery cells are arranged around the first battery cells, the third battery cells are arranged around the second battery cells, and the first battery cells and the third battery cells are arranged around the second battery cells.
  • 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 average discharge voltage of the second discharge voltage platform.
  • the positive electrode 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 and the second positive electrode active material having the second discharge voltage platform.
  • the positive electrode functional additive of the discharge voltage platform is mixed, and the positive functional additive is lithium vanadium oxide, in each of the first battery cell, the second battery cell and the third battery cell.
  • the shape of the battery pack described in this application is arbitrary and can be any shape designed according to customer requirements.
  • the positive electrode functional additive is lithium vanadium oxide represented by j(Li 2 O) ⁇ kVO x , where 1 ⁇ x ⁇ 2.5, j>0, k>0, optionally,
  • the lithium vanadium oxide is selected from the group consisting of LiVO 3 , Li 3 V 2 O 5 , Li 4 V 3 O 8 , LiV 3 O 8 , Li 2 VO 3 , LiVO 2 , Li 6 V 5 O 15 , LiV 2 O 5 and One or more types of Li 3 VO 4 .
  • lithium vanadium 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 lowest discharge voltage of the first discharge voltage platform and the highest discharge of the second discharge voltage platform are The voltage difference is above 0.5V, optionally above 1.0V.
  • the third 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 more than 0.5V, optionally more than 1.0V.
  • 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 internal space of the battery pack box is composed of a first area, a second area and a third area, in the first battery cell
  • the first discharge voltage platform corresponds to
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 88.2% to 100%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 88.2% to 100%.
  • Capacity accounts for 0% to 11.8%.
  • 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 internal space of the battery pack box is composed of a first area, a second area and a third area, in the second battery cell
  • the first discharge voltage platform corresponds to
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 72.1% to 96.1%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 72.1% to 96.1%.
  • Capacity accounts for 3.9% to 27.4%.
  • 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 internal space of the battery pack box is composed of a first area, a second area and a third area, in the third battery cell
  • the first discharge voltage platform corresponds to
  • the discharge capacity corresponding to the first discharge voltage platform accounts for 53.1% to 89.6%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 53.1% to 89.6%.
  • Capacity accounts for 10.4% ⁇ 46.9%.
  • 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 cell is 148-285 mAh/ g.
  • the gram capacity of the positive electrode active material of the second battery cell is 155-295 mAh/g, and the gram capacity of the positive electrode active material of the third battery cell is 169-311 mAh/g.
  • the theoretical gram capacity of the positive electrode functional additive is 275.8-477 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 The mass proportion of the first cathode active material to the cathode active material in the i (m-1) battery cell is greater than the mass proportion of the first cathode active material to the cathode active material in the i ( m -1) battery cell.
  • the mass proportion of the positive electrode functional additive in the positive electrode active material in the i (m-1) th battery cell is smaller than the mass proportion of the positive electrode functional additive in the positive electrode active material in the i ( m -1)th battery cell proportion.
  • the mass proportion of functional additives can make the low-temperature energy retention rate of the i- th battery cell > the low-temperature energy retention rate of the i-th (m-1) battery cell >, and can make the i-th (m-1) battery cell
  • the energy released by the battery cells at low temperatures is roughly the same as that of the i- th battery cell, that is, the energy released by the battery cells in the n regions in the battery pack at low temperature can be roughly consistent, thereby further improving the overall battery pack. Energy retention at low temperatures.
  • the internal space of the battery pack box is composed of a first area, a second area and a third area
  • the first battery cell, the second battery cell and the first cathode active material in the third battery cell is of the same type and the cathode functional additive is of the same type
  • the mass proportion of the first cathode active material to the cathode active material is based on the first battery cell
  • the order of the second battery cell and the third battery cell decreases
  • the mass proportion of the positive electrode functional additive to the cathode active material is in accordance with the first battery cell, the second battery cell,
  • the order of the third battery cells increases.
  • the mass proportion of the positive electrode functional additive of the first battery cell in the area can make the low-temperature energy retention rate of the third battery cell > the low-temperature energy retention rate of the second battery cell > the low-temperature energy of the first battery cell.
  • the retention rate can make the energy released by the first battery cell, the second battery cell and the third battery cell at low temperatures approximately consistent, thereby further improving the energy retention rate of the entire battery pack at low temperatures.
  • the internal space of the battery pack box is composed of a first region, a second region and a third region, in the first battery cell, when the first positive electrode active material and When the total mass of the positive electrode functional additives is 100%, the mass of the first positive electrode active material accounts for 96.0% to 100%, and the mass of the positive electrode functional additives accounts for 0% to 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 internal space of the battery pack box is composed of a first region, a second region and a third region, in the second battery cell, when the first positive electrode active material and When the total mass of the positive electrode functional additives is 100%, the mass of the first positive electrode active material accounts for 89.5% to 96.0%, and the mass of the positive electrode functional additives accounts for 4.0% to 10.5%.
  • 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 internal space of the battery pack box is composed of a first area, a second area and a third area, in the third battery cell, when the first positive electrode active material and When the total mass of the positive electrode functional additives is 100%, the mass of the first positive electrode active material accounts for 78.5% to 89.5%, and the mass of the positive electrode functional additives accounts for 10.5% to 21.5%.
  • 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 carbon-coated lithium vanadium oxide.
  • the conductivity of the lithium vanadium oxide as the positive electrode functional additive can be improved, thereby helping to improve the energy density and cycle stability of the battery cell. sex.
  • the discharge cut-off voltage of the first battery cell is 1.6-1.8V
  • the discharge cut-off voltage of the third battery cell is 1.4-1.6V.
  • 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 sum of the number of first battery cells, the number of second battery cells and the number of third battery cells is 100%, the number of first battery cells accounts for approximately 10% to 30%, and the number of third battery cells accounts for approximately 10% to 30%.
  • the number of second battery cells accounts for approximately 25-50%, and 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.
  • Figure 3 is a constant current discharge curve diagram of a battery cell with dual discharge voltage platforms.
  • the curve in the figure represents a battery cell with a first discharge voltage platform and a second discharge voltage platform in a battery pack according to an embodiment of the present application.
  • the constant current discharge curve of the body is a constant current discharge curve diagram of a battery cell with dual discharge voltage platforms.
  • 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. Additionally, if the minimum range values 1 and 2 are listed, and the maximum range values 3, 4, and 5 are listed, then the following ranges are all expected: 1 to 3, 1 to 4, 1 to 5, 2 to 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.
  • lithium vanadium oxide has a lower potential against lithium.
  • lithium vanadium oxide is added to conventional cathode active materials as a cathode functional additive, it can provide a lower discharge voltage platform, allowing the battery cells to release more energy at low temperatures and increase the discharge capacity of the battery cells. , thereby improving the overall energy retention rate of the battery pack 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.
  • the present application provides a battery pack, which includes a battery pack box and battery cells stored in the battery pack box.
  • the internal space of the battery pack box is composed of i 1 , i 2 ,..., in It consists of a total of n regions, n is a positive integer greater than or equal to 2 (for example, n is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12), among which the i (m-1) region
  • n is 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12
  • the i- th (m-1) battery cell is configured in
  • the i- th battery cell is configured in the i -th area
  • the i- th battery cell surrounds the i-th (m-1) battery cell.
  • m takes every positive integer greater than 1 and less than or equal to n in turn, the i (m-1) th battery cell and the i mth battery cell each have a first discharge voltage platform and a Two discharge voltage platforms, the average discharge voltage of the first discharge voltage platform is higher than the average discharge voltage of the second discharge voltage platform, the i (m-1) th battery cell and the i mth battery cell
  • Each cathode active material is mixed with a first cathode active material having the first discharge voltage platform and a cathode functional additive having the second discharge voltage platform, and the cathode functional additive is lithium vanadium oxide , in each of the i (m-1) -th battery cell and the i- th battery cell, when the discharge capacity corresponding to the first discharge voltage platform and the discharge capacity corresponding to the second discharge voltage platform When the sum is 100%, the proportion of discharge capacity corresponding to the second discharge voltage platform of the i- th battery cell > the second discharge voltage platform of the i-th (m-1)
  • 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 positive active material of each of the first battery cell 61 , the second battery cell 62 and the third battery cell 63 is composed of the first positive 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 lithium vanadium 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.
  • discharge voltage platform is the part of the discharge curve where the discharge voltage is relatively stable. When discharging at the discharge voltage platform, the discharge amount per unit time is larger.
  • the constant current discharge curve of a battery cell with dual discharge voltage platforms This discharge curve has two discharge voltage platforms. After passing point A, the discharge voltage drops sharply, and after falling to point B, it tends to Stable, continue to use the discharge voltage platform for discharge.
  • the point B where the first voltage drop ends is preceded by the first discharge voltage platform (i.e., the high voltage discharge platform, i.e., the first discharge voltage platform in this application), which is equal to the high voltage in terms of data value.
  • the ratio of all the energy released by the positive active material to the current (a balanced value, which can also be roughly regarded as the average voltage before point B).
  • the second discharge voltage platform i.e.
  • the low-voltage discharge platform that is, the second discharge voltage platform in this application
  • the low-voltage discharge platform 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, It can also 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; however, the outer battery cells dissipate heat relatively quickly and have a relatively low temperature, so the performance in low-temperature external environments is relatively poor. 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.
  • the conventional cathode active material has a first discharge voltage platform with a higher discharge voltage
  • the cathode functional additive is lithium vanadium oxide
  • the cathode functional additive has 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 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 lithium vanadium oxide represented by j(Li 2 O) ⁇ kVO x material, where 1 ⁇ x ⁇ 2.5, j>0, k>0, optionally, the lithium vanadium oxide is selected from LiVO 3 , Li 3 V 2 O 5 , Li 4 V 3 O 8 , LiV 3 O 8.
  • LiVO 3 , LiVO 2 , Li 6 V 5 O 15 , LiV 2 O 5 and Li 3 VO 4 is lithium vanadium oxide represented by j(Li 2 O) ⁇ kVO x material, where 1 ⁇ x ⁇ 2.5, j>0, k>0
  • the lithium vanadium oxide is selected from LiVO 3 , Li 3 V 2 O 5 , Li 4 V 3 O 8 , LiV 3 O 8.
  • Li 2 VO 3 , LiVO 2 , Li 6 V 5 O 15 , LiV 2 O 5 and Li 3 VO 4 is Li vanadium oxide represented by
  • Lithium vanadium oxide is generally produced by mixing a lithium source and a vanadium source in a certain stoichiometric ratio.
  • j(Li 2 O) ⁇ kVO x has an obvious discharge platform between 1.5V and 2.0V, and has a high capacity.
  • the first battery cell 61 , the second battery cell 62 and the third battery cell 63 with a suitable second discharge voltage platform can be obtained.
  • the battery pack of the present application with excellent low-temperature performance can be realized.
  • the above-mentioned lithium vanadium oxide can be obtained commercially, or can be prepared by solid phase synthesis, liquid phase synthesis (such as hydrothermal method, microwave method, sol-gel method and liquid phase precipitation) and other methods.
  • 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 88.2% to 100%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 0% to 11.8%.
  • 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 72.6% to 96.1%
  • the discharge capacity corresponding to the second discharge voltage platform accounts for 3.9% to 27.4%.
  • 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 53.1% to 89.6%, and the discharge capacity corresponding to the second discharge voltage platform accounts for 10.4% to 46.9%.
  • 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 to 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 assistant is 275.8-477 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% to 100%, and the mass of the positive electrode functional additive accounts for 0% to 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 89.5% to 96.0%
  • the mass of the positive electrode functional additive accounts for 4.0% to 10.5%.
  • 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 78.5% to 89.5%
  • the mass of the positive electrode functional additive accounts for 10.5% to 21.5%.
  • 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 carbon-coated lithium vanadium oxide.
  • the conductivity of the lithium vanadium oxide can be improved.
  • it helps to improve the energy density and cycle stability of battery cells.
  • a known carbon coating method can be used as a method for carbon coating the lithium vanadium oxide.
  • the following method can be used: adjust the lithium content according to the ratio of each element of the lithium vanadium oxide and the required carbon coating amount.
  • a solvent is added.
  • the solvent can be ethanol, water or acetone.
  • the mixed solution is ball milled, dried, granulated and calcined to obtain carbon-coated lithium vanadium oxide material.
  • the discharge cut-off voltage of the first battery cell is 1.8 to 2.0 V
  • the discharge cut-off voltage of the second battery cell is 1.6 to 1.8 V
  • the The discharge cut-off voltage of the third battery cell is 1.4-1.6V.
  • 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 about 10 ⁇ 30%
  • the second battery cell 62 accounts for approximately 25% to 50%
  • the third battery cell 63 accounts for approximately 30% to 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, the cathode functional assistant Li 3 V 2 O 5 , the superconducting carbon black SP as the conductive agent, and the polymer as the binder Vinylidene fluoride (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, and separated. After strips and cutting into pieces, the positive electrode piece is obtained.
  • NMP N-methylpyrrolidone
  • the positive electrode functional additive has been carbon-coated in advance.
  • the mass ratio of the positive electrode active material, conductive carbon black, and binder PVDF is 96:2:2.
  • the positive electrode functional additive Li 3 V 2 O 5 and the first positive electrode active The mass ratio of substance NCM is 2:98.
  • the negative active material graphite, superconducting carbon black SP as the conductive agent, SBR as the binder, and CMC-Na as the thickener are dispersed and mixed in deionized water as the solvent in a mass ratio of 96:1:1:2 Uniformly, the negative electrode slurry is obtained; the negative electrode slurry is evenly coated on the negative electrode current collector copper foil; after drying, cold pressing, slitting and cutting, the negative electrode sheet is obtained.
  • ethylene carbonate (EC), dimethyl carbonate (DMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent. Then dissolve the fully dried lithium salt LiPF 6 in the mixture. In the final organic solvent, prepare an electrolyte solution with a concentration of 1 mol/L.
  • the above-mentioned positive electrode pieces, isolation films, and negative electrode pieces are stacked in sequence so that the isolation film is between the positive electrode pieces and the negative electrode pieces to play an isolation role, and then the bare cells are obtained by winding them; the bare cells are placed in the outer packaging After drying, electrolyte is injected into the shell, and the first battery cell I-1 is obtained through processes such as vacuum packaging, standing, formation, and shaping.
  • the first battery cell I-2 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 LiVO 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 LiVO 3 .
  • 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 Li 4 V 3 O 8 I-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 Li 4 V 3 O 8 I-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 Li 3 V 2 O 5 were used as the positive electrode active material.
  • LFP lithium iron phosphate
  • Li 3 V 2 O 5 the positive electrode active material
  • 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 Li 3 V 2 O 5 were used as the positive electrode active material.
  • LMO lithium manganate
  • Li 3 V 2 O 5 the positive electrode active material
  • 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 Li 2 VO 3 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 Li 2 VO 3 6.
  • the first battery cell I-7 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 LiVO 2 .
  • 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 LiVO 2 .
  • the first battery cell I-8 was obtained in the same manner as in Preparation Example I-1, except that the first positive electrode active material lithium iron phosphate (LFP) and the positive electrode functional additive Li 2 VO 3 were used as the positive electrode active material.
  • LFP lithium iron phosphate
  • Li 2 VO 3 the positive electrode active material
  • 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 manganate (LMO) and the positive electrode functional additive LiVO 2 were used as the positive electrode active material.
  • LMO lithium manganate
  • LiVO 2 the positive electrode functional additive
  • the first battery cell I-10 was obtained in the same manner as in Preparation Example I-1 except that only LiNi 0.6 Co 0.2 Mn 0.2 O 2 (NCM) was used as 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 lithium iron phosphate (LFP) was used as the positive electrode active material.
  • LFP lithium iron phosphate
  • the first positive active material lithium iron phosphate (LFP) and the positive functional additive Li 3 V 2 O 5 are used, and the mass ratio of the positive functional additive Li 3 V 2 O 5 to the first positive active material LFP is Except for 4:96, the same operation as in Preparation Example I-1 was performed to obtain the first battery cell I-12.
  • the first battery cell I-13 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive Li 3 V 2 O 5 to the first positive electrode active material NCM was 13.5:86.5.
  • 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 Li 3 V 2 O 5 to the first positive electrode active material NCM was 7.5:92.5.
  • 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 LiVO 3 to the first positive electrode active material NCM was 7.5:92.5.
  • 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 Li 4 V 3 O 8 to the first positive electrode active material NCM was 7.5:92.5.
  • 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 Li 3 V 2 O 5 to the first positive electrode active material LFP was 7.5:92.5.
  • 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 Li 3 V 2 O 5 to the first positive electrode active material LMO was 7.5:92.5.
  • 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 Li 2 VO 3 to the first positive electrode active material NCM was 7.5:92.5.
  • the second battery cell II-7 was obtained in the same manner as in Preparation Example I-7, except that the mass ratio of the positive electrode functional additive LiVO 2 to the first positive electrode active material NCM was 7.5:92.5.
  • 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 Li 2 VO 3 to the first positive electrode active material LFP was 7.5:92.5.
  • the second battery cell II-9 was obtained in the same manner as in Preparation Example I-9, except that the mass ratio of the positive electrode functional additive LiVO 2 to the first positive electrode active material LMO was 7.5:92.5.
  • the second battery cell II-10 was obtained in the same manner as Preparation Example I-1 except that the mass ratio of the positive electrode functional additive Li 3 V 2 O 5 to the first positive electrode active material NCM was 4:96.
  • the first positive active material lithium iron phosphate (LFP) and the positive functional additive Li 3 V 2 O 5 are used, and the mass ratio of the positive functional additive Li 3 V 2 O 5 to the first positive active material LFP is Except for 13.5:86.5, the second battery cell II-11 was obtained in the same manner as in Preparation Example I-1.
  • the positive electrode active material uses the first positive electrode active material lithium manganate (LMO) and the positive electrode functional additive LiVO 2 , and the mass ratio of the positive electrode functional additive LiVO 2 to the first positive electrode active material LMO is 13.5:86.5, it is the same as the preparation example I-1 is operated in the same manner to obtain the second battery cell II-12.
  • LMO lithium manganate
  • LiVO 2 the mass ratio of the positive electrode functional additive LiVO 2 to the first positive electrode active material LMO is 13.5:86.5
  • the second battery cell II-13 was obtained in the same manner as Preparation Example I-13 except that the mass ratio of the positive electrode functional additive Li 3 V 2 O 5 to the first positive electrode active material NCM was 20:80.
  • the second battery cell II-14 was obtained in the same manner as in Preparation Example I-10.
  • the second battery cell II-15 was obtained in the same manner as in Preparation Example I-11.
  • the second battery cell II-16 was obtained in the same manner as in Preparation Example I-1.
  • 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 Li 3 V 2 O 5 to the first positive electrode active material NCM was 13.5:86.5.
  • 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 LiVO 3 to the first positive electrode active material NCM was 13.5:86.5.
  • 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 Li 4 V 3 O 8 to the first positive electrode active material NCM was 13.5:86.5.
  • 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 Li 3 V 2 O 5 to the first positive electrode active material LFP was 13.5:86.5.
  • 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 Li 3 V 2 O 5 to the first positive electrode active material LMO was 13.5:86.5.
  • 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 Li 2 VO 3 to the first positive electrode active material NCM was 13.5:86.5.
  • 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 LiVO 2 to the first positive electrode active material NCM was 13.5:86.5.
  • the third battery cell III-8 was obtained in the same manner as Preparation Example I-8 except that the mass ratio of the positive electrode functional additive Li 2 VO 3 to the first positive electrode active material LFP was 13.5:86.5.
  • 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 LiVO 2 to the first positive electrode active material LMO was 13.5:86.5.
  • the third battery cell III-10 was obtained in the same manner as Preparation Example II-10, except that the mass ratio of the positive electrode functional additive Li 3 V 2 O 5 to the first positive electrode active material NCM was 21.5:78.5.
  • the third battery cell III-11 was obtained in the same manner as Preparation Example II-11 except that the mass ratio of the positive electrode functional additive Li 3 V 2 O 5 to the first positive electrode active material LFP was 21.5:78.5.
  • the third battery cell III-12 was obtained in the same manner as Preparation Example II-12, except that the mass ratio of the positive electrode functional additive LiVO 2 to the first positive electrode active material LMO was 21.5:78.5.
  • the third battery cell III-13 was obtained in the same manner as in Preparation Example I-10.
  • the third battery cell III-14 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-15 was obtained in the same manner as in Preparation Example I-1.
  • 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.
  • 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-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-12 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-12. 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-13 to replace the second battery cell II-1, and using the third battery cell III-10 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.
  • 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-10 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-13 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-10 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-14 to replace the second battery cell II-1. Except for the three battery cells III-1, the same operation was performed as in Example 1 to assemble a battery pack.
  • 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.
  • the 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+Li 3 V 2 O 5 4.25 2.0 NCM+LiVO 3 4.25 2.0 NCM+Li 4 V 3 O 8 4.25 2.0 LFP+Li 3 V 2 O 5 3.80 2.0 LMO+Li 3 V 2 O 5 4.25 2.0 NCM+Li 2 VO 3 4.25 2.0 NCM+LiVO 2 4.25 2.0 LFP+Li 2 VO 3 3.80 2.0 LMO+LiVO 2 4.25 2.0
  • 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 73.0% to 78.7%.
  • 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 total energy retention rate at 20°C reaches 70.7% ⁇ 78.0%.
  • Example 1 and Example 13 the mass proportion of the positive electrode functional additive in each of the first battery cell, the second battery cell and the third battery cell and the proportion of the discharge capacity corresponding to the second discharge voltage platform are The ratio is within the preferred range described in this application, and the total energy retention rate of the battery pack at -20°C reaches 76.2% to 78.0%.
  • the mass proportion of the cathode functional additive in each of the first battery cell and the second battery cell, and the proportion of discharge capacity corresponding to the second discharge voltage platform of the first battery cell are here. Outside the preferred range described in the application, the total energy retention rate of the battery pack at -20°C is 74.3%.
  • 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 78.0%.
  • Example 15 the discharge cut-off voltage of the second battery cell and the third battery cell at -20°C was too high, and the total energy retention rate of the battery pack at -20°C was 72.0%.
  • Example 16 the discharge cut-off voltage of the first battery cell and the second battery cell is too low. Although the total energy retention rate of the battery pack at -20°C is 79.0%, the cycle performance of the battery cells will be damaged as mentioned above. .
  • Example 17 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 74.0%.
  • Example 18 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.
  • the discharge cut-off voltage is > the discharge cut-off voltage of the first battery cell, and the total energy retention rate of the battery pack at -20°C is 73.0%.
  • Example 19 the discharge cut-off voltages of the first battery cell, the second battery cell and the third battery cell are all too low at -20°C. Although the total energy retention rate of the battery pack at -20°C reaches 80.0%, As mentioned above, the cycle performance of the battery cells will be impaired.
  • Example 20 the discharge cut-off voltages of the first battery cell, the second battery cell and the third battery cell are all too high at -20°C, and the total energy retention rate of the battery pack at -20°C is 63.0

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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Abstract

本申请提供电池包和用电装置。电池包包括电池包箱体和被收纳在电池包箱体中的电池单体，电池包箱体的内部空间由i 1、i 2、…、i n共n个区域组成，n为大于等于2的正整数，其中第i (m-1)区域中配置有第i (m-1)电池单体，第i m区域中配置有第i m电池单体，第i m电池单体包围第i (m-1)电池单体的周围排布，m依次取值大于1且小于等于n的每一个正整数，第i (m-1)电池单体和第i m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，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i (m-1)电池单体和第i m电池单体各自的正极活性物质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，正极功能助剂为锂钒氧化物，在第i (m-1)电池单体和第i m电池单体各自中，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，第i m电池单体的第二放电电压平台对应的放电容量占比＞第i (m-1)电池单体的第二放电电压平台对应的放电容量占比。

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由i 1、i 2、…、i n共n个区域组成，n为大于等于2的正整数，其中第i (m-1)区域中配置有第i (m-1)电池单体，第i m区域中配置有第i m电池单体，所述第i m电池单体包围所述第i (m-1)电池单体的周围排布，m依次取值大于1且小于等于n的每一个正整数，所述第i (m-1)电池单体和所述第i m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i (m-1)电池单体和所述第i m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锂钒氧化物，在所述第i (m-1)电池单体和所述第i m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i m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i (m-1)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，正极功能助剂为锂钒氧化物，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。
在优选实施方式中，所述电池包包括电池包箱体和被收纳在所述电池包箱体中的电池单体，所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成，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锂钒氧化物，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。
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。
在优选实施方式中，所述正极功能助剂为由j(Li 2O)·kVO x表示的锂钒氧化物，其中1≤x≤2.5，j＞0，k＞0，可选地，所述锂钒氧化物为选自LiVO 3、Li 3V 2O 5、Li 4V 3O 8、LiV 3O 8、Li 2VO 3、LiVO 2、Li 6V 5O 15、LiV 2O 5和Li 3VO 4的一种或多种。
由此，通过选择性能优异的锂钒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。
在优选实施方式中，在所述第i (m-1)电池单体、第i m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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、 第二区域和第三区域组成时，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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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88.2％～100％，所述第二放电电压平台对应的放电容量占0％～11.8％。
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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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72.1％～96.1％，所述第二放电电压平台对应的放电容量占3.9％～27.4％。
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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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53.1％～89.6％，所述第二放电电压平台对应的放电容量占10.4％～46.9％。
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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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。
在优选实施方式中，所述正极功能助剂的理论克容量为275.8～477mAh/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。
在优选实施方式中，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。
在优选实施方式中，当所述第i (m-1)电池单体和第i m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i (m-1)电池单体中所述第一正极活性物质占正极活性物质的质量占比大于所述第i m电池单体中所述第一正极活性物质占正极活性物质的质量占比，所述第i (m-1)电池单体中所述正极功能助剂占正极活性物质的质量占比小于所述第i m电池单体中所述正极功能助剂占正极活性物质的质量占比。
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i m区域中的第i m电池单体的正极功能助剂的质量占比＞配置在第i (m-1)区域中的第i (m-1)电池单体的正极功能助剂的质量占比，能够使第i m电池单体的低温能量保持率＞第i (m-1)电池单体的低温能量保持率＞，能够使第i (m-1)电池单体和第i m电池单体在低温下释放的能量大致一致，即能够使所述电池包中所述n个区域内的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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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。
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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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89.5％～96.0％，所述正极功能助剂的质量占4.0％～10.5％。
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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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78.5％～89.5％，所述正极功能助剂的质量占10.5％～21.5％。
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。
在优选实施方式中，所述正极功能助剂为碳包覆的锂钒氧化物。
由此，通过对作为正极功能助剂的锂钒氧化物进行碳包覆，能够提高作为正极功能助剂的锂钒氧化物的导电性，从而有助于提高电池单体的能量密度和循环稳定性。
在优选实施方式中，在0℃以下的温度下，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，所述第一电池单体的放电截止电压为1.8～2.0V，所述第二电池单体的放电截止电压为1.6～1.8V，所述第三电池单体的放电截止电压为1.4～1.6V。
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。
在优选实施方式中，当所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成时，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是具有双放电电压平台的电池单体的恒流放电曲线图，其中，图中曲线表示本申请一实施方式的电池包内的具有第一放电电压平台和第二放电电压平台的电池单体的恒流放电曲线图。
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，锂钒氧化物具有较低的对锂电位。当锂钒氧化物作为正极功能助剂添加在常规正极活性物质中时，其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。
基于此，本申请提出了以下技术方案和具体实施方式。
本申请提供一种电池包，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由i 1、i 2、…、i n共n个区域组成，n为大于等于2的正整数(例如n为2、3、4、5、6、7、8、9、10、11或12)，其中第i (m-1)区域中配置有第i (m-1)电池单体，第i m区域中配置有第i m电池单体，所述第i m电池单体包围所述第i (m-1)电池单体的周围排布，m依次取值大于1且小于等于n的每一个正整数，所述第i (m-1)电池单体和所述第i m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i (m-1)电池单体和所述第i m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锂钒氧化物，在所述第i (m-1)电池单体和所述第i m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i m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i (m-1)电池单体的所述第二放电电压平台对应的放电容量占比。
电池包
下面，以电池包的内部空间具有三个区域为例(即n＝3)，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锂钒氧化物。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。如图3所示的具有双放电电压平台的电池单体的恒流放电曲线图：该放电曲线有两个放电电压平台，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。
如图3所示，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；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。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，正极功能助剂为锂钒氧化物，该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j(Li 2O)·kVO x表示的锂钒氧化物，其中1≤x≤2.5，j＞0，k＞0，可选地，所述锂钒氧化物为选自LiVO 3、Li 3V 2O 5、Li 4V 3O 8、LiV 3O 8、Li 2VO 3、LiVO 2、Li 6V 5O 15、LiV 2O 5和Li 3VO 4的一种或多种。
锂钒氧化物一般是由锂源和钒源按一定化学计量比混合后制得，j(Li 2O)·kVO x在1.5V～2.0V之间具有明显的放电平台，且容量较高。
由此，通过选择性能优异的锂钒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。
上述的锂钒氧化物可通过市购获得，或者利用固相合成法、液相合成法(例如水热法、微波法、溶胶-凝胶法和液相沉淀)等方法制备。
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88.2％～100％，所述第二放电电压平台对应的放电容量占0％～11.8％。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72.6％～96.1％，所述第二放电电压平台对应的放电容量占3.9％～27.4％。
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53.1％～89.6％，所述第二放电电压平台对应的放电容量占10.4％～46.9％。
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275.8～477mAh/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89.5％～96.0％，所述正极功能助剂的质量占4.0％～10.5％。
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78.5％～89.5％，所述正极功能助剂的质量占10.5％～21.5％。
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锂钒氧化物。
由此，通过对作为正极功能助剂的锂钒氧化物进行碳包覆，能够 提高锂钒氧化物的导电性。从而，有助于提高电池单体的能量密度和循环稳定性。
作为对锂钒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：按照锂钒氧化物各元素配比与所需的碳包覆量，调整锂钒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，即可得到碳包覆的锂钒氧化物材料。通过对锂钒氧化物进行碳包覆，能够提升锂钒氧化物的电导率。
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1.8～2.0V，所述第二电池单体的放电截止电压为1.6～1.8V，所述第三电池单体的放电截止电压为1.4～1.6V。
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Li 3V 2O 5、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Li 3V 2O 5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LiVO 3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Li 4V 3O 8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Li 3V 2O 5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Li 3V 2O 5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Li 2VO 3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LiVO 2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磷酸铁锂(LFP)和正极功能助剂Li 2VO 3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锰酸锂(LMO)和正极功能助剂LiVO 2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]
除了正极活性物质仅使用LiNi 0.6Co 0.2Mn 0.2O 2(NCM)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磷酸铁锂(LFP)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Li 3V 2O 5，且正极功能助剂Li 3V 2O 5与第一正极活性物质LFP的质量比为4:96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]
除了正极功能助剂Li 3V 2O 5与第一正极活性物质NCM的质量比为13.5:86.5以外，与制备例I-1同样地操作，获得第一电池单体I-13。
II.第二电池单体的制备
[制备例II-1]
除了正极功能助剂Li 3V 2O 5与第一正极活性物质NCM的质量比为7.5:92.5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LiVO 3与第一正极活性物质NCM的质量比为7.5:92.5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Li 4V 3O 8与第一正极活性物质NCM的质量比为7.5:92.5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Li 3V 2O 5与第一正极活性物质LFP的质量比为7.5:92.5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Li 3V 2O 5与第一正极活性物质LMO的质量比为7.5:92.5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Li 2VO 3与第一正极活性物质NCM的质量比为7.5:92.5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LiVO 2与第一正极活性物质NCM的质量比为7.5:92.5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Li 2VO 3与第一正极活性物质LFP的质量比为7.5:92.5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LiVO 2与第一正极活性物质LMO的质量比为7.5:92.5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Li 3V 2O 5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-10。
[制备例II-11]
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Li 3V 2O 5，且正极功能助剂Li 3V 2O 5与第一正极活性物质LFP的质量比为13.5:86.5以外，与制备例I-1同样地操作，获得第二电池单体II-11。
[制备例II-12]
除了正极活性物质使用第一正极活性物质锰酸锂(LMO)和正极功能助剂LiVO 2，且正极功能助剂LiVO 2与第一正极活性物质LMO的质量比为13.5:86.5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]
除了正极功能助剂Li 3V 2O 5与第一正极活性物质NCM的质量比为20:80以外，与制备例I-13同样地操作，获得第二电池单体II-13。
[制备例II-14]
与制备例I-10同样地操作，获得第二电池单体II-14。
[制备例II-15]
与制备例I-11同样地操作，获得第二电池单体II-15。
[制备例II-16]
与制备例I-1同样地操作，获得第二电池单体II-16。
III.第三电池单体的制备
[制备例III-1]
除了正极功能助剂Li 3V 2O 5与第一正极活性物质NCM的质量比为13.5:86.5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LiVO 3与第一正极活性物质NCM的质量比为13.5:86.5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Li 4V 3O 8与第一正极活性物质NCM的质量比为13.5:86.5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Li 3V 2O 5与第一正极活性物质LFP的质量比为13.5:86.5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Li 3V 2O 5与第一正极活性物质LMO的质量比为13.5:86.5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Li 2VO 3与第一正极活性物质NCM的质量比为13.5:86.5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LiVO 2与第一正极活性物质NCM的质量比为13.5:86.5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Li 2VO 3与第一正极活性物质LFP的质量比为13.5:86.5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LiVO 2与第一正极活性物质LMO的质量比为13.5:86.5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Li 3V 2O 5与第一正极活性物质NCM的质量比为21.5:78.5以外，与制备例II-10同样地操作，获得第三电池单体III-10。
[制备例III-11]
除了正极功能助剂Li 3V 2O 5与第一正极活性物质LFP的质量比为21.5:78.5以外，与制备例II-11同样地操作，获得第三电池单体III-11。
[制备例III-12]
除了正极功能助剂LiVO 2与第一正极活性物质LMO的质量比为21.5:78.5以外，与制备例II-12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-10同样地操作，获得第三电池单体III-13。
[制备例III-14]
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-14。
[制备例III-15]
与制备例I-1同样地操作，获得第三电池单体III-15。
(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-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-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。
[实施例13]
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-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。
[实施例14]
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-13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15]
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。
[实施例20]
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-10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-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2]
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-15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。
[对比例3]
除了使用第二电池单体II-16代替第二电池单体II-1，使用第三电池单体III-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。
[对比例4]
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。
(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1～20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中的放电曲线中，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+Li 3V 2O 5 4.25 2.0
NCM+LiVO 3 4.25 2.0
NCM+Li 4V 3O 8 4.25 2.0
LFP+Li 3V 2O 5 3.80 2.0
LMO+Li 3V 2O 5 4.25 2.0
NCM+Li 2VO 3 4.25 2.0
NCM+LiVO 2 4.25 2.0
LFP+Li 2VO 3 3.80 2.0
LMO+LiVO 2 4.25 2.0
2、电池包-20℃总能量保持率的测定
另外，对实施例1～20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1～20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 PCTCN2022105501-appb-000001
根据上述表2的结果可知，在实施例1～9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73.0％～78.7％。
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66.7％。
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67.4％。
Figure PCTCN2022105501-appb-000002
根据上述表3的结果可知，在实施例1、10～13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，电池包-20℃总能量保持率达到70.7％～78.0％。并且，实施例1和实施例13中，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76.2％～78.0％。
而在实施例14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、和第一电池单体的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74.3％。
Figure PCTCN2022105501-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78.0％。
而在实施例15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72.0％。
在实施例16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79.0％，但是如上所述会损害电池单体的循环性能。
在实施例17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74.0％。
在实施例18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73.0％。
在实施例19中，-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过低，虽然电池包-20℃总能量保持率达到80.0％，但是如上所述会损害电池单体的循环性能。
在实施例20中，-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过高，电池包-20℃总能量保持率为63.0
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 (18)

  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由i 1、i 2、…、i n共n个区域组成，n为大于等于2的正整数，其中第i (m-1)区域中配置有第i (m-1)电池单体，第i m区域中配置有第i m电池单体，所述第i m电池单体包围所述第i (m-1)电池单体的周围排布，m依次取值大于1且小于等于n的每一个正整数，其中，
    所述第i (m-1)电池单体和所述第i m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i (m-1)电池单体和所述第i m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锂钒氧化物，
    在所述第i (m-1)电池单体和所述第i m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i m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i (m-1)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，
    所述电池包箱体的内部空间由第一区域、第二区域和第三区域组成，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锂钒氧化物，
    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。
  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j(Li 2O)·kVO x表示的锂钒氧化物，其中1≤x≤2.5，j＞0，k＞0，可选地，所述锂钒氧化物为选自LiVO 3、Li 3V 2O 5、Li 4V 3O 8、LiV 3O 8、Li 2VO 3、LiVO 2、Li 6V 5O 15、LiV 2O 5和Li 3VO 4的一种或多种。
  4. 根据权利要求2～3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。
  5. 根据权利要求2～4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88.2％～100％，所述第二放电电压平台对应的放电容量占0％～11.8％。
  6. 根据权利要求2～5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72.1％～96.1％，所述第二放电电压平台对应的放电容量占3.9％～27.4％。
  7. 根据权利要求2～6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53.1％～89.6％，所述第二放电电压平台对应的放电容量占10.4％～46.9％。
  8. 根据权利要求2～7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。
  9. 根据权利要求2～8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275.8～477mAh/g。
  10. 根据权利要求2～9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。
  11. 根据权利要求2～10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。
  12. 根据权利要求2～11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％。
  13. 根据权利要求2～12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89.5％～96.0％，所述正极功能助剂的质量占4.0％～10.5％。
  14. 根据权利要求2～13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78.5％～89.5％，所述正极功能助剂的质量占10.5％～21.5％。
  15. 根据权利要求2～14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锂钒氧化物。
  16. 根据权利要求2～15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1.8～2.0V，所述第二电池单体的放电截止电压为1.6～1.8V，所述第三电池单体的放电截止电压为1.4～1.6V。
  17. 根据权利要求2～16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)。
  18. 一种用电装置，其特征在于，包括权利要求1～17中任一项所述的电池包。
PCT/CN2022/105501 2022-07-13 2022-07-13 电池包和用电装置 WO2024011454A1 (zh)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101714629A (zh) * 2009-11-10 2010-05-26 苏州大学 锂离子电池用三平台混合正极材料及其制备方法
WO2012132525A1 (ja) * 2011-03-25 2012-10-04 三洋電機株式会社 パック電池
CN103700817A (zh) * 2013-12-18 2014-04-02 江苏科捷锂电池有限公司 LiV3O8 和LiNi0.4Co0.2Mn0.4O2共混改性锂电池正极材料的制备方法
CN105161756A (zh) * 2015-09-28 2015-12-16 广西师范大学 一种具有电量耗尽预警功能的磷酸铁锂锂离子电池
CN107004920A (zh) * 2014-12-26 2017-08-01 三洋电机株式会社 电池组

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101714629A (zh) * 2009-11-10 2010-05-26 苏州大学 锂离子电池用三平台混合正极材料及其制备方法
WO2012132525A1 (ja) * 2011-03-25 2012-10-04 三洋電機株式会社 パック電池
CN103700817A (zh) * 2013-12-18 2014-04-02 江苏科捷锂电池有限公司 LiV3O8 和LiNi0.4Co0.2Mn0.4O2共混改性锂电池正极材料的制备方法
CN107004920A (zh) * 2014-12-26 2017-08-01 三洋电机株式会社 电池组
CN105161756A (zh) * 2015-09-28 2015-12-16 广西师范大学 一种具有电量耗尽预警功能的磷酸铁锂锂离子电池

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