Battery packs and power consuming devices

Abstract

The present application relates to a battery pack and a power consumption device, the battery pack including a battery case and a first battery cell and a second battery cell disposed in the battery case, the first battery cell has a higher heat dissipation capacity than the second battery cell, and the amount of lithium replenisher W1 in the first battery cell is greater than the amount of lithium replenisher W2 in the second battery cell, W1>0 and W2>0.

Description

[Technical field]

[0001] This application relates to the field of batteries, and more particularly to battery packs and power consuming devices. [Background technology]

[0002] Lithium-ion batteries and other secondary batteries lose a certain amount of capacity during use, which leads to a reduction in their service life. Lithium-ion batteries and other secondary batteries are significantly affected by temperature during use, and especially under low-temperature operating conditions, the available capacity of the battery cells drops significantly and the low-temperature output characteristics deteriorate rapidly.

[0003] Furthermore, within a battery pack, as the number of secondary batteries in the battery pack increases, the volume and electrical quantity of the battery pack increase, the difference in temperature rise between the inside of the battery pack and the external area near the edges becomes even larger, and the capacity difference between the battery cells becomes significant, making it impossible to guarantee balance in battery capacity, resulting in problems such as poor performance of the entire battery pack. Summary of the Invention

[0004] In view of the above problems, the present application provides a battery pack and a power consuming device that can improve the capacity balance between battery cells and improve overall performance.

[0005] According to a first aspect, the present application provides a battery pack including a battery case and a first battery cell and a second battery cell disposed in the battery case; The heat dissipation capacity at the location of the first battery cell is higher than the heat dissipation capacity at the location of the second battery cell, and the amount of lithium replenisher W1 added in the first battery cell is greater than the amount of lithium replenisher W2 added in the second battery cell, where W1>0 and W2≧0.

[0006] According to a second aspect, the present application further provides a battery pack including a battery case and a first battery cell and a second battery cell disposed in the battery case; Due to the difference in heat dissipation in the battery case, the temperature of the first battery cell is lower than the temperature of the second battery cell, and the amount of lithium replenisher W1 added in the first battery cell is greater than the amount of lithium replenisher W2 added in the second battery cell, where W1>0 and W2≧0.

[0007] Compared with the prior art, the present application includes at least the following beneficial effects:

[0008] In the present application, a first battery cell and a second battery cell having different lithium replenisher contents are arranged in separate regions in a battery pack, and the lithium replenisher is used to compensate for the lithium loss, and different lithium replenisher contents are used to achieve different lithium replenishment effects, and different lithium replenisher contents are installed separately for the battery cells to accommodate the difference in capacity loss between the battery cells caused by the temperature difference depending on the placement position, specifically, the battery cell installed above the position with high heat dissipation capacity has a higher lithium replenisher content, and conversely, the battery cell installed above the position with low heat dissipation capacity has a relatively low lithium replenisher content, thereby achieving the function of differentially replenishing the lithium loss of the battery cells and improving the capacity balance between the battery cells.

[0009] On the premise that the above battery pack does not implement balancing intervention of the BMS system and does not use the assistance of extra assemblies such as a self-heating device, the lithium replenisher is activated, and the capacity self-balancing effect is achieved as much as possible through the cell design of the battery cells, so that the discharge capacity of each battery cell in the battery pack at room temperature or low temperature maintains good consistency, thereby improving the characteristics of the entire battery pack.

[0010] In any embodiment of the present application, the first battery cell and the second battery cell are formed by adding different contents of lithium replenisher to battery cells of the same chemical system and capacity.

[0011] In any embodiment of the present application, the lithium supplement is added into the positive electrode active material layer of the battery cell, and the added amount is the mass content of the lithium supplement in the corresponding positive electrode active material layer. By controlling the added amount of the lithium supplement in the positive electrode active material layer of the battery cell, the capacity of the battery cell can be easily and flexibly adjusted.

[0012] In any embodiment of the present application, the amount of lithium replenisher added in the first battery cell and the second battery cell is both less than or equal to 25%.

[0013] In any embodiment of the present application, a difference in discharge capacity caused by a difference in heat dissipation due to the location of the second battery cell and the first battery cell is ΔC, a difference in recovery capacity of the positive electrode active material caused by a difference in the amount of lithium replenisher added to the first battery cell and the second battery cell is ΔD, and a difference in normal discharge capacity caused by a difference in the amount of lithium replenisher added to the first battery cell and the second battery cell is ΔE, ΔC, ΔD, and ΔE are, The condition ΔC=ΔD+ΔE is satisfied. In this way, the sum of the difference in recovery capacity of the positive electrode active material caused by the difference in the added lithium replenisher and the difference in normal discharge capacity exactly compensates for the difference in discharge capacity caused by the different positions of the battery pack. This achieves capacity balance between the battery cells.

[0014] In any embodiment of the present application, a temperature difference caused by a difference in heat dissipation between the second battery cell and the first battery cell is ΔT, and a difference in the amount of lithium replenisher added between the first battery cell and the second battery cell is ΔW, then ΔW=W1-W2, and ΔT and ΔW are When 0<ΔT≦5℃, 0<ΔW≦6%. When 5<ΔT≦10℃, the condition 6%<ΔW≦15% is met.

[0015] In any embodiment of the present application, When 0<ΔT≦5℃, 2%≦ΔW≦4%. When 5<ΔT≦10℃, 6%≦ΔW≦12%.

[0016] In any embodiment of the present application, the lithium replenisher has the formula Li 1+x M y A z and M is selected from at least one of Ni, Co, Mn, Mo, Ru, Fe, and Ti; A is selected from at least one of O, F, S, P and Cl.

[0017] In any embodiment of the present application, 0 <x≦5、0.10<y<2、2≦z≦4である。

[0018] In any embodiment of the present application, the initial coulombic efficiency of the lithium supplement is set to e, where e satisfies the condition that 0.2≦e≦0.95.

[0019] In any embodiment of the present application, in the battery case, the first battery cell is located outside the second battery cell; Or, a heat exchange area between the first battery cell and the battery case is larger than a heat exchange area between the second battery cell and the battery case.

[0020] According to a third aspect, the present application provides a power consumption device including a battery pack according to any of the above embodiments for supplying electrical energy thereto.

[0021] The above description is only an outline of the technical solution of the present application. In order to more clearly understand the technical solution of the present application, the following provides specific embodiments of the present application, which can be implemented in accordance with the contents of the specification, and in order to more clearly understand the above and other objectives, features and advantages of the present application. [Brief description of the drawings]

[0022] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments. The drawings are for the purpose of illustrating the preferred embodiments and should not be considered as limiting the present application. In the drawings, the same elements use the same reference numerals. The drawings are as follows:

[0023] [Figure 1] FIG. 1 is a schematic diagram of a battery pack according to an embodiment of the present application. [Diagram 2] FIG. 1 is a schematic diagram showing the arrangement of battery cells in a battery pack according to a conventional embodiment. [Diagram 3] 2 is a schematic diagram showing an arrangement of one embodiment of battery cells in the battery pack shown in FIG. 1. [Figure 4] 1. FIG. 4 is a schematic diagram showing an arrangement of battery cells in the battery pack shown in FIG. 1 according to another embodiment. [Diagram 5] 1. FIG. 4 is a schematic diagram showing an arrangement of battery cells in the battery pack shown in FIG. 1 according to another embodiment. [Figure 6] 1 is a schematic diagram of a power consuming device that uses a battery pack as a power source in accordance with an embodiment of the present application. [Explanation of symbols]

[0024] 10 Battery pack 11 First battery cell 12 Second battery cell 13 3rd battery cell 14 4th battery cell DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The following describes in detail the embodiments of the technical solution of the present application with reference to the drawings. The following embodiments are only used to more clearly explain the technical solution of the present application, and are merely examples, which do not limit the scope of protection of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. The terms used herein are merely for the purpose of describing specific examples and are not intended to limit the present application. The terms "including" and "having" and their equivalents in the specification and claims of this application and the description of the drawings above are intended to be non-exclusive.

[0027] In the description of the embodiments of the present application, the terms "first", "second", etc. are merely intended to distinguish different objects, and should not be understood as indicating or implying the relative importance, or the quantity, specific order, or hierarchical relationship of the technical features shown. In the description of the embodiments of the present application, unless otherwise clearly limited, "plurality" means two or more.

[0028] Reference to an "embodiment" in this specification means that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment of the present application. The appearances of the term "embodiment" in various places in this specification do not necessarily refer to the same embodiment, nor do they refer to embodiments that are mutually exclusive, independent, or alternative to other embodiments. Those skilled in the art will understand, both explicitly and implicitly, that the embodiments described in this specification can be combined with other embodiments.

[0029] The term "and / or" in the description of the embodiments of the present application merely describes the relationship between related objects and indicates that three types of relationships can exist, for example, A and / or B can indicate three situations: A exists alone, A and B exist simultaneously, and B exists alone. In this specification, the symbol " / " generally indicates that the related objects before and after it are in an "or" relationship.

[0030] In describing the embodiments of the present application, the term "plurality" refers to two or more (including two); similarly, "multiple sets" refers to two or more sets (including two sets); and "multiple sheets" refers to two or more sheets (including two sheets).

[0031] In describing the embodiments of the present application, the orientations or positional relationships indicated by terms such as "center," "longitudinal," "lateral," "length," "width," "thickness," "up," "down," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are based on the orientations or positional relationships shown in the drawings and are intended to make the embodiments of the present application easier to explain and simplify the description, and do not indicate or imply that the subject devices or elements have a specific orientation or should be configured and operated in a specific orientation, and therefore should not be understood as limiting the embodiments of the present application.

[0032] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, the terms "attached," "connected," "connected," "fixed," and the like should be understood in a broad sense, for example, they may be fixedly connected, detachably connected, or integral. They may be mechanically connected or electrically connected. They may be directly connected, indirectly connected via an intermediate medium, or may be communication within two elements or an interaction relationship between two parts. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of the present application according to the specific circumstances.

[0033] FIG 1 illustrates an example battery pack 10. Referring to FIG 1 and FIG 2, the battery pack 10 may include a battery case (not shown) and a plurality of battery cells disposed within the battery case. The battery case includes an upper housing and a lower housing, and the upper housing may be placed over the lower housing to form a sealed space for accommodating the plurality of battery cells. The plurality of battery cells may be arranged within the battery case in any manner.

[0034] Generally, as shown in FIG. 2, one battery cell is installed at each position 1 of the battery pack without considering differences in position or differences in battery cells. Furthermore, the battery cells installed at each position 1 are generally the same battery cells. Note that "the same battery cells" here refers to cells of the same chemical system and the same battery capacity. Here, the same chemical system mainly refers to the battery cells being made of the same material, and further, the battery cells may have the same external size, for example, battery cells of the same model number from the same manufacturer.

[0035] The present technical personnel have found that the capacity loss during the use of lithium-ion batteries is mainly due to the loss of active lithium and polarization, which leads to a reduction in the service life. Secondary batteries such as lithium-ion batteries are greatly affected by temperature during use, and especially under low-temperature operating conditions, the available capacity of the battery cells is greatly reduced and the low-temperature output characteristics are rapidly deteriorated. Therefore, on the one hand, the operating temperature of the battery cells is increased to reduce the significant reduction in the available capacity of the battery cells, and on the other hand, the temperature difference caused by the arrangement position of each battery cell is reduced, thereby avoiding the problem of the poor characteristics of the entire battery pack due to the imbalance in capacity between each battery cell.

[0036] Therefore, in general, the methods for maintaining the capacity balance of battery cells mainly include the following several methods:

[0037] The first is to use a BMS system (also called battery babysitter or battery manager) to perform balancing, but active cell balancing places high requirements on the design and placement of the BMS, and passive cell balancing wastes some cell capacity.

[0038] The second method involves disposing a self-heating device in the battery pack to increase the overall temperature of the battery pack and improve the battery characteristics, but this increases costs, occupies internal space, and does not achieve self-balance.

[0039] Third, by arranging cells of different chemical types, batteries with higher low-temperature resistance can be placed in areas with faster heat dissipation capabilities, ensuring a capacity balance between the battery cells.

[0040] Referring to FIG. 3, a battery pack 10 according to an embodiment of the present application includes a battery case and a first battery cell 11 and a second battery cell 12 installed in the battery case.

[0041] The heat dissipation capacity of the first battery cell 11 at location 1 is higher than the heat dissipation capacity of the second battery cell 12 at location 2, and the amount of lithium replenisher W1 added in the first battery cell 11 is greater than the amount of lithium replenisher W2 added in the second battery cell 12, where W1>0 and W2≧0.

[0042] The temperature of the first battery cell 11 is lower than that of the second battery cell 12, and the capacity of the first battery cell 11 is lower. Therefore, in order to improve the discharge capacity of the battery and ensure the consistency of the overall characteristics of the battery pack, it is necessary to further improve the capacity of the first battery cell 11. Therefore, activating more lithium replenisher in the first battery cell 11 can, on the one hand, significantly alleviate the thermodynamic capacity loss caused by lithium loss by activating more lithium replenisher in the first battery cell 11, thereby compensating for the capacity loss caused by temperature difference polarization; on the other hand, since the impedance of the lithium replenisher itself is larger than that of the main positive electrode material, adding more lithium replenisher during the charging and discharging process generates more heat, which increases the temperature and alleviates the capacity loss caused by low-temperature polarization.

[0043] In the present application, a first battery cell and a second battery cell having different lithium replenisher contents are arranged in separate regions in a battery pack, and the lithium replenisher is used to compensate for the lithium loss, and different lithium replenisher contents are used to achieve different lithium replenishment effects, and different lithium replenisher contents are installed separately for the battery cells to accommodate the difference in capacity loss between the battery cells caused by the temperature difference depending on the placement position, specifically, the battery cell installed above the position with high heat dissipation capacity has a higher lithium replenisher content, and conversely, the battery cell installed above the position with low heat dissipation capacity has a relatively low lithium replenisher content, thereby achieving the function of differentially replenishing the lithium loss of the battery cells and improving the capacity balance between the battery cells.

[0044] On the premise that the above battery pack does not implement balancing intervention of the BMS system and does not use the assistance of extra assemblies such as a self-heating device, the lithium replenisher is activated, and the capacity self-balancing effect is achieved as much as possible through the cell design of the battery cells, so that the discharge capacity of each battery cell in the battery pack at room temperature or low temperature maintains good consistency, thereby improving the characteristics of the entire battery pack.

[0045] The present invention relates to a method for improving the capacity of secondary batteries, such as lithium ion batteries in a battery pack, by supplementing the positive electrode with lithium to compensate for the loss of lithium, and the method is simple in operation and low in cost.

[0046] 3, in a battery case, position 1 is close to the edge of the battery case, and position 2 is inside position 1. Therefore, since position 1 is close to the edge of the battery case, the maximum amount of heat exchange that can be performed between position 1 and the external environment of the battery case is obviously larger than the maximum amount of heat exchange that can be performed between position 2 and the external environment of the battery case. Therefore, position 1 has a higher heat dissipation capacity than position 2, and position 2 has a lower heat dissipation capacity than position 1.

[0047] Furthermore, in the battery pack 10, the maximum amount of heat exchange Q1 that can take place between the location 1 of the first battery cell 11 and the external environment of the battery case is greater than the maximum amount of heat exchange Q2 that can take place between the location 2 of the second battery cell 12 and the external environment of the battery case, and the amount of lithium replenisher W1 added to the first battery cell 11 is greater than the amount of lithium replenisher W2 added to the second battery cell 12, with W1>0 and W2≧0.

[0048] In some embodiments, the first battery cell 11 and the second battery cell 12 are all battery cells of the same chemical type. Furthermore, each battery cell in the battery case is all battery cells of the same chemical type.

[0049] Specifically, the cell battery may be a lithium nickel cobalt manganese oxide ternary battery, a lithium nickel cobalt aluminate ternary battery, a lithium iron phosphate battery, a lithium manganese iron phosphate battery, a lithium manganate battery, a lithium nickel manganate battery, a lithium titanate battery, or a lithium cobalt oxide battery in a lithium ion battery, or a Prussian blue battery, a Prussian white battery, a metal oxide battery, or a phosphate battery in a sodium ion battery, or other secondary battery cells. Preferably, all the battery cells in the battery case are of the same chemical system, for example, all are lithium nickel cobalt manganate ternary batteries in a lithium ion battery.

[0050] In some embodiments, each battery cell, such as the first battery cell 11 and the second battery cell 12, may be formed by adding different contents of lithium replenisher to battery cells of the same chemistry and capacity.

[0051] In some embodiments, the lithium supplement is added into the positive electrode active material layer of the battery cell, and the added amount is the mass content of the lithium supplement in the corresponding positive electrode active material layer. By controlling the added amount of the lithium supplement in the positive electrode active material layer of the battery cell, the capacity of the battery cell can be easily and flexibly adjusted.

[0052] In some embodiments, the amount of lithium replenisher added in each battery cell, such as the first battery cell and the second battery cell, is 25% or less, such as 2%, 3%, 5%, 8%, 10%, 12%, 15%, 18%, 20%, 23%, 25%, etc. Furthermore, the amount of lithium replenisher added in each battery cell, such as the first battery cell and the second battery cell, is 2% to 15%, or 5% to 10%.

[0053] In some embodiments, the difference in discharge capacity caused by the difference in heat dissipation due to the location of the second battery cell and the first battery cell is ΔC, the difference in recovery capacity of the positive electrode active material caused by the difference in the amount of lithium replenisher added to the first battery cell and the second battery cell is ΔD, and the difference in normal discharge capacity caused by the difference in the amount of lithium replenisher added to the first battery cell and the second battery cell is ΔE, ΔC, ΔD, and ΔE are The condition ΔC=ΔD+ΔE is satisfied.

[0054] In the above formula, the left side of the equation is the difference in discharge capacity due to different positions of the battery pack, and the right side of the equation is the sum of the difference in recovery capacity of the positive electrode active material caused by the difference in the amount of lithium supplement added and the difference in normal discharge capacity. The equation is established, and the sum of the difference in recovery capacity of the positive electrode active material caused by the difference in the amount of lithium supplement added and the difference in normal discharge capacity exactly compensates for the difference in discharge capacity due to the different positions of the battery pack, thereby achieving capacity balance between the battery cells.

[0055] Specifically, if the discharge capacities affected by heat dissipation due to the locations of the first and second battery cells are C1 and C2, respectively, then ΔC=C2-C1. If the recovery capacities of the positive electrode active material due to the amount of lithium replenisher added to the first and second battery cells are D1 and D2, respectively, then ΔD=D1-D2. If the normal discharge capacities due to the amount of lithium replenisher added to the first and second battery cells are E1 and E2, respectively, then ΔE=E1-E2. In this case, C2-C1=D1-D2+E1-E2.

[0056] Furthermore, the recovery capacities of the positive electrode active material brought about by lithium replenishment by the lithium replenisher per unit mass of the first battery cell and the second battery cell are d1 and d2, respectively, and when W1 and W2 are added to the first battery cell and the second battery cell, respectively, D1 = W1d1 and D2 = W2d2.

[0057] Furthermore, the normal discharge capacities provided by lithium replenishment of the first battery cell and the second battery cell with a unit mass of lithium replenisher are e1 and e2, respectively, and when W1 and W2 are added to the first battery cell and the second battery cell, respectively, E1=W1e1 and E2=W2e2.

[0058] Furthermore, C2-C1=W1d1-W2d2±W1e1-W2e2.

[0059] If we extrapolate from this to the N-class cells, C i -C i-1 =W i D i -W i-1 D i-1 +W i E i -W i-1 E i-1 It is.

[0060] Note that the difference in discharge capacity caused by the difference in heat dissipation between the second battery cell and the first battery cell due to their locations is ΔC, which is actually the temperature difference between the second battery cell and the first battery cell themselves due to the difference in heat dissipation, that is, the temperature difference ΔT caused by the difference in heat dissipation between the second battery cell and the first battery cell, and the temperature difference causes the difference in discharge capacity. In other words, the left side of the above equation, ΔC, is a parameter related to ΔT. In battery cells of the same chemical system, d1, d2, e1, and e2 may be considered to be invariant, and therefore the right side of the above equation is a parameter related to W1 and W2.

[0061] Therefore, referring to specific examples and the experience and research of the technicians of the present application, in some embodiments, taking the temperature difference due to the heat dissipation difference between the second battery cell and the first battery cell as ΔT, and the difference in the addition amount of the lithium supplement of the first battery cell and the second battery cell as ΔW, then ΔW = W1 - W2, and ΔT and ΔW satisfy the following conditions.

[0062] When 0 < ΔT ≤ 5°C, 0 < ΔW ≤ 6%, preferably, 2% ≤ ΔW ≤ 4%.

[0063] When 5 < ΔT ≤ 10°C, 6% < ΔW ≤ 15%, preferably, 6% ≤ ΔW ≤ 12%.

[0064] In some embodiments, the chemical formula of the lithium supplement is Li 1+x M y A z where M is selected from at least one of the transition metal elements Ni, Co, Mn, Mo, Fe, Ru, and Ti, A is selected from at least one of the non-metal elements O, F, S, and Cl.

[0065] It should be noted that the values taken by x, y, and z may be any values as long as they can make the valence of the above compound zero. In some embodiments, 0 < x ≤ 5, 0.10 < y < 2, 2 ≤ z ≤ 4. Preferably, 0 < x ≤ 4, 0.1 ≤ x ≤ 0.5, and more preferably 0.1 ≤ x ≤ 0.3. Preferably, 0.55 ≤ y ≤ 0.90, and more preferably 0.65 ≤ y ≤ 0.85. Preferably, 3.5 ≤ z ≤ 4 or z = 2.

[0066] Furthermore, the lithium supplement is Li 1.47 Mn 1.6 O 3.7 F 0.3 , Li 2 Mn 2 O 4 , Li 1.16 Ni 0.22 Mn 0.6 O 2 , Li 1.13 Ni 0.07 Co0.14 Mn 0.58 O 2 , Li 2 Ni 0.1 Cu 0.9 O 2 , Li 2 Ni 0.4 Cu 0.55 Mg 0.05 O 2 , Li 6 Chief of Staff 4 , Li 6 NiO 4 , Li 6 MnO 4 , Li 6 FeO 4 , Li 5 FeO 4 may include, but is not limited to, at least one of:

[0067] In some embodiments, the initial coulombic efficiency of the lithium supplement is set as e, where e satisfies the condition that 0.2≦e≦0.95.

[0068] The time for activating the lithium replenisher is specified as follows: on the basis of introducing lithium-rich lithium replenisher, it can be activated in the first cycle, or it can be activated and added in divided time sections and voltage gradients during the cycle process of the battery, so as to realize accurate lithium replenishment, while improving the battery characteristics and reducing the loss of energy density; the first cycle charging voltage can be selected as different potentials from 3.75 to 5V according to the type of lithium replenisher.

[0069] In some embodiments, when the state of health of the battery cell is equal to or lower than a preset threshold, the lithium replenisher is activated to replenish the lithium of the battery cell. The state of health of the battery cell is obtained in the following manner: when the battery cell is at a preset charging node, the state of health of the battery cell is obtained.

[0070] The preset charging node may be any one of at least two charging nodes set based on experimental data such as the cycle life or capacity loss status of the battery cell. Specifically, the preset charging node may be a time node or a cycle number node where the loss of active lithium is large, which is predicted based on the experimental data.

[0071] The SOH indicates the remaining battery life of the battery cell at the present time and has a meaning known in the art. Specifically, the SOH may be defined based on the cycling life or the capacity fade.

[0072] The above-mentioned preset threshold is a preset SOH value for evaluating the degree of loss of active lithium in the battery cell. If the SOH is equal to or less than the preset threshold, the battery cell may be deemed to be in a state in which active lithium needs to be replenished, in which case the lithium replenishment material may be activated to replenish the lithium in the battery cell. There may be multiple means for activating the lithium replenishment material, for example, the lithium replenishment material may be activated by increasing the charging voltage or charging rate, increasing the temperature, etc., or the activation of the lithium replenishment material is realized by charging and discharging at a certain voltage or rate. Furthermore, the charging voltage may be 3.75 to 5V.

[0073] In a situation where the initial temperature of the entire battery case is the same and the battery case is placed in the same external environment, as heat exchange between the battery case and the external environment progresses, a temperature difference gradually occurs inside the battery case depending on the placement position due to the difference in heat dissipation capacity at different positions in the battery case (or the difference in the maximum amount of heat exchange that can be performed between the battery case and the external environment). For example, in the example shown in FIG. 3, a temperature difference may occur in which the temperature at position 2 is higher than the temperature at position 1. Since the capacity of a battery cell decreases significantly under low temperature operating conditions, when the battery pack is in a low temperature operating condition, the temperature at position 1 is obviously lower than the temperature at position 2, and if the battery cells placed at positions 1 and 2 are the same battery cells, the capacity of the battery cell placed at position 1 is obviously lower than the capacity of the battery cell placed at position 2 because the temperature is obviously lower.

[0074] This application considers this factor in advance and compensates for the difference by intentionally adding lithium replenisher. Therefore, by installing the first battery cell 11 at position 1 and the second battery cell 12 at position 2, and making the amount of lithium replenisher W1 added in the first battery cell 11 greater than the amount of lithium replenisher W2 added in the second battery cell 12, the capacity of each battery cell can tolerate a certain range of temperature difference changes, thereby achieving capacity self-balance.

[0075] In the present application, when only the effect of the difference in position on the heat dissipation capacity is considered, the heat dissipation capacity of the outer position close to the edge of the battery case is superior to that of the inner position farther from the edge. For example, as shown in FIG 4, position 1 is an outer position closer to the edge than position 2, and the heat dissipation capacity of position 1 is superior to that of position 2, and position 2 is an outer position closer to the edge than position 3, and the heat dissipation capacity of position 3 is superior to that of position 2.

[0076] Furthermore, in the example shown in Figure 4, if the first battery cell 11 is installed at position 1, the second battery cell 12 is installed at position 2, and the third battery cell 13 is installed at position 3, and the amounts of lithium replenisher added to the first battery cell 11, the second battery cell 12, and the third battery cell 13 are W1, W2, and W3, respectively, then W1>W2>W3, W1>0, W2>0, and W3≧0.

[0077] In this application, when only the effect of the difference in position on the heat dissipation capacity is considered, for the outermost positions of the outermost battery cells, the battery cell closest to the battery case can exchange heat more directly with the battery case than the battery cells arranged inside. There is also a difference in the heat exchange area between the battery cells arranged at different outermost positions and the battery case. The heat dissipation capacity of the positions with a large heat exchange area with the battery case is superior to the positions with a small heat exchange area with the battery case.

[0078] For example, as shown in FIG. 5, as described above, positions 1 to 3 are outer positions closer to the edge than position 4, and the heat dissipation capacity of positions 1 to 3 is superior to that of position 4. In positions 1 to 3, position 1 is at a corner position of the battery case compared to positions 2 to 3, and positions 2 to 3 are at positions that are not corners of the side wall of the battery case. The heat exchange area between position 1 and the battery case is larger than the heat exchange area between positions 2 to 3 and the battery case. Therefore, position 1 has a greater heat dissipation capacity than positions 2 to 3.

[0079] Furthermore, in the example shown in Figure 5, the first battery cell 11 is installed at position 1, the second battery cell 12 is installed at position 2, the third battery cell 13 is installed at position 3, and the fourth battery cell 14 is installed at position 4, and if the amounts of lithium replenisher added to the first battery cell 11, the second battery cell 12, the third battery cell 13 and the fourth battery cell 14 are W1, W2, W3 and W4, respectively, W1>W2>W4, W1>W3>W4, W1>0, W2>0, W4≧0.

[0080] W1 and W2 may be set to the same or different values ​​according to the actual situation.

[0081] In summary, when the heat dissipation capability of the location of the first battery cell is greater than that of the location of the second battery cell, there may be some arrangement methods, including but not limited to the following:

[0082] In arrangement method 1, the first battery cell is positioned outside the second battery cell within the battery case.

[0083] In the second arrangement, the heat exchange area between the first battery cell and the battery case is larger than the heat exchange area between the second battery cell and the battery case inside the battery case.

[0084] Any of the above arrangement methods can achieve that the heat dissipation capability at the location of the first battery cell is greater than the heat dissipation capability at the location of the second battery cell.

[0085] Furthermore, in some examples, as shown in Fig. 5, the battery cells arranged at the outermost positions 1-2 in the battery case are configured to be in direct contact with the inside of the battery case. At this time, the heat exchange area between the battery cells and the battery case is mainly determined by the contact area between the battery cells and the battery case. That is, when the contact area between a first battery cell and the battery case is larger than the contact area between a second battery cell and the battery case in the battery case, the heat dissipation capacity at the position where the first battery cell is located is larger than the heat dissipation capacity at the position where the second battery cell is located.

[0086] The present application further provides a power consuming device including at least one of the battery packs of the present application. The battery pack may be used as a power source for the power consuming device or as an energy storage element for the power consuming device. The power consuming device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, energy storage systems, etc.

[0087] As the power consuming device, a battery pack can be selected according to its usage requirements.

[0088] 6 shows an example of a power consumption device, such as a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. To meet the high power and high energy density requirements for the secondary battery of the power consumption device, a battery pack or a battery module can be used.

[0089] Other examples of the device may be a mobile phone, a tablet computer, a notebook computer, etc. Such devices are generally required to be lightweight and thin, and can use a secondary battery as a power source.

[0090] The examples described below are illustrative and are only for the purpose of explaining the present application, and should not be understood as limiting the present application. If no specific techniques or conditions are shown in the examples, they are carried out according to the techniques or conditions described in the literature in this field, or according to the product instructions. If no manufacturer is listed for the reagents or equipment used, they are all commercially available general products.

[0091] Exam Information and Instructions 1) Battery cell capacity C test: The initial discharge capacity of a battery cell is defined as the capacity discharged at 0.33C from the upper cut-off voltage of each battery cell to the lower cut-off voltage of each battery cell at the standard test temperature (-20℃ / 0℃).

[0092] 2) Test of the recovered discharge capacity d after lithium replenishment with a unit mass of lithium replenisher: It is not considered that the lithium replenisher itself releases capacity, but only that the lithium replenisher is used to recover the capacity loss caused by the loss of lithium ions in the positive electrode active material. In this case, d = (Cap - Cap 0 / W) and Cap 0 is the discharge capacity of the battery before lithium replenishment, Cap is the discharge capacity of the battery after lithium replenishment, and W is the mass content of the lithium replenisher in the positive electrode active material layer. Cap, Cap 0 may be obtained using the battery cell capacity C test described above.

[0093] 3) Capacity retention rate of the battery cell: The battery cell is fully charged and placed in an incubator for 2 hours, then discharged at a rate of 0.33C to the lower cut-off voltage of the battery cell, and the capacity is recorded to obtain the capacity retention rate of the battery cell.

[0094] Comparative Example 1 In the battery pack of Comparative Example 1, the same battery cells (same chemical system, same capacity, same material and size) are arranged at all positions in the battery case. As shown in FIG. 3, the battery cell at position 1 (the area closest to the battery case) is designated as the first battery cell 11, and the battery cell at position 2 (located in the center of the area at the end of the battery case) is designated as the second battery cell 12. At this time, the environmental temperature of the battery case is -20°C. In other words, each battery cell is the same, the cell capacity is the same, and no lithium supplement is added to the positive electrode active material layer. However, since the first battery cell and the second battery cell are located at different positions in the battery case, there is a temperature difference between the first battery cell and the second battery cell due to the difference in heat dissipation, and the temperature difference causes a difference in battery cell capacity, 0°C<ΔT≦5°C. Specifically, as shown in Table 1.

[0095] The timing of measuring the temperature of the battery cell before refilling with lithium and the capacity of the battery cell before refilling with lithium are the same or do not differ significantly. Specifically, the temperature of the battery cell before refilling with lithium is obtained by attaching a temperature sensing wire to the middle position of the outer case of the cell, and the temperature acquisition time is detected when the battery case in which each battery cell is placed is placed at the corresponding environmental temperature for 120 minutes, at which time it is considered that a thermal equilibrium state has been reached.

[0096] Specifically, the positive electrode active material layers of the first battery cell and the second battery cell in Comparative Example 1 were both NCM523-based.

[0097] Comparative Example 2 The battery pack of Comparative Example 2 is basically the same as that of Comparative Example 1, with the only difference being that the material and size of the battery case are slightly different, and the temperature difference between the first battery cell and the second battery cell before lithium replenishment is 5°C<ΔT≦10°C.

[0098] Example 1 The battery pack of Example 1 is basically the same as that of Comparative Example 1, and the only difference is that, based on Comparative Example 1, lithium replenishers W1 and W2 were added to the positive electrode active material layers of the first and second battery cells, respectively.

[0099] Specifically, the chemical formula for lithium supplements is Li 1.47 Mn 1.6 O 3.7 F 0.3 (The initial coulombic efficiency is defined as the ratio of the initial discharge capacity to the initial charge capacity of a unit mass of lithium replenisher.) In other words, in Example 1, the first battery cell and the second battery cell to which the lithium replenisher W1 and W2 were added were used to replace the first battery cell and the second battery cell in Comparative Example 1, respectively.

[0100] The test flow of the coulombic efficiency of the lithium replenisher is H2 / H1*100%. Here, the discharge specific capacity H1 of the lithium replenisher is the capacity of a unit mass of additive charged at 0.33C from the lower cut-off voltage of the lithium replenisher to the upper cut-off voltage of each battery cell at the standard test temperature (-20℃ / 0℃) within the lithium replenisher voltage range. The discharge specific capacity H2 of the lithium replenisher is the capacity of a unit mass of additive discharged at 0.33C from the upper cut-off voltage of the lithium replenisher to the lower cut-off voltage of each battery cell at the standard test temperature (-20℃ / 0℃) within the lithium replenisher voltage range. The same applies below.

[0101] Example 2 The battery pack of Example 2 is basically the same as that of Comparative Example 2, with the difference being that, based on Comparative Example 2, lithium replenishers W1 and W2 were added to the positive electrode active material layers of the first and second battery cells, respectively.

[0102] The test results for the available capacity of the entire battery pack at 25°C for Comparative Examples 1-2 and Examples 1-2, the temperature of the battery cell before replenishment with lithium, the capacity of the battery cell before replenishment with lithium, the available capacity of the entire battery pack before replenishment with lithium, the amount of lithium replenisher W in each battery cell (the mass content of the lithium replenisher in the positive electrode active material layer), the capacity of the battery cell after replenishment with lithium, the available capacity of the entire battery pack after replenishment with lithium, and the improvement rate of the capacity retention rate of the battery pack are as shown in Table 1.

[0103] Here, the available capacity of the entire battery pack is the smaller of the actual capacities of the first and second battery cells in the battery pack, in other words, the minimum capacity of each battery cell in the battery pack. For example, the available capacity of the entire battery pack before lithium refueling is the smaller of the actual capacities of the first and second battery cells before lithium refueling. The available capacity of the entire battery pack after lithium refueling is the smaller of the actual capacities of the first and second battery cells after lithium refueling.

[0104] The available capacity (Ah) of the entire battery pack at 25° C. is the available capacity of the corresponding battery pack at 25° C. before lithium replenishment, and therefore each comparative example and example in Table 1 are the same.

[0105] The usable capacity maintenance rate of the entire battery pack before lithium replenishment is the ratio of the usable capacity of the entire battery pack under a low environmental temperature to the usable capacity of the entire battery pack at 25°C.

[0106] The usable capacity maintenance rate of the entire battery pack after lithium replenishment is the ratio of the usable capacity of the entire battery pack at a low environmental temperature after lithium replenishment to the usable capacity of the entire battery pack at 25°C.

[0107] In the table, after adding the lithium replenisher, the first cycle charging voltage is activated at 4.4V.

[0108] The lithium replenishment SOH (preset threshold) is used to define the time to activate the lithium replenisher, and the lithium replenishment SOH (preset threshold) is defined based on the capacity loss, specifically, it is the preset value of the usable capacity maintenance rate of the whole battery pack in the table. For example, in Table 1, the lithium replenishment SOH (preset threshold) is 70%, which indicates that when the current usable capacity maintenance rate of the whole battery pack before lithium replenishment reaches 70%, each battery cell in the battery pack is activated. The current usable capacity maintenance rate of the whole battery pack is the ratio of the current usable capacity of the whole battery pack to the usable capacity of the whole battery pack at 25°C.

[0109] The increase in the battery pack capacity maintenance rate is the usable capacity maintenance rate of the entire battery pack after lithium replenishment minus the usable capacity maintenance rate of the entire battery pack before lithium replenishment.

[0110] The above parameters have the same or similar meanings in Table 2.

[0111] [Table 1]

[0112] Comparative Examples 3 to 4 The battery pack of Comparative Example 3 is basically the same as Comparative Example 1, and the same battery cells (same chemical system, same capacity, same material and size) are arranged at all positions within each battery case. The differences are that the battery cells of Comparative Example 3 are different from those of Comparative Example 1, and the environmental temperature of the battery cases is different, specifically 0°C.

[0113] Comparative Example 4 The battery pack of Comparative Example 4 is basically the same as that of Comparative Example 3, with the only difference being that the material and size of the battery case are slightly different, and the temperature difference between the first battery cell and the second battery cell before lithium replenishment is 5°C<ΔT≦10°C.

[0114] Example 3 The battery pack of Example 3 is basically the same as that of Comparative Example 3, except that, based on Comparative Example 3, lithium replenishers W1 and W2 are added to the positive electrode active material layers of the first and second battery cells, respectively. Specifically, the chemical formula of the lithium replenisher is L i1.47 Mn 1.6 O 3.7 F 0.3 and the initial coulombic efficiency e is 60% (the definition of the initial coulombic efficiency is the ratio of the initial discharge capacity to the initial charge capacity of a unit mass of lithium replenisher).

[0115] Example 4 The battery pack of Example 4 is basically the same as that of Comparative Example 4, with the difference being that, based on Comparative Example 4, lithium replenishers W1 and W2 were added to the positive electrode active material layers of the first and second battery cells, respectively.

[0116] The test results for the available capacity of the entire battery pack at 25°C for Comparative Examples 3 to 4 and Examples 3 to 4, the temperature of the battery cell before replenishment with lithium, the capacity of the battery cell before replenishment with lithium, the available capacity of the entire battery pack before replenishment with lithium, the amount of lithium replenisher W in each battery cell (the mass content of the lithium replenisher in the positive electrode active material layer), the capacity of the battery cell after replenishment with lithium, the available capacity of the entire battery pack after replenishment with lithium, and the improvement rate of the capacity retention rate of the battery pack are as shown in Table 2.

[0117] [Table 2]

[0118] The final point to be explained is as follows: The above embodiments are merely for illustrating the technical solutions of the present application, and are not intended to limit the same. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand the following: It is still possible to modify the technical solutions described in the above embodiments, or to substitute some or all of the technical features therein with equivalents, and these modifications or substitutions do not cause the substance of the corresponding technical solutions to depart from the scope of the technical solutions of the embodiments of the present application, and all of them should be included in the scope of the claims and the specification of the present application. In particular, the technical features mentioned in each embodiment can be combined in any manner as long as there is no structural contradiction. The present application is not limited to the specific embodiments disclosed in this specification, and includes all technical solutions included in the claims.

Claims

1. The battery includes a battery case and a first battery cell and a second battery cell disposed in the battery case, A battery pack, characterized in that a heat dissipation capacity at the position of the first battery cell is higher than a heat dissipation capacity at the position of the second battery cell, an amount W1 of lithium replenisher added in the first battery cell is greater than an amount W2 of lithium replenisher added in the second battery cell, and W1>0 and W2>0.

2. The battery includes a battery case and a first battery cell and a second battery cell disposed in the battery case, a temperature of the first battery cell is lower than a temperature of the second battery cell due to a difference in heat dissipation in the battery case, an amount W1 of lithium replenisher added in the first battery cell is greater than an amount W2 of lithium replenisher added in the second battery cell, and W1>0 and W2>0.

3. 3. The battery pack according to claim 1, wherein the first battery cell and the second battery cell are formed by adding lithium replenisher with different contents to battery cells having the same chemical system and capacity.

4. 4. The battery pack according to claim 3, wherein the lithium replenisher is added into the positive electrode active material layer of the battery cell, and the added amount is the mass content of the lithium replenisher in the corresponding positive electrode active material layer.

5. 5. The battery pack according to claim 4, wherein the amount of lithium replenisher added in each of the first battery cell and the second battery cell is 25% or less.

6. If a difference in discharge capacity caused by a difference in heat dissipation or a temperature difference due to the location of the second battery cell and the first battery cell is ΔC, a difference in recovery capacity of the positive electrode active material caused by a difference in the amount of lithium replenisher added to the first battery cell and the second battery cell is ΔD, and a difference in normal discharge capacity caused by a difference in the amount of lithium replenisher added to the first battery cell and the second battery cell is ΔE, then ΔC, ΔD, and ΔE are, The battery pack according to any one of claims 1 to 5, wherein the condition ΔC=ΔD+ΔE is satisfied.

7. If a temperature difference caused by a difference in heat dissipation between the second battery cell and the first battery cell is ΔT, and a difference in the amount of lithium replenisher added between the first battery cell and the second battery cell is ΔW, then ΔW=W1-W2, and ΔT and ΔW are expressed as follows: When 0<ΔT≦5° C., 0<ΔW≦6%; 6. The battery pack according to claim 1, wherein when 5<ΔT≦10° C., the condition 0.06<ΔW≦15% is satisfied.

8. When 0<ΔT≦5° C., 2%≦ΔW≦4%; 8. The battery pack according to claim 7, wherein, when 5<[Delta]T<10[deg.] C., 6%<[Delta]W<12%.

9. The chemical formula of the lithium replenisher is Li １＋ｘ M ｙ A ｚ and M is selected from at least one of Ni, Co, Mn, Fe, Mg, Mo, Ru, and Ti; The battery pack according to any one of claims 1 to 8, wherein A is selected from at least one of O, F, S and Cl.

10. 10. The battery pack according to claim 9, wherein 0<x≦5, 0.10<y<2, and 2≦z≦4.

11. The battery pack according to any one of claims 1 to 10, wherein the initial coulombic efficiency of the lithium replenisher is set to e, where e satisfies the condition 0.2≦e≦0.

9.

12. In the battery case, the first battery cell is located outside the second battery cell; Alternatively, the battery pack according to any one of claims 1 to 11, characterized in that a heat exchange area between the first battery cell and the battery case is larger than a heat exchange area between the second battery cell and the battery case.

13. A power consuming device, characterized in that it comprises a battery pack according to any one of claims 1 to 12, used for supplying electrical energy.

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