Battery pack and electric device

Abstract

The application discloses a battery pack and an electric device. The battery pack comprises a plurality of batteries, at least one partition plate arranged between adjacent batteries, and a battery comprising a shell and an electrode assembly. The shell has a receiving cavity, and the electrode assembly is arranged in the receiving cavity. The receiving cavity has a bottom wall. The partition plate comprises a plate body and a buffer part arranged on both sides of the plate body, and the buffer part abuts against the shell. The battery pack satisfies 85%<=M SOC <=(1+L / W)*100%, and M SOC =D / W. The battery pack can improve the performance of the battery pack by setting the ratio of the maximum thickness of the electrode assembly to the width of the bottom wall, the width of the bottom wall, and the thickness of the buffer part of the partition plate of the battery when the state of charge is 0-100% in advance according to different material systems.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lithium batteries, and particularly relates to a battery pack and a power utilization device. BACKGROUND

[0002] The power battery generally comprises a plurality of single batteries, and adjacent single batteries are mainly separated by a separator to improve the reliability of the power battery, but the existing separator arrangement mode reduces the performance of the power battery. SUMMARY

[0003] The application provides a battery pack to improve the problem of reduced performance of the battery pack, and another object of the application is to provide a power utilization device comprising the battery pack.

[0004] Technical scheme, the battery pack of the application comprises:

[0005] a plurality of batteries;

[0006] at least one separator arranged between adjacent batteries;

[0007] The battery comprises a shell and an electrode assembly; the shell has a receiving cavity, the electrode assembly is arranged in the receiving cavity, the receiving cavity has a bottom wall, the separator comprises a plate body and a buffer portion arranged on both sides of the plate body, and the buffer portion abuts against the shell;

[0008] wherein the battery pack satisfies:

[0009] 85%≤M SOC ≤(1+L / W)×100%, and M SOC =D / W;

[0010] In the formula, the ratio of the maximum thickness of the electrode assembly of the battery to the width of the bottom wall when the state of charge is 0-100% is M SOC , the thickness of the buffer portion is L mm, the width of the bottom wall is W mm, and the maximum thickness of the electrode assembly of the battery when the state of charge is 0-100% is D mm.

[0011] In some embodiments, the battery pack further satisfies:

[0012] 85%≤M SOC ≤106.5%.

[0013] In some embodiments, the battery pack further satisfies:

[0014] 85%≤M (SOC＝0) ; and / or,

[0015] M (SOC＝100％) ≤(1+L / W)×100%;

[0016] In the formula, the ratio of the maximum thickness of the electrode assembly of the battery when the state of charge is 0 to the width of the bottom wall is M (SOC＝0) ;

[0017] The ratio of the maximum thickness of the electrode assembly of the battery when the state of charge is 100% to the width of the bottom wall is M (SOC＝100％) .

[0018] In some embodiments, the battery pack further satisfies:

[0019] 85%≤M (SOC＝0) <100%, 94%≤M (SOC＝100％) ≤(1+L / W)×100%, and M (SOC＝0) <M (SOC＝100％) ;

[0020] In the formula, M (SOC＝0) represents the ratio of the maximum thickness of the electrode assembly of the battery when the state of charge is 0 to the width of the bottom wall;

[0021] M (SOC＝100％) represents the ratio of the maximum thickness of the electrode assembly of the battery when the state of charge is 100% to the width of the bottom wall.

[0022] In some embodiments, the battery pack further satisfies: M (SOC＝0) :M (SOC＝100％) =1:1.05~1.10.

[0023] In some embodiments, the expression of M (SOC＝0) is: M (SOC＝0) =D0 / W; and / or,

[0024] The expression of M (SOC＝100％) is: M (SOC＝100％) =D 100 / W;

[0025] In the formula, the maximum thickness of the electrode assembly of the battery when the state of charge is 0 is D0 mm;

[0026] The maximum thickness of the electrode assembly of the battery when the state of charge is 100% is D 100 mm.

[0027] In some embodiments, D0 satisfies: 17≤D0≤70; and / or,

[0028] D 100 satisfies: 18.8≤D 100 ≤74.6.

[0029] In some embodiments, the thickness L of the buffer portion and the width W of the bottom wall further satisfy:

[0030] 0 < L / W < 6.5%.

[0031] In some embodiments, the thickness L of the buffer portion satisfies: 0 < L < 3; and / or,

[0032] The width W of the bottom wall satisfies: 20 < W < 70.

[0033] In some embodiments, the thickness of the plate body is L1 mm, and satisfies: 0.5 < L / L1 < 2; or, satisfies: 0.65 < L / L1 < 1.5.

[0034] In some embodiments, the buffer portion is in a ring structure, and the width K of the buffer portion is 4 mm to 20 mm.

[0035] In some embodiments, the application further provides a power consumption device comprising the battery pack.

[0036] Advantages: Compared with the prior art, the battery pack of the application comprises a plurality of batteries; at least one partition plate is arranged between adjacent batteries; the battery comprises a shell and an electrode assembly; the shell has a receiving cavity, and the electrode assembly is arranged in the receiving cavity; the receiving cavity has a bottom wall, and the partition plate comprises a plate body and a buffer portion arranged on both sides of the plate body, and the buffer portion abuts against the shell; wherein the battery pack satisfies: 85% < M SOC < (1 + L / W) x 100%, and M SOC = D / W; in the formula, the ratio of the maximum thickness of the electrode assembly of the battery at a state of charge of 0-100% to the width of the bottom wall is M SOC , the thickness of the buffer portion is L mm, the width of the bottom wall is W mm, and the maximum thickness of the electrode assembly of the battery at a state of charge of 0-100% is D mm. By setting the ratio of the maximum thickness of the electrode assembly of the battery at a state of charge of 0-100% to the width of the bottom wall, the ratio of the width of the bottom wall, and the thickness of the buffer portion of the partition plate, the performance of the battery pack can be effectively improved.

[0037] It can be understood that, compared with the prior art, the power consumption device provided in the embodiments of the application has all the technical features and advantages of the battery pack described above, and will not be described here. BRIEF DESCRIPTION OF DRAWINGS

[0038] The technical solutions and other advantages of the application will be apparent from the following detailed description of specific embodiments of the application, with reference to the accompanying drawings.

[0039] Figure 1 The battery pack structure provided in the embodiments of the application is shown in the figure;

[0040] Figure 2 The battery structure provided in the embodiments of the application is shown in the figure;

[0041] Figure 3 A cross-sectional view of a separator according to an embodiment of the present application is provided.

[0042] Figure 4 A cross-sectional view of a separator according to an embodiment of the present application is provided. Figure 3 An enlarged view of A in FIG. 1;

[0043] Figure 5 A cross-sectional view of a housing according to an embodiment of the present application is provided.

[0044] Reference numerals, 1 - battery, 2 - separator, 11 - housing, 12 - electrode assembly, 13 - accommodation cavity, 14 - bottom wall, 21 - plate body, 22 - buffer portion, 121 - jelly-roll. DETAILED DESCRIPTION

[0045] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0046] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "connected", "connected" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or integrally connected; it can be mechanically connected, or electrically connected or can communicate with each other; it can be directly connected, or indirectly connected through an intermediate medium, or the internal communication of two elements or the interaction relationship between two elements. For a person of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. In the description of the present application, the meaning of "multiple" is two or more than two, unless otherwise explicitly specified and limited. In addition, the terms "first", "second" are for the purpose of description only, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include one or more features.

[0047] The following disclosure provides many different embodiments or examples for implementing different structures of the present application. In order to simplify the disclosure of the present application, the components and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application.

[0048] Reference is made to Figures 1 to 5As shown, a battery pack is provided, comprising a plurality of batteries 1 and at least one separator 2, the plurality of batteries 1 are arranged in sequence, and the separator 2 is arranged between adjacent batteries 1, the battery 1 comprises a shell 11 and an electrode assembly 12 arranged in the shell 11; the shell 11 has a receiving cavity 13, and the electrode assembly 12 is arranged in the receiving cavity 13, and the receiving cavity 13 has a bottom wall 14, and the separator 2 comprises a plate body 21 and a buffer portion 22 arranged on both sides of the plate body 21, and the buffer portion 22 abuts against the shell 11;

[0049] Wherein, the battery pack satisfies:

[0050] 85%≤M≤(1+L / W)×100%, and M SOC =D / W;

[0051] In the formula, the ratio of the maximum thickness of the electrode assembly 12 of the battery 1 at a state of charge of 0-100% to the internal thickness of the shell 11 is M SOC , the thickness of the buffer portion 22 is L mm, the internal thickness of the shell 11 is W mm, and the maximum thickness of the electrode assembly 12 of the battery 1 at a state of charge of 0-100% is D mm.

[0052] In some embodiments, the state of charge (SOC) is the ratio of the remaining capacity of the battery after being used for a period of time or long-term storage to the capacity of its fully charged state, commonly expressed in percentage, and the value range is 0-100%, when the state of charge SOC=0, it indicates that the battery is completely discharged, and when the state of charge SOC=100%, it indicates that the battery is fully charged.

[0053] In some embodiments, the battery pack further satisfies: 85%≤M SOC ≤106.5%. The calculation of M SOC may be the ratio of the total length of various substances in the electrode assembly 12 to the width of the bottom wall 14 of the shell 11 of the battery, and M SOC may represent the difficulty of the electrode assembly 12 into the shell, the pressure of the electrode assembly 12 after charging expansion on the shell 11 of the battery, etc. Since the expansion degree of the electrode assembly 12 is different at different states of charge, the size of M SOC directly affects the performance of the secondary battery, and if the M SOC of the lithium ion battery is too large, the pressure of the electrode assembly on the battery shell after expansion will increase, which is easy to cause excessive extrusion of the separator 2 to cause irreversible damage to the battery, directly affecting the safety performance of the lithium ion battery; if the M SOC of the lithium ion battery is smaller, the electrode assembly 12 is easier to enter the shell, but the energy density of the lithium ion battery with small M SOC is also relatively low, which cannot meet the actual use requirements of the battery. Therefore, the influence of M SOC on the performance of the electrode assembly 12 is studied, especially the MSOC The influence of the thickness of the buffer part on the performance of the electrode assembly 12 will effectively improve the overall performance of the battery.

[0054] In some embodiments, referring to Figure 2 and Figure 5 , it should be noted that, regardless of the state of charge of the battery 1, M SOC , the width W of the bottom wall 14 of the shell 11 is always fixed, i.e., the value of W does not change with the expansion of the shell 11; but because the electrode assembly 12 expands to different degrees at different states of charge, and the electrode assembly 12 can also expand locally, the value of D is the maximum thickness at the corresponding state of charge, and D can be obtained by directly measuring the maximum thickness of the electrode assembly at the corresponding state of charge. The specific test method is as follows: charge the battery at a current of 1 / 3C to the upper limit of voltage, and then charge at a constant voltage of 0.05C. Then disassemble the battery, take out the electrode assembly 12, and measure its thickness with a vernier caliper.

[0055] In some embodiments, because the battery is in different charging and discharging states, the size of M SOC , it is necessary to further consider the range of M SOC at the two extreme cases of full charge and full discharge. Therefore, the battery pack provided in the present application further satisfies: 85%≤M (SOC＝0) ; M (SOC＝100％) ≤(1+L / W)×100%; in the formula, M (SOC＝0) represents the ratio of the thickness of the electrode assembly 12 to the width of the bottom wall 14 of the battery 1 when the state of charge is 0; and M (SOC＝100％) represents the ratio of the thickness of the electrode assembly 12 to the width of the bottom wall 14 of the battery 1 when the state of charge is 100%.

[0056] In some embodiments, the battery pack further satisfies: 85%≤M (SOC＝0) <100%, 94%≤M (SOC＝100％) ≤(1+L / W)×100%, and M (SOC＝0) <M (SOC＝100％) .

[0057] In such a design, the jellyroll 121 will be restrained to some extent, thereby obtaining a better shaping effect, and at the same time, the battery will not be deformed due to excessive expansion, so the performance of the jellyroll 121, especially the cycle performance, is greatly improved. Taking a battery system with graphite as the negative electrode as an example, if the state of charge SOC=0, the battery M (SOC＝0)less than 85%, the winding core 121 lacks a binding force throughout the charging and discharging process, and the graphite falls off from the electrode sheet in repeated expansion and contraction, which causes the performance of the battery to decrease; however, if M (SOC＝100％) greater than (1+L / W) x 100%, at this time, the thickness of the winding core 121 not only exceeds the internal thickness of the shell 11, but also directly contacts the separator 2, the center of the large surface of the battery 1 is most severely expanded, the center of the large surface is subjected to the greatest expansion force after the winding core 121 directly contacts the separator 2, the electrolyte is squeezed out from the center of the large surface to form a poor electrolyte area, which is prone to cause lithium precipitation, and ultimately leads to the performance of the battery to decrease. Therefore, only when 85%≤M SOC ≤(1+L / W) x 100% is satisfied, or further 85%≤M (SOC＝0) <100% and 94%≤M (SOC＝100％) ≤(1+L / W) x 100% is satisfied, at this time, the winding core 121 is subjected to a certain binding force, and the large surface is not poor in liquid due to excessive expansion force, thereby causing the performance of the battery to decrease; by setting the ratio of the maximum thickness of the electrode assembly to the internal thickness of the shell, the internal thickness of the shell, and the thickness of the buffer portion of the separator of the battery at the state of charge of 0-100% in advance, the expansion of the battery and the gap between the separators are effectively controlled within a certain proportion, the limitation of the boundary size of the battery is ensured, and the interface problems caused by the gas production of the battery, the shrinkage of the electrode material during charging and discharging, and the like are effectively avoided, thereby improving and improving the performance of the battery.

[0058] In some embodiments, M (SOC＝0) is expressed as: M (SOC＝0) =D0 / W; M (SOC＝100％) is expressed as: M (SOC＝100％) =D 100 / W; wherein the maximum thickness of the electrode assembly 12 of the battery 1 at the state of charge of 0 is D0 mm, and the maximum thickness of the electrode assembly 12 of the battery 1 at the state of charge of 100 is D 100 mm.

[0059] In some embodiments: D0 satisfies: 17 mm≤D0≤70 mm; D 100 satisfies: 18.8 mm≤D 100 ≤74.6 mm. Preferably, D0 satisfies: 27.2 mm≤D0≤50 mm; D 100 satisfies: 28.2 mm≤D 100 ≤53.2 mm; further preferably, D0 satisfies: 32 mm≤D0≤50 mm; D 100 satisfies: 35.7 mm≤D 100 ≤53.2 mm. It is worth noting that D0 and D100 When all the above ranges are satisfied, the boundary size of the battery can be further determined, and new problems generated in the processes of winding core assembly, battery packaging assembly and battery transportation can be avoided.

[0060] In some embodiments, referring to Figure 3 and Figure 4 , the thickness L of the buffer portion 22 and the width W of the bottom wall 14 further satisfy: 0 < L / W ≤ 6.5%. The thickness L of the buffer portion 22 refers to the dimension of the buffer portion 22 of the separator 2 protruding relative to the plate body 21; wherein the thickness L of the buffer portion 22 satisfies: 0 mm < L ≤ 3 mm; the width W of the bottom wall 14 satisfies: 20 mm ≤ W ≤ 70 mm. When 0 < L / W ≤ 6.5% is satisfied, sufficient expansion space can be provided for the winding core by setting the buffer portion on the separator, so as to improve the cycle performance of the battery. Further, when 0 < L / W ≤ 6.5% is satisfied, M (SOC＝0) is any value or a range value between any two values of 85%, 86%, 87%, 88%, 89%, 90%, 92%, 94%, 96%, 98%, M (SOC＝100％) is any value or a range value between any two values of 94%, 96%, 98%, 100%, 102%, 104%, 106%, all of which are within the protection scope of the present application.

[0061] In some embodiments, the separator 2 all has the buffer portion 22, the buffer portion 22 is a back-shaped frame structure, the buffer portion 22 is arranged along the four peripheral edges of the separator 2, and the buffer portion 22 is symmetrically arranged along the two sides of the separator 2; wherein the back-shaped frame is composed of a hard material, so that the buffer portion 22 is difficult to be compressed.

[0062] In some embodiments, the thickness L of the buffer portion 22 can be any value or a range value between any two values of 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm and 3.0 mm; the width W of the bottom wall 14 can be any value or a range value between any two values of 20 mm, 30 mm, 40 mm, 50 mm, 60 mm, 70 mm. Preferably, the thickness L of the buffer portion 22 satisfies: 1 mm ≤ L ≤ 2 mm; the width of the bottom wall 14 satisfies: 40 mm ≤ W ≤ 50 mm.

[0063] In some embodiments, referring to Figure 4 , the thickness of the plate body 21 is L1 mm, which satisfies: 0.5 ≤ L / L1 ≤ 2; further preferably, 0.65 ≤ L / L1 ≤ 1.5. When 0.5 ≤ L / L1 ≤ 2 is satisfied, the separator 2 will neither affect the arrangement of the electrode assembly 12 because the thickness of the plate body 21 is too large, nor affect its use strength because the thickness of the plate body 21 is too small.

[0064] In some embodiments, referring toFigure 4 The buffer 22 is in a ring shape, and the width K of the buffer 22 is 4mm-20mm. When the width K satisfies the above range, the effect of the abutment of the buffer 22 can be further ensured. Preferably, the width K can be any one of 4mm, 5mm, 6mm, 7mm, 8mm, 9mm, 10mm, 12mm, 14mm, 16mm, 18mm, 20mm or a range between any two values.

[0065] In some embodiments, the application provides a power consuming device, and the power consuming device of the application comprises the secondary battery described above. The power consuming device can be used for, but is not limited to, a backup power supply, an electric motor, an electric vehicle, an electric motorcycle, an assisted bicycle, a bicycle, an electric tool, a household large storage battery, etc.

[0066] Different battery packs of Examples 1-7 were prepared respectively, and the width W of the bottom wall 14, the thickness L of the buffer 22, and the maximum thickness of the electrode assembly when the charge state is 0 and 100% respectively were determined, and the results are recorded in Table 1. The cycle performance of the battery packs of Examples 1-7 was tested after assembly, and the specific test results are shown in Table 2. The value of D is based on the state of the battery pack when the charge state is 0, and the width W of the bottom wall 14, the thickness L of the buffer 22, and the maximum thickness of the electrode assembly when the charge state is 0 and 100% can be directly obtained by measurement.

[0067] Taking the dimensions of Example 1 as an example, M SOC The batteries with less than 85% and more than (1+L / W)×100% were prepared as Comparative Examples 1 and 2 respectively, and a battery without the buffer 22 was prepared as Comparative Example 3.

[0068] In Table 2, the cycle performance refers to the capacity retention rate after 2000 cycles of constant current charge and discharge at 25℃ and at a rate of 1C.

[0069] The test method of the cycle performance is as follows: the separator is pasted on the opposite two large faces of the battery shell with double-sided tape, then the battery with the pasted separator is placed in a clamp, the clamp clamps the separators on both sides of the battery shell, and a pre-tightening force of 200kgf is applied, then the capacity retention rate after 2000 cycles of constant current charge and discharge at 25℃ and at a rate of 1C. The large face is the face with the largest area of the shell.

[0070] Table 1

[0071] D mm W mm L mm L / W % [CD AT D0 mm] D 100 mm]] Example 1 44 50 0.2 0.4％ 44 47.5 Example 2 45 50 0.5 1％ 45 48.6 Example 3 49 50 3 6％ 49 52.9 Example 4 30.4 33.3 0.4 1.2％ 30.4 32.6 Example 5 21 23 0.2 0.8％ 21 22.9 Example 6 72 80 4 5％ 72 76.1 Example 7 9 10 0.1 1％ 9 9.5 Comparative Example 1 40 50 0.5 1％ 40 43.2 Comparative Example 2 49 50 0.5 1％ 49 52.9 Comparative Example 3 45 50 0 0％ 45 48.6

[0072] Table 2

[0073] M (SOC＝0) %]] M (SOC＝100％) %]] M SOC %]] Cycling performance Example 1 88 95.0 88 75.3％ Example 2 90 97.2 90 85.1％ Example 3 98 105.8 98 80.0％ Example 4 91.2 98.5 91.2 85.8％ Example 5 91.2 98.5 91.2 84.3％ Example 6 90 97.2 90 76.9％ Example 7 90 97.2 90 73.4％ Comparative Example 1 80 86.2 80 70.1％ Comparative Example 2 98 105.8 98 63.9％ Comparative Example 3 90 97.2 90 29.3％

[0074] From Table 1 and Table 2, when M SOC When M is less than 85% or greater than (1+L / W) x 100%, the capacity of the battery decreases rapidly, and the service life of the battery and the use time of the electric vehicle are affected. Only when 85%≤M SOC ≤(1+L / W) x 100% is satisfied, the battery exhibits excellent capacity retention, which is beneficial to improve the service life of the battery and the use time of the electric vehicle.

[0075] In addition, M (SOC＝0) of Example 5 is 91.2%, which is within the range of 85% to 100%, and M (SOC＝100％) is 98.5, which is within the range of 94% to (1+L / W) x 100%, and the battery exhibits excellent capacity retention. Because when M (SOC＝0) is less than 85%, the winding core lacks binding force during the entire charging and discharging process, and the graphite falls off from the electrode sheet in repeated expansion and contraction, which causes the performance of the battery to decrease; however, if M (SOC＝100％) is greater than (1+L / W) x 100%, the maximum thickness of the electrode assembly 12 not only exceeds the width of the bottom wall 14, but also directly contacts the separator 2. Because the center of the large face of the electrode assembly 12 expands most severely, after the winding core 121 directly contacts the separator 2, the center of the large face is subjected to the greatest expansion force, and the electrolyte is squeezed out from the center of the large face to form a poor electrolyte area, which easily causes lithium precipitation, and ultimately leads to the performance of the battery to decrease. When M SOC is between the two, the winding core is subjected to a certain binding force, and at the same time, the large face is not poor in liquid due to excessive expansion force, thereby causing the performance of the battery to decrease.

[0076] In combination with Table 1 and Table 2, when the thickness L of the buffer portion 22 is 0 mm, the winding core directly contacts the separator 2 after expansion, which affects the cycle performance, and especially in the later period, the expansion of the winding core is obvious due to the side reaction, and the performance decay is faster. When the thickness L of the buffer portion 22 is 0.2 mm, the winding core slightly contacts the separator after expansion, but in the later period, the expansion of the winding core is obvious due to the side reaction, and the performance decay becomes more obvious. When the thickness L of the buffer portion 22 is 0.5 mm, the gap between the separators provides sufficient expansion space for the winding core, and thus the cycle performance is better.

[0077] The above has carried out the detailed introduction to the battery pack and the electric device provided by the embodiment of the application, the principle and the implementation mode of the application are described in the application by applying specific examples, the above embodiment is only used for helping understanding the technical scheme of the application and its core idea; the ordinary skilled in the art should understand that: it can still modify the technical scheme recorded in the foregoing embodiments, or make equivalent replacement to part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical scheme deviate from the scope of the technical scheme of the embodiments of the application.

Claims

1. A battery pack, characterized by, The battery pack comprises: a plurality of batteries (1); at least one partition plate (2) arranged between adjacent batteries (1); each battery (1) comprises a shell (11) and an electrode assembly (12); the shell (11) has a receiving cavity (13), and the electrode assembly (12) is arranged in the receiving cavity (13); the receiving cavity (13) has a bottom wall (14); the partition plate (2) comprises a plate body (21) and a buffer portion (22) arranged on both sides of the plate body (21); the buffer portion (22) is in abutment with the shell (11); wherein the battery pack satisfies: 85%≤M SOC ≤ (1+L / W) x 100%, and M SOC = D / W, 0.4% < L / W ≤ 6.5%; In the formula, a ratio of a maximum thickness of the electrode assembly (12) of the battery (1) to a width of the bottom wall (14) when the state of charge is 0 to 100% is M SOC , a thickness of the buffer portion (22) is L mm, a width of the bottom wall (14) is W mm, and a maximum thickness of the electrode assembly (12) of the battery (1) when the state of charge is 0 to 100% is D mm. the battery pack further satisfies: 85%≤M (SOC=0) <100%, 94%≤M (SOC=100%) ≤(1+L / W) x 100%, and M (SOC=0) <M (SOC=100%) ; In the formula, the ratio of the maximum thickness of the electrode assembly (12) of the battery (1) when the state of charge is 0 to the width of the bottom wall (14) is M (SOC=0) ; The ratio between the maximum thickness of the electrode assembly (12) of the battery (1) at 100% of state of charge and the width of the bottom wall (14) is M (SOC=100%) ; a thickness L of the buffer portion (22) satisfies: 0 < L ≤ 3; a width W of the bottom wall (14) satisfies: 20 ≤ W ≤ 70.

2. The battery pack of claim 1, wherein: The battery pack further satisfies: M (SOC=0) : M (SOC=100%) = 1:1.05~1.

10.

3. The battery pack of any one of claims 1-2, wherein: The M (SOC=0) The expression for M (SOC=0) = D0 / W; and / or, M (SOC=100%) The expression for M (SOC=100%) = D 100 / W; wherein a maximum thickness of the electrode assembly (12) of the battery (1) at a state of charge of 0 is D0 mm; The maximum thickness of the electrode assembly (12) of the battery (1) at a state of charge of 100% is D 100 mm.

4. The battery pack of claim 3, wherein: the D0 satisfies: 17 ≤ D0 ≤ 70; and / or, The D 100 satisfies: 18.8≤D 100 ≤74.

6.

5. The battery pack of claim 1, wherein: a thickness of the plate body (21) is L1 mm, and satisfies: 0.5 ≤ L / L1 ≤ 2; or 0.65 ≤ L / L1 ≤ 1.

5.

6. The battery pack of claim 1, wherein: the buffer portion (22) is in a ring structure, and a width K of the buffer portion (22) is 4 mm to 20 mm.

7. An electrical device, characterized by The battery pack comprises any one of claims 1-6. The battery pack comprises any one of claims 1-6.

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