Lithium-ion cylindrical battery and electrical apparatus

Abstract

The present invention belongs to the technical field of lithium-ion batteries. Disclosed is a lithium-ion cylindrical battery, comprising a housing, a cylindrical rolled core located in the housing, and an electrolyte. The cylindrical battery satisfies the following relational expression during charging and discharging: (|△a|+|△b|) / ((a+b) / 2)≤3%, a and b being the longest diameter and the shortest diameter, respectively, of the cylindrical battery in a fully discharged state, and △a and △b being change values of the longest diameter and the shortest diameter, respectively, at 0% SOC and 100% SOC. The cylindrical battery provided in the present invention obtains a specific initial internal stress by means of limiting the external deformation amount of the cylindrical battery, reserving a deformation release space for a later formation cycle of the cylindrical battery, and avoiding distortion or even fracture of a local electrode sheet caused by excessive internal stress.

Description

Lithium ion cylindrical battery and electric device TECHNICAL FIELD

[0001] The present application belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion cylindrical battery and an electric device. BACKGROUND

[0002] With the improvement of the level of science and technology, high-power electrical appliances gradually popularize in people's work and life, and the safety problem of secondary batteries used by electrical appliances is increasingly concerned by people. In the existing cylindrical battery products on the market, due to the large internal resistance, a large amount of heat is lost during the discharge process of the battery, resulting in a low energy utilization rate. Due to the design problem of the battery structure and system, the temperature rise coefficient of the battery is also high. In the same temperature range, the battery discharge rate is low.

[0003] The main component of the shell of the cylindrical battery is iron, and its huge mechanical strength ensures the safety of the battery. However, due to the expansion of the pole piece and the gas production of the system during the battery cycle process, the shell will bear a large stress, and long-term stress and strain will cause the steel shell to deform or even crack, reducing the cycle performance and safety of the battery. The closer the appearance of the battery is to a circle, the better the strain resistance of the battery; in addition, through reasonable optimization of the system, reasonable expansion of the pole piece and reasonable gas production of the system can reduce the deformation of the winding core shape of the battery under different SOC states, greatly improving the fatigue resistance of the winding core; in addition, the main mechanical support in the cylindrical battery comes from the copper foil and aluminum foil, and designing a pole piece with a certain elongation range will help to improve the mechanical strength of the winding core and ensure the uniformity of the winding core structure under strain. Thus, the cycle and safety performance of the battery are improved.

[0004] Therefore, it is necessary to develop a new type of cylindrical battery that comprehensively considers the deformation range, gas production and elongation, so as to solve the problem of the existing lithium ion cylindrical battery that the internal resistance is too large and the temperature rise coefficient is high. SUMMARY

[0005] The present application aims to provide a lithium ion cylindrical battery and an electric device.

[0006] The technical solution of the present application is as follows:

[0007] A lithium ion cylindrical battery comprises a shell, a cylindrical winding core located in the shell and an electrolyte, and the cylindrical battery satisfies the following relationship during the charging and discharging process: (|△a|+|△b|) / ((a+b) / 2)≤3%,

[0008] wherein a and b are the longest diameter and the shortest diameter of the cylindrical battery in the full discharge state respectively; △a and △b are the change values of the longest diameter and the shortest diameter under 0% and 100% SOC states respectively.

[0009] Further, the diameter ratio of each section of the cylindrical battery satisfies the following relationship: |H1-H2|+|H2-H3|+|H1-H3|≤12%,

[0010] wherein in the case of full charging of the battery, the length direction of the cylindrical battery from the bottom to the top is divided into 6 equal parts, and the diameters of the directions corresponding to the center positions of the 3 equal parts close to the bottom are respectively tested, and |a-b| / (a+b) of each position is respectively calculated, and the obtained values are denoted as H1, H2, H3.

[0011] Further, the gas content ratio of the cylindrical battery satisfies the following relationship: 1.05≤3Vg / V≤2.1,

[0012] wherein the total volume of the cylindrical battery is V mL, and the internal gas content at room temperature is Vg mL.

[0013] Further, the material ductility of the cylindrical battery satisfies the following relationship: 6%≤E Cu +E Al ≤12%,

[0014] wherein the E Cu is the ductility of the copper foil, and the E Al is the ductility of the aluminum foil.

[0015] Further, the cylindrical battery comprises a positive electrode sheet, a negative electrode sheet and a separator between the two, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material coating on at least one surface of the positive electrode current collector, the positive electrode current collector comprises a positive electrode active material coated area and a positive electrode active material uncoated area, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material coating on at least one surface of the negative electrode current collector, the negative electrode current collector comprises a negative electrode active material coated area and a negative electrode active material uncoated area; wherein a part of the positive electrode active material uncoated area is used as a positive electrode tab, and the positive electrode active material uncoated area accounts for 2-15% of the surface area of the positive electrode current collector; a part of the negative electrode active material uncoated area is used as a negative electrode tab, and the negative electrode active material uncoated area accounts for 2-15% of the surface area of the negative electrode current collector; and the capacity N / P ratio of the negative electrode sheet to the positive electrode sheet is 1.02-1.15.

[0016] Further, the positive electrode sheet comprises a positive electrode active material, a binder and a conductive agent, the positive electrode active material comprises one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, wherein the chemical formula of lithium nickel cobalt manganese oxide is Li a Ni x Co y Mn z M bO2, 0.8 < a < 1.2, 0.81 ≤ x ≤ 0.95, 0.1 ≤ y < 0.4, 0.05 ≤ z < 0.4, 0 ≤ b ≤ 0.1, M comprises any one or more combinations of Zr, Ti, W, Al, Sr, La, Nd, B.

[0017] Further, the negative electrode sheet comprises a negative electrode active material, a binder and a conductive agent, the negative electrode active material comprises at least two of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon-oxygen material and silicon-carbon material, and the mass percentage of silicon in the negative electrode active material is 2-30%.

[0018] Further, at least one edge area of the positive electrode active material coating area is coated with an inorganic ceramic coating, the inorganic ceramic coating comprises any one or more combinations of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron trioxide, boehmite and calcite.

[0019] Further, the average particle size Dv50 of the inorganic material particles in the inorganic ceramic coating is 0.5-3 μm, the width direction of the inorganic ceramic coating is arranged along the width direction of the positive electrode sheet, and the width of the inorganic ceramic coating accounts for 1-3% of the entire positive electrode sheet width.

[0020] Further, the electrolyte comprises a solvent, a lithium salt and an additive, the solvent comprises any one or more combinations of dimethyl carbonate, diethyl carbonate, ethylene carbonate and methyl ethyl carbonate, the additive comprises any one or more combinations of propylene carbonate, butene carbonate, ethyl acetate and propyl propionate, and the lithium salt comprises any one or more combinations of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium bisfluorosulfonylimide and lithium bis-trifluoromethylsulfonylimide.

[0021] Another technical solution of the present application is:

[0022] A power device comprises the lithium ion cylindrical battery as described above.

[0023] The present application provides a lithium ion cylindrical battery and a power device, and the beneficial effects are:

[0024] 1. By limiting the appearance deformation of the cylindrical battery, a specific initial internal stress is obtained, and a deformation release space is reserved for the later formation cycle of the cylindrical battery, so that the local sheet is prevented from being twisted or even broken due to excessive internal stress.

[0025] 2. By further limiting the diameter ratio of each section of the cylindrical battery, the gas production and the elongation, the deformation release space is reserved after the stress changes in the later stage of the cylindrical battery, so as to overcome the stress change problems caused by the subsequent material activation, lithium extraction reaction, negative electrode film formation of electrolyte, electrode expansion, elongation and gas generation;

[0026] 3. By adopting a battery with a specific internal stress and cooperating with the full tab design, the material and shape of the lithium ion cylindrical battery are further optimized, so as to obtain a lithium ion cylindrical battery with high rate and low temperature rise. In the same temperature range, the temperature rise coefficient of 10C discharge is low, the heat generation is less, the cycle performance is better under the conventional 1C / 1C rate, the cycle retention rate is 86-99.1% after 600 cycles, the cycle performance under the cycle condition of 3C / 6C is significantly improved, the safety performance is high, and the passing rate of the thermal box experiment is greater than or equal to 80%. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 shows the winding diagram of the electrode sheet and the separator of the cylindrical battery involved in some embodiments, wherein (a) is a perspective view and (b) is a sectional view;

[0028] Fig. 2 shows the longest diameter corresponding to a value and the shortest diameter corresponding to b value diagram of the cylindrical battery involved in some embodiments, wherein (a) is a perspective view and (b) is a sectional view;

[0029] Fig. 3 shows the longest diameter and the shortest diameter diagram of the cylindrical battery at different positions involved in some embodiments;

[0030] Fig. 4 shows the shell and winding core assembly diagram of the lithium ion cylindrical battery involved in some embodiments;

[0031] Fig. 5 shows the positive electrode sheet coating diagram of the lithium ion cylindrical battery involved in some embodiments;

[0032] Fig. 6 shows the negative electrode sheet coating diagram of the lithium ion cylindrical battery involved in some embodiments.

[0033] In the figure: 1, winding core; 2, separator; 3, negative electrode sheet; 4, positive electrode sheet; 5, positive electrode end; 6, negative electrode end; 7, shell; 31, negative electrode coating area; 32, negative electrode uncoated area; 40, positive electrode tab area; 41, positive electrode uncoated area; 42, positive electrode coating area; 43, ceramic edge coating area. DETAILED DESCRIPTION

[0034] In the initial stage of battery assembly, there is an initial internal stress, and as the formation proceeds, the material starts to activate and extract lithium, the electrolyte forms a film on the negative electrode interface, etc. These processes are accompanied by electrode expansion and elongation, and the reaction is accompanied by gas generation. Therefore, after the formation, distribution and other steps, the electrode of the battery is elongated and deformed.

[0035] At least one embodiment provides a lithium ion cylindrical battery, comprising a shell, a cylindrical winding core located in the shell and an electrolyte, the cylindrical battery satisfies the following relationship during charging and discharging: (|△a|+|△b|) / ((a+b) / 2)≤3%,

[0036] Please refer to FIG. 2, where a and b are the longest diameter and the shortest diameter of the cylindrical battery in full discharge state respectively; △a and △b are the change values of the longest diameter and the shortest diameter in 0% and 100% SOC state respectively.

[0037] The test method of a and b is as follows: first, the cylindrical battery is discharged at a discharge rate of 0.2C to full discharge, and the plastic shell is stripped off, and projected in the vertical direction to obtain a and b values. Mark the positions corresponding to a and b values on the cylindrical battery. The battery is charged at a charge rate of 0.2C to full charge, and the constant voltage charging is carried out until the current is less than 0.05C. Project again, and test at the original a and b positions to obtain △a and △b. The above method is tested on 3 parallel samples, and the average value is obtained.

[0038] In the present embodiment, specifically, the cylindrical battery also satisfies the following relationship: |H1-H2|+|H2-H3|+|H1-H3|≤12%,

[0039] Please refer to FIG. 3, where the cylindrical battery is divided into 6 equal parts from the bottom to the top in the length direction in the full charge state of the battery, and the diameters of the center positions of the three equal parts close to the bottom are tested respectively, and |a-b| / (a+b) of each position is calculated respectively, and the obtained values are denoted as H1, H2 and H3.

[0040] Wherein, the full charge state is that the battery is charged to 100% SOC, the full discharge state is that the battery is discharged to 0% SOC, and the charge and discharge current is 0.2C.

[0041] The generation of gas is the first stage of stress change, the more the amount of generated gas, the greater the internal stress, and the more significant the extension deformation of the pole piece. The greater the internal stress, the more significant the extension deformation of the pole piece. With the subsequent cycle, the pole piece repeatedly expands, shrinks and extends. If the extension rate of the pole piece is too large, the deformation will be too large, causing the internal stress of the battery to be too large. If the extension is too small, the deformation cannot be effectively dispersed and released, and the accumulation in the thickness direction is too large, causing the local pole piece to twist or even break.

[0042] In the present embodiment, specifically, the cylindrical battery also satisfies the following relationship: 1.05≤3Vg / V≤2.1,

[0043] Wherein the total volume of the cylindrical battery is V mL, and the internal gas content of the cylindrical battery at room temperature is Vg mL. The total volume V of the cylindrical battery is calculated by measuring the diameter and height of the battery; for the internal gas content Vg, it is tested by a gas replacement method gas pycometer tester.

[0044] In this embodiment, specifically, the material ductility of the cylindrical battery also satisfies the following relationship: 6%≤E Cu +E Al ≤12%,

[0045] Wherein the E Cu is the ductility of the copper foil, and the E Al is the ductility of the aluminum foil, wherein the ductility refers to the national standard GB / T 22638.11-2023.

[0046] Referring to FIGS. 5 and 6, the cylindrical battery includes a positive electrode sheet, a negative electrode sheet, and a separator located therebetween, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material coating layer located on at least one surface of the positive electrode current collector, the positive electrode current collector includes a positive electrode active material coated area and a positive electrode active material uncoated area, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material coating layer located on at least one surface of the negative electrode current collector, the negative electrode current collector includes a negative electrode active material coated area and a negative electrode active material uncoated area; wherein a part of the positive electrode active material uncoated area is used as a positive electrode tab, and the positive electrode active material uncoated area accounts for 2-15% of the surface area of the positive electrode current collector; a part of the negative electrode active material uncoated area is used as a negative electrode tab, and the negative electrode active material uncoated area accounts for 2-15% of the surface area of the negative electrode current collector; and the capacity N / P ratio of the negative electrode sheet to the positive electrode sheet is 1.02-1.15; the positive electrode active material uncoated area used as the positive electrode tab and the negative electrode active material uncoated area used as the negative electrode tab constitute a full tab.

[0047] At least one embodiment provides an electrical device comprising a lithium ion cylindrical battery as described above.

[0048] In order to make the above objectives, features and advantages of the present application more apparent, the technical solutions of the present application will be further described below in conjunction with embodiments. However, the present application is not limited to the listed embodiments, and should also include any known changes within the scope of the claimed rights of the present application.

[0049] As used herein, "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the implementation can be included in at least one implementation of the present application. The appearances of "in one embodiment" or "in an embodiment" in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of other embodiments.

[0050] Test battery preparation method:

[0051] Positive electrode sheet manufacturing method:

[0052] The positive electrode sheet comprises a positive electrode current collector aluminum foil and a positive electrode coating layer coated on both sides of the aluminum foil; wherein, according to the weight percentage, the positive electrode coating layer comprises 97% of lithium nickel cobalt manganese oxide (811 positive electrode), 0.4% of single-walled carbon nanotube conductive agent, 1.6% of Super-P (conductive carbon black) conductive agent, and 1% of polyvinylidene fluoride PVDF binder; the above-mentioned substances are added into NMP to form a positive electrode slurry by stirring, the solid content is 60%, and the positive electrode slurry is coated on the positive electrode current collector to form the positive electrode sheet.

[0053] Negative electrode sheet manufacturing method:

[0054] The negative electrode sheet comprises a negative electrode current collector copper foil and a negative electrode coating layer coated on both sides of the copper foil, according to the weight percentage, the negative electrode coating layer comprises 96% of artificial graphite, 1.0% of conductive agent acetylene black, 1% of thickening agent CMC, and 2% of negative electrode binder polyacrylate LA133; the above-mentioned substances are added into deionized water to form a negative electrode slurry by stirring, the solid content is 40%, and the negative electrode slurry is coated on the negative electrode current collector to form the negative electrode sheet.

[0055] Electrolyte manufacturing method:

[0056] Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed according to a volume ratio of 1:1:1 to obtain an organic solvent, and then fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0057] Separator manufacturing method:

[0058] The separator comprises a high-porosity power separator, a base film PE with a thickness of 9 μm, two sides of ceramic coating with a thickness of 1 μm, and a PVDF coating layer with a thickness of 1 μm, and the air permeability of the separator is ≥80 s / 100 mL.

[0059] Assembly method:

[0060] After the positive electrode sheet and the negative electrode sheet are respectively roll-cut and die-cut, the positive electrode sheet, the negative electrode sheet, and the separator are simultaneously wound to obtain a cylindrical battery roll core body, the roll core body tab is welded with an electrical connection sheet, and the roll core body is loaded into a battery shell, and after completing the liquid injection, sealing, and formation processes, an experimental battery as shown in FIG. 4 is obtained.

[0061] Example 1: A 21700 lithium ion cylindrical battery preparation method is shown in the following steps.

[0062] The positive electrode sheet comprises a positive electrode current collector aluminum foil and a positive electrode coating layer coated on both sides of the aluminum foil; wherein, the positive electrode coating layer comprises 97% of lithium nickel cobalt manganese oxide (811 positive electrode), 0.4% of single-walled carbon nanotube conductive agent, 1.6% of Super-P (conductive carbon black) conductive agent, and 1% of polyvinylidene fluoride (PVDF) binder, calculated by weight percentage; the above-mentioned substances are added into NMP for stirring to form a positive electrode slurry with a solid content of 60%, which is coated on the positive electrode current collector to form the positive electrode sheet.

[0063] The negative electrode sheet comprises a negative electrode current collector copper foil and a negative electrode coating layer coated on both sides of the copper foil; wherein, the negative electrode coating layer comprises 96% of artificial graphite, 1.0% of conductive agent acetylene black, 1% of thickening agent CMC, and 2% of negative electrode binder polyacrylate LA133, calculated by weight percentage; the above-mentioned substances are added into deionized water for stirring to form a negative electrode slurry with a solid content of 40%, which is coated on the negative electrode current collector to form the negative electrode sheet.

[0064] Ethylene carbonate (EC), methyl ethyl carbonate (EMC), and diethyl carbonate (DEC) are mixed in a volume ratio of 1:1:1 to obtain an organic solvent, and then the fully dried lithium salt LiPF6 is dissolved in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0065] The separator comprises a high-porosity power separator, a base film PE with a thickness of 9 μm, a ceramic coating layer on both sides with a thickness of 1 μm, and a PVDF coating layer with a thickness of 1 μm, and the air permeability of the separator is ≥80 s / 100 mL.

[0066] Referring to FIG. 1, after the positive electrode sheet and the negative electrode sheet are respectively rolled, cut, and die-cut, they are wound together with the separator. The positive electrode sheet, the negative electrode sheet, and the separator are wound by a winding machine to form a winding core. The winding core is cut and stacked to form positive and negative electrode tabs. The positive and negative bus bars are respectively welded with the winding core. The negative bus bar is welded with the steel shell. The positive bus bar is placed on the insulating sheet, and the positive bus bar is welded with the cap. A 21700 cylindrical battery winding core body is obtained. The battery winding core body is loaded into a battery shell. After liquid injection, sealing, and formation processes, an experimental battery is obtained.

[0067] Referring to the above process, the size is changed to obtain experimental batteries of types 4680, 4695, 18650, and 46120.

[0068] Other related parameter settings involved in Examples 1-12 and Comparative Examples 1-5 are shown in Table 1 below:

[0069] Table 1 Other related parameters of Examples 1-12 and Comparative Examples 1-5

[0070] Firstly, the cylindrical battery is discharged at a discharge rate of 0.2C, and the plastic shell is stripped off, and the a, b values are obtained by projection in the vertical direction, and the positions corresponding to the a, b values are marked on the cylindrical battery; the battery is fully charged at a charge rate of 0.2C, and the constant voltage charging is carried out until the current is less than 0.05C. And project again, and test at the original a, b position to obtain Δa and Δb. The above method is tested on 3 parallel samples, and the average value is obtained.

[0071] The a, b related data involved in examples 1-12 and comparative examples 1-5 are as follows in table 2:

[0072] Table 2 a, b related data of examples 1-12 and comparative examples 1-5

[0073] The cylindrical battery does not present a complete circle in most cases, but there is stress and strain deformation. This formula reflects the degree of change of the shape of the cylindrical battery from full discharge to full charge.

[0074] When the degree of change is too large, such as more than 3%, it indicates that the stress and strain is too large, and the accumulation of internal stress and strain will cause the deformation of the pole piece, the pores of the active material layer will be compressed, and even the deformation and fracture of the structural support will be caused, thereby degrading the cycle performance and safety performance of the battery.

[0075] Generally, when the deformation exceeds 3%, it indicates that the internal stress of the battery is too large, and many pores of the active material layer are compressed, and the structure is in a metastable state.

[0076] In the full charge state of the battery, the length direction from the bottom to the top is divided into 6 equal parts, and the diameters of the center positions of the 3 equal parts close to the bottom in the respective directions are tested respectively, and the |a-b| / (a+b) of each position is calculated respectively, and the obtained values are denoted as H1, H2, H3.

[0077] The H1, H2, H3 related data involved in examples 1-12 and comparative examples 1-5 are as follows in table 3:

[0078] Table 3 H1, H2, H3 related data of examples 1-12 and comparative examples 1-5

[0079] This parameter indicates the uniformity of the cylindrical battery structure. Generally within 12%, it indicates that the structure of the cylindrical battery at different height sections is relatively uniform, and the internal stress is uniformly dispersed, so that the cycle and safety performance is guaranteed.

[0080] But when the value exceeds 12%, it indicates that the uniformity of the battery is poor, the stress and strain of the local area are greater than those of other positions, the internal stress of the battery cannot be uniformly dispersed, and the local area is significantly degraded, thereby reducing the cycle and safety performance of the overall battery.

[0081] Capacity retention test, 25°C, 1C / 1C

[0082] Cycle performance and center hole collapse test after cycling (for example, test a cylindrical battery with a high-nickel positive electrode and a graphite mixed silicon negative electrode, and modify the voltage interval for testing for other types of batteries)

[0083] Take one cylindrical battery, such as 217005Ah, and place it in a 25°C constant temperature box for more than 4h, and test according to the following steps:

[0084] (1) Discharge the battery to 2.5V cutoff under the condition of 0.1C constant current, and stand for 5min;

[0085] (2) Charge the battery to 4.2V cutoff under the condition of 0.2C constant current, and charge to 0.05C cutoff under constant voltage, and stand for 5min;

[0086] (3) Discharge the battery to 2.5V cutoff under the condition of 0.2C constant current, and stand for 5min, and read the capacity value C0 at this time;

[0087] (4) Charge the battery to 4.2V under the condition of 1.0C constant current, and charge to 0.05C cutoff under constant voltage, and stand for 5min;

[0088] (5) Discharge the battery to 2.5V cutoff under the condition of 2.0C constant current, and stand for 5min;

[0089] (6) Repeat steps (4) and (5) 600 times;

[0090] (7) The cycle performance of a single battery, i.e. the capacity retention rate, is obtained by the ratio of the 600th discharge capacity to the 1st discharge capacity of steps (4) and (5).

[0091] The capacity retention related data involved in Examples 1-12 and Comparative Examples 1-5 are as follows in Table 4:

[0092] Table 4 Capacity retention data of Examples 1-12 and Comparative Examples 1-5

[0093] Hot box test, take one battery, and place it in a 25°C constant temperature box for more than 4h, and test according to the following steps:

[0094] (1) the battery is discharged at a constant current to 2.5V cut-off under the condition of 0.1C, and is left for 5min;

[0095] (2) the battery is charged at a constant current to 4.2V cut-off under the condition of 0.2C, and is charged at a constant voltage to 0.05C cut-off, and is left for 5min;

[0096] (3) the battery is placed into a thermal oven, the heating rate is set to 5K / min, and is heated to 130℃, and is kept for 1h, and then the heating is stopped, and is cooled to below 30℃ by self-heating;

[0097] (4) the battery is not considered to pass if it does not catch fire and does not emit smoke, otherwise it is not considered to pass, at least 5 batteries are tested, and the pass rate is recorded;

[0098] (5) after the test is completed, the battery is considered to pass if it does not leak, catch fire or explode, that is, the thermal oven pass rate.

[0099] The data related to the thermal oven pass rate in the examples 1-12 and the comparative examples 1-5 are as follows in Table 5:

[0100] Table 5 Thermal oven pass rate data of examples 1-12 and comparative examples 1-5

[0101] In summary, the lithium ion cylindrical battery and the electric device of the present application pass by limiting the appearance deformation of the cylindrical battery, obtaining a specific initial internal stress, reserving deformation release space for the later formation cycle of the cylindrical battery, avoiding excessive internal stress leading to local tab distortion or even fracture; further limiting the diameter ratio of each interval of the cylindrical battery, the gas generation amount and the elongation, reserving deformation release space for the change of the stress of the cylindrical battery after the later stress change, to overcome the stress change problem of the subsequent material activation, lithium extraction reaction, negative electrode film formation of electrolyte, tab expansion, elongation and gas generation; the battery with specific internal stress is combined with full-tab design, further optimizing the material and shape of the lithium ion cylindrical battery, thereby obtaining a lithium ion cylindrical battery with high rate and low temperature rise, which has low temperature rise coefficient and less heat generation at the same temperature range, has better cycle performance at the conventional 1C / 1C rate, has 600 cycle retention rate of 86-99.1%, and has significantly improved cycle performance under the cycle condition of 3C / 6C, has high safety performance, and the thermal oven test pass rate is greater than or equal to 80%.

[0102] It should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A lithium ion cylindrical battery comprising a case, a cylindrical jelly-roll core located in the case, and an electrolyte, characterized by, The cylindrical battery satisfies the following relationship during charging and discharging: (|△a|+|△b|) / ((a+b) / 2)≤3%, wherein a is the longest diameter of the cylindrical battery in the full discharge state; b is the shortest diameter of the cylindrical battery in the full discharge state; △a is the change value of the longest diameter under 0% and 100% SOC states; △b is the change value of the shortest diameter under 0% and 100% SOC states.

2. The lithium-ion cylindrical battery according to claim 1, characterized by, The diameter ratio of each section of the cylindrical battery satisfies the following relationship: |H1-H2|+|H2-H3|+|H1-H3|≤12%, wherein the length direction of the cylindrical battery from the bottom to the top is divided into 6 equal parts, and the diameters of the center positions of the 3 equal parts close to the bottom are tested respectively, and |a-b| / (a+b) of each position is calculated respectively, and the obtained values are denoted as H1, H2, H3.

3. The lithium-ion cylindrical battery according to claim 1, characterized by, The gas content ratio of the cylindrical battery satisfies the following relationship: 1.05≤3Vg / V≤2.1, wherein the total volume of the cylindrical battery is V mL, and the internal gas content at room temperature is Vg mL.

4. The lithium-ion cylindrical battery according to claim 1, characterized by, The material ductility of the cylindrical battery satisfies the following relationship: 6%≤E Cu +E Al ≤12% wherein said E Cu is the elongation of the copper foil, said E Al is the elongation of the aluminum foil.

5. The lithium-ion cylindrical battery according to any one of claims 1 to 4, characterized by, The cylindrical battery comprises a positive electrode sheet, a negative electrode sheet and a separator between the two, the positive electrode sheet comprises a positive electrode current collector and a positive electrode active material coating on at least one surface of the positive electrode current collector, the positive electrode current collector comprises a positive electrode active material coating area and a positive electrode active material non-coating area, the negative electrode sheet comprises a negative electrode current collector and a negative electrode active material coating on at least one surface of the negative electrode current collector, and the negative electrode current collector comprises a negative electrode active material coating area and a negative electrode active material non-coating area; wherein a part of the positive electrode active material non-coating area is used as a positive electrode tab, and the positive electrode active material non-coating area accounts for 2-15% of the surface area of the positive electrode current collector; a part of the negative electrode active material non-coating area is used as a negative electrode tab, and the negative electrode active material non-coating area accounts for 2-15% of the surface area of the negative electrode current collector; and The N / P ratio of the capacity of the negative electrode sheet to the positive electrode sheet is 1.02-1.

15.

6. The lithium-ion cylindrical battery according to claim 5, characterized by, The positive electrode sheet includes a positive electrode active material, a binder, and a conductive agent, the positive electrode active material includes one or more of lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, wherein the chemical formula of the lithium nickel cobalt manganese oxide is Li a Ni x Co y Mn z M b O2, 0.8 < a < 1.2, 0.81 ≤ x ≤ 0.95, 0.1 ≤ y < 0.4, 0.05 ≤ z < 0.4, 0 ≤ b ≤ 0.1, M includes any one or more combinations of Zr, Ti, W, Al, Sr, La, Nd, B.

7. The lithium-ion cylindrical battery according to claim 5, characterized by, The negative electrode sheet comprises a negative electrode active material, a binder and a conductive agent, the negative electrode active material comprises at least two of artificial graphite, natural graphite, mesocarbon microbeads, soft carbon, hard carbon, silicon-oxygen material and silicon-carbon material, and the mass percentage of silicon in the negative electrode active material is 2-30%.

8. The lithium-ion cylindrical battery according to claim 5, characterized by, At least one edge area of the positive electrode active material coating area is coated with an inorganic ceramic coating, the inorganic ceramic coating comprises any one or a combination of two or more of aluminum oxide, manganese dioxide, magnesium oxide, silicon dioxide, titanium dioxide, zirconium dioxide, zinc oxide, iron trioxide, boehmite and calcite; and The average particle size Dv50 of the inorganic material particles in the inorganic ceramic coating is 0.5-3 μm, the width direction of the inorganic ceramic coating is arranged along the width direction of the positive electrode tab, and the width of the inorganic ceramic coating accounts for 1-3% of the entire positive electrode tab width.

9. The lithium-ion cylindrical battery according to claim 5, characterized by, The electrolyte includes a solvent, a lithium salt, and an additive, the solvent includes a combination of any one or more of dimethyl carbonate, diethyl carbonate, ethylene carbonate, and methyl ethyl carbonate, the additive includes a combination of any one or more of propylene carbonate, butene carbonate, ethyl acetate, and propyl propionate, and the lithium salt includes a combination of any one or more of lithium hexafluorophosphate, lithium difluorophosphate, lithium difluoro oxalate borate, lithium bisfluorosulfonylimide, and lithium bis-trifluoromethylsulfonylimide.

10. An electrical device, characterized by A lithium-ion cylindrical battery including the lithium-ion cylindrical battery according to any one of claims 1 to 9.

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