CN117638251A

CN117638251A - Electrochemical device, battery pack and electric equipment

Info

Publication number: CN117638251A
Application number: CN202311828023.7A
Authority: CN
Inventors: 童衍辰; 吴克成; 陈雨
Original assignee: Xiamen Xinnengda Technology Co Ltd
Current assignee: Xiamen Xinnengda Technology Co Ltd
Priority date: 2023-12-27
Filing date: 2023-12-27
Publication date: 2024-03-01

Abstract

The application discloses an electrochemical device, a battery pack and electric equipment. The electrochemical device includes a case and an electrode assembly accommodated in the case. The electrode assembly comprises a first electrode plate, a second electrode plate and a diaphragm, wherein the first electrode plate, the diaphragm and the second electrode plate are laminated and wound along the winding direction, one of the first electrode plate and the second electrode plate is an anode electrode plate, and the other is a cathode electrode plate. The first pole piece comprises a first current collector and a first active substance arranged on the first current collector, the first current collector comprises a first main body area and a first empty foil area, the first active substance is arranged in the first main body area, and the arrangement direction of the first main body area and the first empty foil area is perpendicular to the winding direction. The first empty foil region includes a first flattened region, the first flattened region being remote from the first body region. The electrochemical device can increase overcurrent capacity and reduce energy loss when discharging at a high rate of 15-20C by arranging the first rubbing zone, so that the electrochemical device can have higher discharge capacity.

Description

Electrochemical device, battery pack and electric equipment

Technical Field

The present application relates to the field of battery technology, and more particularly, to an electrochemical device, a battery pack, and an electrical consumer.

Background

With the widespread use of electrochemical devices (e.g., lithium ion batteries) in various types of electronic products, users have also placed increasing demands on the performance of electrochemical devices. How to improve the discharge performance of an electrochemical device has been a research direction in the industry.

Disclosure of Invention

The application provides an electrochemical device, a battery pack and electric equipment, which can improve discharge performance.

In a first aspect, embodiments of the present application provide an electrochemical device including a case and an electrode assembly received in the case. The electrode assembly comprises a first electrode plate, a second electrode plate and a diaphragm, wherein the first electrode plate, the diaphragm and the second electrode plate are laminated and wound along the winding direction, one of the first electrode plate and the second electrode plate is an anode electrode plate, and the other is a cathode electrode plate. The first pole piece comprises a first current collector and a first active substance arranged on the first current collector, the first current collector comprises a first main body area and a first empty foil area, the first active substance is arranged in the first main body area, and the arrangement direction of the first main body area and the first empty foil area is perpendicular to the winding direction. The first empty foil region includes a first flattened region, the first flattened region being remote from the first body region.

The electrochemical device is configured to:

in response to the electrochemical device having 100% SOC performing a discharge operation at a first discharge rate at a first ambient temperature, continuing the discharge operation until the SOC of the electrochemical device is 0%, the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device being greater than or equal to 90%;

wherein the first ambient temperature is 22-28 ℃, and the first discharge multiplying power is in the range of 15-20 ℃.

The electrochemical device can increase overcurrent capacity by arranging the first rubbing area, has smaller resistance, has lower temperature rise when discharging at a high multiplying power of 15-20C, and is beneficial to reducing energy loss, so that the electrochemical device can have higher discharge capacity, provides more electric energy for electric equipment, and improves the discharge performance of the electrochemical device.

In one or more alternative embodiments, the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 95%. The electrochemical device can have higher discharge capacity when discharging at a high rate of 15-20C, and provides more electric energy for electric equipment.

In one or more alternative embodiments, the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 98%. The electrochemical device can have higher discharge capacity when discharging at a high rate of 15-20C, and provides more electric energy for electric equipment.

In one or more of the above alternative embodiments, the first discharge rate is in the range of 17.5C-20C. When the discharge is carried out at a high rate of 17.5-20C, the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, so that more electric energy can be provided for electric equipment.

In one or more alternative embodiments, the first ambient temperature is 25 ℃.

In one or more of the above optional embodiments, along the width direction of the first pole piece after being unfolded, the size of the first empty foil area is W1, and the total size of the first current collector is W2, where W1 and W2 satisfy: W1/W2 is more than or equal to 0.05 and less than or equal to 0.1.

The W1/W2 is limited to be larger than or equal to 0.05, so that the first empty foil area has larger width, connection between the first empty foil area and other conductive structures is facilitated, stress of the first active substance is reduced during rubbing, and risks of deformation and powder dropping of the first active substance are reduced. By limiting W1/W2 to less than or equal to 0.1, more space can be reserved for the first active material, reducing energy density losses.

In one or more of the above alternative embodiments, the first flattened area has a dimension W4, 0.6-W4/W1-0.95 along the width of the first pole piece after deployment.

The W4/W1 is limited to be larger than or equal to 0.6, so that the compression area of the first empty foil area in the rubbing process can be increased, the axial size of the electrode assembly is reduced, the space utilization rate is improved, and the first rubbing area is more compact. Defining W4/W1 to be less than or equal to 0.95 may reduce the force transferred to the first active material during the flattening process, reducing the risk of the first active material falling off.

In one or more of the above alternative embodiments, the corner of the outer end of the first empty foil area in the winding direction is provided with a first cut; and along the length direction of the unfolded first pole piece, the size of the first incision is La. La and W1 satisfy: la/W1 is more than or equal to 0.2 and less than or equal to 4.

La/W1 is limited to be more than or equal to 0.2, so that accumulation of empty foil materials can be reduced in the rolling process, the risk of puncturing an insulating piece coating the first empty foil area is reduced, and the safety is improved. Limiting La/W1 to less than or equal to 4 can reduce the impact of the first notch on the overcurrent capability of the first blank foil area.

In one or more of the above alternative embodiments, the first incision has a dimension W3 along a width direction of the first pole piece after being unfolded; w3 and W1 satisfy: W3/W1 is more than or equal to 0.2 and less than or equal to 1.

The W3/W1 is limited to be larger than or equal to 0.2, so that the accumulation of empty foil materials can be reduced in the rolling process, the risk of puncturing an insulating piece coating the first empty foil area is reduced, and the safety is improved. Limiting W3/W1 to less than or equal to 1 can reduce the risk of the first incision opening into the first body region, reducing the loss of the first active material.

In one or more of the above alternative embodiments, along the length direction of the first pole piece after being unfolded, the first empty foil region has a size L1, and the first main body region has a size L2, where L1 and L2 satisfy: L1/L2 is more than or equal to 0.8 and less than or equal to 1.

The first empty foil area has a larger overcurrent area, and when the electrochemical device discharges at a high rate, the first empty foil area can pass through a larger current, so that heat generation of the first empty foil area is reduced, and the risk of fusing of the first empty foil area is reduced.

In one or more of the above alternative embodiments, the electrochemical device further includes an insulating member surrounding the outer side of the first rolling region, and an overlapping region is provided at a surrounding interface of the insulating member, the overlapping region avoiding an outer end of the first rolling region in a winding direction.

The insulating sheet may separate the first flattened area from the housing to reduce the risk of short circuits. The insulating sheet can also draw in the first rubbing zone from the periphery, reducing the risk of the first rubbing zone spreading out. The outer end of the first rubbing zone along the winding direction is not overlapped with the overlapped area, so that the problem that the energy density is reduced due to the increase of the radial dimension caused by the increase of the thickness after overlapping is solved.

In one or more of the above alternative embodiments, the electrochemical device further includes a first electrode terminal provided to the case, and a current collecting tray connecting the first flattening region and the first electrode terminal, the current collecting tray being provided with a through hole.

The first rubbing area is provided with a compact end face, and the first rubbing area is connected with the current collecting disc, so that the connection strength can be improved. In the liquid injection process, electrolyte can pass through the through holes and infiltrate the electrode assembly, so that wettability is improved. The electrode assembly may release gas when the electrochemical device fails due to overheating, overcharge, short-circuiting, or other reasons; through the through hole, can provide the passageway for gas to discharge the outside of electrochemical device fast, reduce the explosion risk.

In one or more alternative embodiments above, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector, the positive electrode active material including Li _1+a Ni _x1 Co _y1 Mn _z1 O ₂ Or Li (lithium) ₁₊ _a Ni _x2 Co _y2 Al _z2 O ₂ At least one of them. x1 and x2 are both greater than or equal to 0.8, y1 and y2 are both greater than 0, z2 and z3 are both greater than 0, x1+y1+z1=1, x2+y2+z2=1, -0.05.ltoreq.a.ltoreq.0.2.

In one or more alternative embodiments, x1 and x2 are each greater than or equal to 0.9.

In one or more of the above alternative embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material including artificial graphite and/or natural graphite.

In one or more alternative embodiments, the electrochemical device further includes an electrolyte contained within the housing. The electrolyte comprises 12-16% by mass of lithium hexafluorophosphate and 0.8-1.5% by mass of fluoroethylene carbonate based on the mass of the electrolyte. Fluoroethylene carbonate is used as an electrolyte additive, is favorable for improving the performance of an SEI film, forms a compact structure layer without increasing impedance, can prevent electrolyte from further decomposition, and improves the discharge performance of an electrochemical device.

In one or more alternative embodiments, the electrochemical device includes a cylindrical cell. The cylindrical battery cell has mature production process, higher product yield and good heat dissipation performance.

In one or more alternative embodiments, the diameter of the cylindrical cells is 17mm-22mm and the height of the cylindrical cells is 64mm-72mm.

In one or more alternative embodiments, the cylindrical cell is a 18650-type cell or a 21700-type cell.

In one or more alternative embodiments, the electrochemical device has a rated capacity of 2500 milliamperes per milliampere hour to 4500 milliampere hours.

In one or more alternative embodiments, the direct current resistance of the electrochemical device is less than or equal to 10 milliohms at the first ambient temperature. The electrochemical device has smaller direct current resistance, and the electrochemical device has lower temperature rise in the discharge process of high multiplying power, thereby being beneficial to reducing energy loss, improving the discharge capacity of the electrochemical device and improving the discharge performance of the electrochemical device.

In a second aspect, the present examples also provide a battery pack including the electrochemical device provided according to any one of the embodiments of the first aspect.

In one or more of the above alternative embodiments, the battery pack includes one battery module or a plurality of battery modules arranged in parallel, and one battery module includes a plurality of electrochemical devices arranged in series.

In a third aspect, embodiments of the present application further provide a powered device, which includes a battery pack provided according to any one of the embodiments of the second aspect.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following description will briefly explain the drawings that are required to be used in the embodiments of the present application.

Fig. 1 is a schematic structural view of an electrochemical device according to some embodiments of the present application;

fig. 2 is an exploded view of the electrochemical device shown in fig. 1;

fig. 3 is a schematic front view of an electrode assembly of an electrochemical device provided in some embodiments of the present application;

FIG. 4 is a schematic top view of the electrode assembly shown in FIG. 3;

FIG. 5 is a schematic cross-sectional view taken along the direction A-A of FIG. 3;

FIG. 6 is a schematic illustration of a first pole piece of an electrochemical device in an expanded state provided in some embodiments of the present application;

FIG. 7 is a schematic cross-sectional view taken along the direction B-B of FIG. 6;

fig. 8 is a schematic partial cross-sectional view of a first flattened area, current collector plate, and insulator of a cell provided in some embodiments of the present application;

fig. 9 is a schematic partial cross-sectional view of a first flattened area and an insulator of a cell provided in some embodiments of the present application;

FIG. 10 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present disclosure in an expanded state;

FIG. 11 is an enlarged schematic view of FIG. 10 at the circle;

FIG. 12 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present application in an expanded state;

FIG. 13 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present application in an expanded state;

FIG. 14 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present disclosure in an expanded state;

FIG. 15 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present application in an expanded state;

FIG. 16 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present application in an expanded state;

FIG. 17 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present disclosure in an expanded state;

FIG. 18 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present application in an expanded state;

FIG. 19 is a schematic view of a first pole piece of an electrochemical device according to further embodiments of the present disclosure in an expanded state;

FIG. 20 is a schematic illustration of a second pole piece of an electrochemical device in an expanded state provided in some embodiments of the present application;

FIG. 21 is a schematic cross-sectional view of FIG. 20 taken along the direction C-C;

FIG. 22 is a schematic view of a battery pack provided in some embodiments of the present application;

FIG. 23 is a schematic diagram of a powered device according to some embodiments of the present application;

FIG. 24 is a schematic view of discharge performance of an electrochemical device according to some embodiments of the present disclosure at different rates;

fig. 25 is a partial schematic view of fig. 24.

The reference numerals are as follows:

Detailed Description

For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more apparent, the technical solutions in the embodiments of the present application will be clearly described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments.

In the description of the present application, it should be noted that, unless explicitly specified and limited otherwise, the terms "mounted," "connected," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the terms in this application will be understood by those of ordinary skill in the art as the case may be.

In the examples of the present application, "parallel" includes not only the case of absolute parallelism but also the case of substantially parallelism as is conventionally recognized in engineering; meanwhile, "vertical" includes not only the case of absolute vertical but also the case of substantially vertical as conventionally recognized in engineering. Illustratively, the angle between the two directions is 85 ° -90 °, which can be considered to be perpendicular; the included angle between the two directions is 0-5 degrees, and the two directions can be considered to be parallel.

Referring to fig. 1 to 9, an electrochemical device 1000 is provided according to an embodiment of the present application. The electrochemical device 1000 may be a secondary cell, which refers to a cell that can be continuously used by activating an active material by means of charging after the cell is discharged.

In some embodiments, the electrochemical device 1000 may be a cylindrical cell, a prismatic cell, or other shaped cell, including square-case cells, blade-shaped cells, polygonal-prismatic cells, such as hexagonal-prismatic cells, and the like.

In some embodiments, the electrochemical device 1000 includes a case 2 and an electrode assembly 1 accommodated within the case 2.

The electrode assembly 1 includes a first electrode tab 11 and a second electrode tab 12 of opposite polarity. One of the first electrode sheet 11 and the second electrode sheet 12 is a positive electrode sheet, and the other is a negative electrode sheet.

During the charge and discharge of the electrochemical device 1000, active ions (e.g., lithium ions) are inserted and extracted back and forth between the positive electrode tab and the negative electrode tab.

Optionally, the electrode assembly 1 further comprises a separator 13 disposed between the first and second electrode sheets 11 and 12, the separator 13 insulating the first and second electrode sheets 11 and 12. The separator 13 can reduce the risk of shorting the positive and negative plates while allowing the passage of active ions.

One or more electrode assemblies 1 may be accommodated in the case 2.

In some embodiments, the electrode assembly 1 may be a wound structure, a laminated structure, or other structures.

In some embodiments, the electrode assembly 1 may have a cylindrical shape, a flat shape, a polygonal column shape, or the like.

In some embodiments, the case 2 is used to encapsulate the electrode assembly 1 and the electrolyte. The shell 2 may be a steel shell, an aluminum shell, a plastic shell (such as polypropylene) or a composite metal shell (such as a copper-aluminum composite shell 2), etc.

In some embodiments, the electrochemical device 1000 further includes a cover plate 5, the case 2 has an opening, and the cover plate 5 is used to cover the opening. The case 2 cooperates with the cap plate 5 to form an internal cavity of the electrochemical device 1000, which may be used to accommodate the electrode assembly 1, electrolyte, and other components.

The housing 2 may be of various shapes and sizes, such as rectangular parallelepiped or cylindrical. The material of the housing 2 may be various, for example, the material of the housing 2 includes, but is not limited to, copper, iron, aluminum, stainless steel, aluminum alloy, and the like.

The cover plate 5 may be welded, glued, snapped or otherwise attached to the housing 2.

In some embodiments, the casing 2 may be an open-sided structure, and the cover plate 5 is disposed as one piece and covers the casing 2. In other embodiments, two cover plates 5 are provided, and the two cover plates 5 cover the two openings of the housing 2 respectively.

In some embodiments, the electrochemical device 1000 further includes an electrode terminal 3, and the electrode terminal 3 is disposed at the cap plate 5.

In some examples, the electrochemical device 1000 includes one electrode terminal 3, one of the electrode terminal 3 and the case 2 is electrically connected to the first electrode tab 11, and the other is electrically connected to the second electrode tab 12. One of the electrode terminal 3 and the case 2 serves as a positive electrode of the electrochemical device 1000, and the other serves as a negative electrode of the electrochemical device 1000.

In other examples, the electrochemical device 1000 includes two electrode terminals 3, and the two electrode terminals 3 are electrically connected to the first and second electrode tabs 11 and 12, respectively. The two electrode terminals 3 are a positive electrode and a negative electrode of the electrochemical device 1000, respectively.

In some embodiments, the electrochemical device 1000 further includes a current collecting tray 4, the current collecting tray 4 connecting the electrode terminal 3 and the electrode assembly 1. The current collecting plate 4 connects the electrode terminal 3 and the first electrode tab 11, for example.

In some embodiments, the first pole piece 11, the diaphragm 13, and the second pole piece 12 are stacked and wound in the winding direction V. The winding direction V may be a direction in which the second pole piece 12, the separator 13, and the first pole piece 11 are wound from inside to outside. Illustratively, as shown in fig. 5, the winding direction V is clockwise.

In some embodiments, the first pole piece 11 includes a first current collector 111 and a first active material 112 disposed on the first current collector 111.

For example, the first current collector 111 may have two surfaces opposite in the thickness direction thereof, and the first active material 112 may be disposed on either or both of the two surfaces opposite to the first current collector 111.

In some embodiments, the first current collector 111 may employ a metal foil, such as a stainless steel foil, a copper foil, an aluminum foil, a nickel foil, or the like.

In some embodiments, the first current collector 111 includes a first body region 111a and a first empty foil region 111b, and the first active material 112 is disposed in the first body region 111a, and the arrangement direction of the first body region 111a and the first empty foil region 111b is perpendicular to the winding direction V.

Illustratively, the arrangement direction of the first body region 111a and the first dummy foil region 111b is parallel to the winding axis direction P of the electrode assembly 1.

At least one surface of the first body region 111a is coated with a first active material 112. Both surfaces of the first empty foil region 111b are not coated with the first active material 112.

A partial region of the first hollow foil region 111b may be provided with other coatings, such as an insulating coating, which do not comprise an active material. Of course, both surfaces of at least part of the area of the first blank foil area 111b are bare, uncovered by other coatings. The exposed area of the first empty foil region 111b may serve as the first tab 10a of the electrode assembly 1, and the first tab 10a may conduct out the current of the electrode assembly 1.

Illustratively, after the first pole piece 11 is unfolded, the arrangement direction of the first body region 111a and the first empty foil region 111b is parallel to the width direction Y of the first pole piece.

In some embodiments, the first empty foil region 111b includes a first flattened region 111c, the first flattened region 111c being remote from the first body region 111a. Illustratively, as shown in fig. 6, a portion of the first blank foil region 111b located on the upper side of the virtual line is used to form the first flattened region 111c.

After the electrode assembly 1 is wound, the first hollow foil region 111b is wound and forms a columnar structure, and an external tool can apply an external force to the first hollow foil region 111b along the circumferential direction of the columnar structure, so that the first hollow foil region 111b is bent and deformed, two layers adjacent to each other in the radial direction of the first hollow foil region 111b are more compact, and a first flattening region 111c is formed.

The first flattened area 111c forms a dense end surface to facilitate connection with other conductive structures, such as soldering with the current collecting plate 4.

In some embodiments, the electrochemical device 1000 is configured to: in response to the electrochemical device 1000 having a 100% SOC performing a discharge operation at a first discharge rate at a first ambient temperature, the discharge operation is continued until the SOC of the electrochemical device 1000 is 0%, and a ratio of a discharge capacity of the electrochemical device 1000 to a rated capacity of the electrochemical device 1000 is greater than or equal to 80%. The first ambient temperature is 22-28 ℃, and the first discharge multiplying power is 15-20 ℃.

In the present embodiment, SOC (State of charge) refers to the state of charge of the electrochemical device.

In the embodiment of the present application, the charge and discharge operation of the electrochemical device 1000 is performed within the allowable number of charge and discharge cycles. The number of charge and discharge cycles allowed is obtained from the manufacturer or seller on a label, package, user manual, instruction, advertisement, marketing or other support file for use by the user.

Illustratively, an electrochemical device at a SOC of 100% may refer to: at 25 ℃, the electrochemical device was discharged to a discharge cutoff voltage of the electrochemical device at a constant current of 0.5C, then charged to a charge cutoff voltage of the electrochemical device at a constant current of 0.5C, and then charged to 0.05C at a constant voltage of the charge cutoff voltage, at which time the electrochemical device was at 100% SOC.

The charge and discharge process of the electrochemical device may be tested by a battery tester (newware CT-4016-5V-100A), for example.

For example, the discharge cut-off voltage and the charge cut-off voltage of the electrochemical device may be obtained from a manufacturer or seller on a label, package, user manual, instruction, advertisement, marketing, or other supporting document of these products for use by a user. The advertising voltage may include a digital voltage value, or other words, phrases, alphanumeric character combinations, icons, or indicia to the user indicating how the electrochemical device is to operate.

The electrochemical device may be a 18650 cell or a 21700 cell, for example. The discharge cut-off voltage of 18650 cells may be 2.5V and the charge cut-off voltage may be 4.2V. The 21700 cell may have a discharge cutoff voltage of 2.5V and a charge cutoff voltage of 4.2V.

For example, when the load of the electrochemical device reaches the rated capacity of the electrochemical device at the initial stage of the cycle, the electrochemical device may be considered to be at 100% SOC.

Illustratively, the rated capacity of an electrochemical device may be considered as: an electrochemical device at 100% SOC was discharged to 0% SOC at 25 ℃ with a constant current at a rate of 0.2C, and the discharged capacity was the rated capacity.

Illustratively, an electrochemical device at a SOC of 0% means: the electrochemical device was discharged constant-current at a certain rate to a discharge cutoff voltage of the electrochemical device, at which time the electrochemical device was at 0% SOC.

For example, the rated capacity of the electrochemical device may be obtained from the manufacturer or seller on a label, package, user manual, instruction, advertisement, marketing, or other support document for use by the user of such products. The rated capacity may include numbers, or other words, phrases, alphanumeric character combinations, icons, or indicia to the user of how the electrochemical device works.

For example, the rated capacity of 18650 cells may be 2500 milliamperes (mAh), 2600 milliamperes (mAh), 2700 milliamperes (mAh), 2800 milliamperes (mAh), 2900 milliamperes (mAh), 3000 milliamperes (mAh), 3100 milliamperes (mAh), 3200 milliamperes (mAh), 3300 milliamperes (mAh), 3400 milliamperes (mAh), 3500 milliamperes (mAh). Illustratively, the rated capacity of the 21700 cell may be 3500 milliamperes (mAh), 3600 milliamperes (mAh), 3700 milliamperes (mAh), 3800 milliamperes (mAh), 3900 milliamperes (mAh), 4000 milliamperes (mAh), 4100 milliamperes (mAh), 4200 milliamperes (mAh), 4300 milliamperes (mAh), 4400 milliamperes (mAh), 4500 milliamperes (mAh).

Illustratively, discharge rate = current/rated capacity. Illustratively, the discharge rate of an electrochemical device or battery pack in terms of its total storage capacity is expressed in Ah or mAh. Illustratively, a magnification of 1C represents the utilization of all stored energy at 1 hour; a magnification of 0.5C means that all stored energy is utilized at 2 hours; the magnification of 10C means that all the stored energy is utilized at 0.1 hours.

For example, the discharge rate is xC, the time for the electrochemical device to discharge from 100% SOC to 0% SOC is t, and t is equal to 1/x hours.

Illustratively, charging rate = current/rated capacity. Illustratively, the charging current is 4000×0.5 milliamps during the charging operation at a 0.5C charging rate when the rated capacity of the electrochemical device is 4000 milliamps.

The discharge capacity of the electrochemical device 1000 can be measured by a battery tester (newware CT-4016-5V-100A). For example, the discharge operation is performed at the first discharge rate, the discharge operation is continued until the SOC of the electrochemical device 1000 is 0%, the duration of the discharge operation is t, the current corresponding to the first discharge rate is i, and the discharge capacity may be t×i.

As an example, the first ambient temperature is a constant temperature. For example, the electrochemical device 1000 may perform an operation in an incubator (Keming EH-1000).

As an example, the first ambient temperature may be 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃, 27 ℃, or 28 ℃.

As an example, the first discharge magnification may be 15C, 16C, 17C, 17.5C, 18C, 19C, or 20C.

According to the embodiment of the application, the overcurrent capacity can be increased by setting the first rubbing zone, the resistance of the electrochemical device is small, the temperature rise of the electrochemical device is low when the discharge is carried out at a high multiplying power of 15C-20C, and the energy loss is reduced, so that the electrochemical device can have higher discharge capacity, more electric energy is provided for electric equipment, and the discharge performance of the electrochemical device is improved.

In some embodiments, the ratio of the discharge capacity of the electrochemical device 1000 to the rated capacity of the electrochemical device 1000 is greater than or equal to 90%. The electrochemical device 1000 can have a higher discharge capacity when discharging at a high rate of 15C-20C, providing more power to the consumer.

In some embodiments, the ratio of the discharge capacity of the electrochemical device 1000 to the rated capacity of the electrochemical device 1000 is greater than or equal to 95%. The electrochemical device 1000 can have a higher discharge capacity when discharging at a high rate of 15C-20C, providing more power to the consumer.

In some embodiments, the ratio of the discharge capacity of the electrochemical device 1000 to the rated capacity of the electrochemical device 1000 is greater than or equal to 98%. The electrochemical device 1000 can have a higher discharge capacity when discharging at a high rate of 15C-20C, providing more power to the consumer.

In some embodiments, the first discharge rate is in the range of 17.5C-20C. When the discharge is performed at a high rate of 17.5C-20C, the ratio of the discharge capacity of the electrochemical device 1000 to the rated capacity of the electrochemical device 1000 is greater than or equal to 99%, so that more electric energy can be provided for electric equipment.

In some embodiments, the first ambient temperature is 25 ℃.

In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material disposed on the positive electrode current collector, the positive electrode active material including Li _1+a Ni _x1 Co _y1 Mn _z1 O ₂ Or Li (lithium) _1+a Ni _x2 Co _y2 Al _z2 O ₂ At least one of them. Wherein x1 and x2 are both greater than or equal to 0.8, y1 and y2 are both greater than 0, z2 and z3 are both greater than 0, x1+y1+z1=1, x2+y2+z2=1, -0.05.ltoreq.a.ltoreq.0.2.

In some embodiments, x1 and x2 are both greater than or equal to 0.9.

In some embodiments, the positive electrode active material includes LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 、LiNi _0.91 Co _0.04 Mn _0.05 O ₂ 、LiNi _0.92 Co _0.03 Mn _0.05 O ₂ 、LiNi _0.93 Co _0.02 Mn _0.05 O ₂ 、LiNi _0.94 Co _0.01 Mn _0.05 O ₂ 、LiNi _0.95 Co _0.01 Mn _0.04 O ₂ 、LiNi _0.8 Co _0.1 Al _0.1 O ₂ 、LiNi _0.91 Co _0.04 Al _0.05 O ₂ 、LiNi _0.92 Co _0.03 Al _0.05 O ₂ 、LiNi _0.93 Co _0.02 Al _0.05 O ₂ 、LiNi _0.94 Co _0.01 Al _0.05 O ₂ 、LiNi _0.95 Co _0.01 Al _0.04 O ₂ At least one of them.

In some embodiments, the positive electrode active material includes a positive electrode active material including Li, a binder, and a conductive agent _1+a Ni _x1 Co _y1 Mn _z1 O ₂ Or Li (lithium) _1+a Ni _x2 Co _y2 Al _z2 O ₂ At least one of them.

In some embodiments, the adhesive comprises at least one of polyacrylic acid (PAA), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), or Polyamide (PA).

In some embodiments, the conductive agent includes at least one of acetylene black, conductive carbon black, carbon nanotubes, carbon fibers, crystalline flake graphite, ketjen black, or graphene.

In some embodiments, in the positive electrode active material, the mass percentage of the positive electrode active material is 90% -98%, the mass percentage of the binder is 1.25% -5%, and the mass percentage of the conductive agent is 0.75% -5%.

In some embodiments, the negative electrode tab includes a negative electrode current collector and a negative electrode active material disposed on the negative electrode current collector, the negative electrode active material including artificial graphite and/or natural graphite.

In some embodiments, a binder and a conductive agent are also included in the anode active material.

In some embodiments, the first electrode sheet 11 is a positive electrode sheet, the first current collector 111 is a positive electrode current collector, and the first active material 112 is a positive electrode active material. In other embodiments, the first electrode sheet 11 is a negative electrode sheet, the first current collector 111 is a negative electrode current collector, and the first active material 112 is a negative electrode active material.

In some embodiments, the electrochemical device 1000 further includes an electrolyte contained within the housing 2. The electrolyte comprises lithium hexafluorophosphate (LiPF) ₆ ) And fluoroethylene carbonate (FEC), the mass percentage of lithium hexafluorophosphate is 12-16% based on the mass of the electrolyte, and the mass percentage of fluoroethylene carbonate is 0.8-1.5%.

The electrolyte also includes a solvent. Illustratively, the solvent of the electrolyte is a mixed solvent of Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) (EC: EMC mass ratio=70:30). The solute is lithium hexafluorophosphate (LiPF) ₆ ) The additive is fluoroethylene carbonate (FEC). Optionally, based on the mass of the electrolyte, liPF ₆ 15% by mass and 1% by mass of FEC.

FEC is used as electrolyte additive, which is beneficial to improving the performance of SEI film, forming a compact structure layer without increasing impedance, preventing electrolyte from further decomposition and improving the discharge performance of electrochemical device.

In some embodiments, the electrochemical device 1000 is a cylindrical cell. The cylindrical battery cell has mature production process, higher product yield and good heat dissipation performance.

In some embodiments, the diameter of the cylindrical cells is 17mm-22mm. Alternatively, the diameter of the cylindrical cell is 17mm, 18mm, 19mm, 20mm, 21mm or 22mm.

In some embodiments, the height of the cylindrical cells is 64mm-72mm. Alternatively, the height of the cylindrical cells is 64mm, 65mm, 66mm, 67mm, 68mm, 69mm, 70mm, 71mm or 72mm.

In some embodiments, the electrochemical device 1000 is a 18650-type cell or a 21700-type cell.

In some embodiments, the rated capacity of the electrochemical device 1000 is 2500 milliamperes (mAh) to 4500 milliamperes (mAh). Alternatively, the electrochemical device has a rated capacity of 2500 milliamperes (mAh), 2600 milliamperes (mAh), 2700 milliamperes (mAh), 2800 milliamperes (mAh), 2900 milliamperes (mAh), 3000 milliamperes (mAh), 3100 milliamperes (mAh), 3200 milliamperes (mAh), 3300 milliamperes (mAh), 3400 milliamperes (mAh), 3500 milliamperes (mAh), 3600 milliamperes (mAh), 3700 milliamperes (mAh), 3800 milliamperes (mAh), 3900 milliamperes (mAh), 4000 milliamperes (mAh), 4100 milliamperes (mAh), 4200 milliamperes (mAh), 4300 milliamperes (mAh), 4400 milliamperes (mAh), or 4500 milliamperes (mAh).

In some embodiments, the direct current resistance of the electrochemical device 1000 is less than or equal to 10 milliohms at the first ambient temperature.

The dc resistance of the electrochemical device 1000 is illustratively tested as follows:

at 25 ℃, the electrochemical device is discharged to a discharge cut-off voltage of the electrochemical device at a constant current of 0.5C, then is charged to a charge cut-off voltage of the electrochemical device at a constant current of 0.5C, and then is charged to 0.05C at a constant voltage of the charge cut-off voltage, at which time the electrochemical device is at 100% SOC;

Standing for 2 hours at a first ambient temperature;

discharging for 10s at a current i1 corresponding to a 0.1C multiplying power at a first ambient temperature, and measuring a voltage V1; then discharging for 1s with a current i2 corresponding to the 1C multiplying power, and measuring a voltage V2;

the direct current resistance of the electrochemical device was (V1-V2)/(i 2-i 1).

The electrochemical device 1000 has smaller direct current resistance, the electrochemical device 1000 has lower temperature rise in the discharge process of high multiplying power, the energy loss is reduced, the discharge capacity of the electrochemical device is improved, and the discharge performance of the electrochemical device is improved.

In some embodiments, along the width direction Y of the first pole piece 11 after being unfolded, the first empty foil region 111b has a size W1, and the total size of the first current collector 111 is W2, W1 and W2 satisfy: W1/W2 is more than or equal to 0.05 and less than or equal to 0.1.

By defining W1/W2 to be greater than or equal to 0.05, the first blank foil region 111b may be made to have a larger width, facilitating connection of the first blank foil region 111b to other conductive structures. Limiting W1/W2 to less than or equal to 0.1 allows more space for the first active material 112, reducing energy density losses.

In addition, when the first empty foil area 111b is flattened, the first empty foil area 111b is deformed by bending; in the embodiment of the application, the W1/W2 is larger than or equal to 0.05, so that the stress of the first active substance 112 is reduced during rubbing, and the risks of deformation and powder falling of the first active substance 112 are reduced.

Alternatively, W1/W2 may be 0.05, 0.06, 0.07, 0.08, 0.09, or 0.1.

In some embodiments, the first flattened area 111c has a dimension W4, 0.6.ltoreq.W4/W1.ltoreq.0.95 along the width direction Y of the expanded first pole piece 11.

Limiting W4/W1 to 0.6 or more increases the compression area of the first hollow foil region 111b during flattening, reduces the axial dimension of the electrode assembly 1, improves space utilization and makes the first flattening region 111c denser. Defining W4/W1 to be less than or equal to 0.95 may reduce the force transferred to the first active 112 during the flattening process, reducing the risk of the first active 112 falling off.

Alternatively, W4/W1 is 0.6, 0.7, 0.8, 0.9 or 0.95.

In some embodiments, the first hollow foil region 111b has a dimension L1 and the first body region 111a has a dimension L2 along the length direction X of the first pole piece 11 after being unfolded. L1 and L2 satisfy: L1/L2 is more than or equal to 0.8 and less than or equal to 1.

Along the length direction X, L1 of the first pole piece 11 after being stretched is the maximum size of the first hollow foil region 111b after being stretched.

Illustratively, the first pole piece 11 may be unfolded to a flat sheet-like structure, and correspondingly, the first flattening area 111c is flattened.

The first empty foil region 111b has a larger overcurrent area, and when the electrochemical device 1000 is discharged at a high rate, the first empty foil region 111b can pass a larger current, thereby reducing heat generation of the first empty foil region 111b and reducing the risk of fusing of the first empty foil region 111 b.

Alternatively, L1/L2 may be 0.8, 0.85, 0.9, 0.95, or 1.

In some embodiments, 0.9 is less than or equal to L1/L2 is less than or equal to 0.95, so that the overcurrent capacity of the first empty foil region 111b can be further improved, the size of the first empty foil region 111b is reduced on the premise that the first empty foil region 111b meets the overcurrent capacity, the occupied space and weight of the first empty foil region 111b are reduced, the energy density is improved, and the electrolyte infiltration is facilitated.

In some embodiments, the first empty foil region 111b is disposed continuously along the winding direction V and wound in a plurality of turns. The first empty foil region 111b is continuously wound, so that the overall strength of the first empty foil region 111b can be increased; the first hollow foil region 111b is entirely continuous, and current can be transmitted in different regions of the first hollow foil region 111b, and current uniformity of the first pole piece 11 is improved.

In some embodiments, the electrochemical device 1000 further includes an electrode terminal 3 provided to the case 2 and a current collecting plate 4 connecting the first flattening region 111c and the electrode terminal 3.

The first flattening area 111c has a dense end surface, and the connection strength can be improved by connecting the first flattening area 111c to the current collecting plate 4.

In some embodiments, the manifold disk 4 is welded to the first flattened area 111c. The embodiment of the application can reduce the risk of cold joint, improve the welding strength, reduce the risk of burning the diaphragm 13 due to laser leakage and improve the safety.

In some embodiments, the collecting tray 4 is provided with through holes 41. In the liquid injection process, the electrolyte may pass through the through-hole 41 and infiltrate the electrode assembly 1, improving wettability. When the electrochemical device 1000 fails due to overheating, overcharge, short-circuiting, or other reasons, the electrode assembly 1 may release gas; by providing the through-holes 41, a passage can be provided for the gas, thereby rapidly discharging the gas to the outside of the electrochemical device, and reducing the risk of explosion.

In some embodiments, the electrochemical device 1000 further includes an insulating member 6, and the insulating member 6 surrounds the outside of the first flattening region 111c.

The insulating sheet 6 may separate the first flattened area 111c from the housing 2 to reduce the risk of short circuits. The insulating sheet 6 can also gather the first flattened region 111c from the outer periphery, reducing the risk of the first flattened region 111c spreading out.

In some embodiments, the insulator 6 surrounds at least one revolution of the first flattened area 111c.

In some embodiments, an overlap region 61 is provided at the surrounding interface of the insulator 6. The insulating elements 61 may be connected in the overlapping region 61 to reduce the risk of the insulating element 6 falling off the first flattened area 111c.

In some embodiments, the insulator 6 is bonded at the overlap region 61.

In some embodiments, the insulation 6 comprises tape.

In some embodiments, the overlap region 61 avoids the outer end of the first flattened region 111c in the winding direction V. Illustratively, in the radial direction of the first flattened region 111c, the outer end of the first flattened region 111c in the winding direction does not overlap the overlapping region 61, alleviating the problem that an increase in thickness after overlapping results in an increase in size in the radial direction to reduce energy density.

In connecting the insulating member 6, it is necessary to press the overlap region 61 from the outside. The overlapping region 61 avoids the outer end of the first rubbing region 111c, which is beneficial to reducing the problems of lithium precipitation caused by extrusion of the outer end of the first rubbing region 111c when the electrochemical device expands.

Referring to fig. 10 and 11, in some embodiments, a corner of the outer end of the first empty foil region 111b in the winding direction V is provided with a first cutout G1.

Illustratively, the first cutout G1 is located at one end of the first blank foil area 111b along the length direction X of the first pole piece 11 after being unfolded.

After the first blank foil area 111b is formed into the first flattened area 111c by flattening, the insulator 6 may be attached to the outside Zhou Tie of the first flattened area 111 c; by providing the first slit G1, the risk of piercing the insulating member 6 due to an excessively large sharp angle at the outer end of the first hollow foil region 111b can be reduced, which is advantageous for reducing the usage amount of the insulating member 6 and improving the energy density.

In some embodiments, the first blank foil section 111b is provided with a second cut G2 at the corner of the inner end in the winding direction V.

Illustratively, the first and second slits G1 and G2 are located at both ends of the first hollow foil region 111b in the length direction X of the first pole piece 11 after being unfolded.

In some embodiments, the first incision G1 is sized La along the length direction X of the first pole piece 11 after deployment; la and W1 satisfy: la/W1 is more than or equal to 0.2 and less than or equal to 4.

The La/W1 is limited to be greater than or equal to 0.2, so that the accumulation of the empty foil material can be reduced in the flattening process, the risk of puncturing the insulating member coating the first empty foil region 111b is reduced, and the safety is improved. Limiting La/W1 to 4 or less can reduce the influence of the first notch G1 on the overcurrent capability of the first blank foil region 111 b.

Alternatively, la/W1 is 0.2, 0.3, 0.5, 0.8, 1.0, 1.5, 1.8, 2, 2.5, 3, 3.5 or 4.

In some embodiments, 0.5.ltoreq.La/W1.ltoreq.2.

In some embodiments, the first incision G1 has a dimension W3 along the width direction Y of the first pole piece 11 after being unfolded; w3 and W1 satisfy: W3/W1 is more than or equal to 0.2 and less than or equal to 1.

The W3/W1 is defined to be greater than or equal to 0.2, so that accumulation of empty foil materials can be reduced in the rolling process, the risk of puncturing an insulating member coating the first empty foil region 111b is reduced, and safety is improved. Defining W3/W1 to be less than or equal to 1 may reduce the risk of the first incision G1 opening into the first body region 111a, reducing the loss of the first active material 112.

Alternatively, W3/W1 is 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 1.

In some embodiments, the first and second cuts G1, G2 are both the same in shape and size.

In some embodiments, the first notch G1 may be formed by chamfering corners of the first blank foil area 111 b.

In some embodiments, the first notch G1 may be a triangular notch. Illustratively, the triangular cut may be formed by chamfering the first blank foil area 111 b.

Referring to fig. 12, in some embodiments, the first incision G1 may be an arc incision. Illustratively, the arcuate cuts may be formed by rounding off the first blank foil region 111 b.

Referring to fig. 13, in some embodiments, the first cutout G1 may be a rectangular cutout.

In some embodiments, referring to fig. 14, the first empty foil region 111b includes a plurality of first sub-tabs 1111, and the plurality of first sub-tabs 1111 are separately disposed along the length direction X of the first pole piece 11 after being unfolded.

The plurality of first sub-tabs 1111 are separated and arranged, so that each first sub-tab 1111 is easier to bend and deform in the rubbing process, and the stress in the rubbing process is reduced.

The plurality of first sub-tabs 1111 are discontinuous in the winding direction V, and adjacent first sub-tabs 1111 may or may not be in contact in the winding direction V.

In some embodiments, the minimum distance D between adjacent first sub-tabs 1111 along the length direction X of the expanded first pole piece 11 is 0mm to 66mm.

Alternatively, D may be 0mm, 1mm, 5mm, 8mm, 10mm, 20mm, 30mm, 40mm, 50mm, 60mm or 66mm.

In the embodiment of the application, the D is limited to 0mm-66mm, so that the electrolyte can be infiltrated easily under the condition of separating the adjacent first sub-tabs 1111, and the loss of the overcurrent area of the first empty foil region 111b is reduced.

In some embodiments, along the length direction X of the first pole piece 11 after being unfolded, the sum of the dimensions of the plurality of first sub-tabs 1111 is L3, and the dimensions of the first body region 111a are L2, L3 and L2 satisfy: L3/L2 is more than or equal to 0.8 and less than or equal to 1.

In some embodiments, the length direction X, L3 along which the first pole piece 11 is unfolded is the sum of the minimum dimensions of the plurality of first sub-tabs 1111.

For example, the minimum dimensions of the n first sub-tabs 1111 along the length direction X of the first pole piece after being unfolded are K1, K2, … …, kn, n is a positive integer greater than 1, l3=k1+k2+ … … +kn, respectively. For example, as shown in fig. 14, the first sub-tabs 1111 are four, and l3=k1+k2+k3+k4.

The plurality of first sub-tabs 1111 have a larger overcurrent area, so that heat generation of the first sub-tabs 1111 and the risk of fusing of the first sub-tabs 1111 can be reduced when the electrochemical device 1000 is discharged at a high rate.

Alternatively, L3/L2 may be 0.8, 0.85, 0.9, 0.95, or 1.

In some embodiments, 0.9.ltoreq.L3/L2.ltoreq.0.95.

According to the embodiment of the application, the overcurrent capacity of the first sub-tabs 1111 can be increased, more gaps are reserved between the adjacent first sub-tabs 1111, the resistance of the first sub-tabs 1111 in the rubbing process is reduced, and the electrolyte infiltration is facilitated.

In some embodiments, the number of first sub-tabs 1111 is greater than or equal to 4. The number of first sub-tabs 1111 is, for example, 4, 5, 6, 8, 10, 12, 15, 18, or 20.

On the premise that the sum L3 of the plurality of first sub-tabs 1111 is constant, the number of the first sub-tabs 1111 is increased, so that the rubbing resistance of the single first sub-tab 1111 is reduced.

In some embodiments, a plurality of first sub-tabs 1111 are disposed at equal intervals along the length direction X of the first pole piece 11 after being unfolded.

In some embodiments, the plurality of first sub-tabs 1111 are the same size along the length direction X of the first pole piece 11 after being unfolded.

In some embodiments, the first empty foil region 111b further includes a transition portion (not shown) that is continuously disposed along the winding direction V and connects the first body region 111a and the plurality of first sub-tabs 1111.

In some embodiments, the transition is equal in size to the first body region 111a along the length direction X of the first pole piece 11 after deployment.

Referring to fig. 16, in some embodiments, along the length direction X of the first pole piece 11 after being unfolded, the inner end E1 of the first empty foil region 111b and the inner end E3 of the first body region 111a are spaced apart by a first distance D1, and the first body region 111a has a dimension L2. D1/L2 is more than 0 and less than 0.2.

After the electrode assembly 1 is wound and formed, a central hole 10c is formed in the middle. The center hole 10c may serve as a liquid injection passage at the time of liquid injection. In the embodiment of the application, the D1/L2 is set to be greater than 0, so that the distance between the first empty foil area 111b and the central hole 10c can be increased, and the risk that the first empty foil area 111b shields the central hole 10c in the rubbing process is reduced.

In the embodiment, the D1/L2 is set to be less than 0.2, so that the loss of the overcurrent capability of the first empty foil region 111b can be reduced, and the electrochemical device 1000 can discharge at a high rate.

In some embodiments, D1/L2 may be 0.05, 0.1, 0.15, or 0.18.

In some embodiments, 0.05.ltoreq.D1/L2.ltoreq.0.1 may reduce resistance to flattening the first empty foil region 111b, improve wettability of the electrolyte, and reduce loss of overcurrent capability of the first empty foil region 111b, enabling the electrochemical device 1000 to discharge at a large rate.

Referring to fig. 16, in some embodiments, along the length direction X of the first pole piece 11 after being unfolded, the outer end E2 of the first empty foil region 111b and the outer end E4 of the first body region 111a are spaced apart by a second distance D2, and the first body region 111a has a size L2,0 < D2/L2 < 0.2.

According to the embodiment of the application, the D2/L2 is set to be larger than 0, so that the outer diameter of the columnar structure formed by winding the first empty foil region 111b can be reduced, and the first empty foil region 111b can be flattened from the outside by using an external tool. In the embodiment, the D2/L2 is set to be less than 0.2, so that the loss of the overcurrent capability of the first empty foil region 111b can be reduced, and the electrochemical device 1000 can discharge at a high rate.

In some embodiments, D2/L2 may be 0.05, 0.1, 0.15, or 0.18.

In some embodiments, 0.05.ltoreq.D2/L2.ltoreq.0.1 may reduce resistance to flattening the first empty foil region 111b, improve wettability of the electrolyte, and reduce loss of overcurrent capability of the first empty foil region 111b, enabling the electrochemical device 1000 to discharge at a large rate.

In some embodiments, referring to fig. 17, along the length direction X of the first pole piece 11 after being unfolded, the inner end E1 of the first empty foil region 111b and the inner end E3 of the first body region 111a are spaced apart by a first distance D1, and the outer end E2 of the first empty foil region 111b and the outer end E4 of the first body region 111a are spaced apart by a second distance D2.0 < (D1+D2)/L2 < 0.2, D1 > 0, D2 > 0.

Alternatively, 0.05.ltoreq.D1+D2)/L2.ltoreq.0.1.

Referring to fig. 2 and 18, in some embodiments, the first empty foil region 111b includes a first tab region Z1, a second tab region Z2, and a third tab region Z3 arranged along the length direction X of the first pole piece 11 after being unfolded, each of the first tab region Z1, the second tab region Z2, and the third tab region Z3 including at least two first sub-tabs 1111.

Illustratively, the first tab region Z1 is proximate the inner end E3 of the first body region 111a and the third tab region Z3 is proximate the outer end E4 of the first body region 111 a.

In some embodiments, along the length direction X of the first pole piece 11 after being unfolded, the minimum spacing between adjacent first sub-tabs 1111 of the first tab zone Z1 is d1, the minimum spacing between adjacent first sub-tabs 1111 of the second tab zone Z2 is d2, and the minimum spacing between adjacent first sub-tabs 1111 of the third tab zone Z3 is d3, where d1, d2, and d3 satisfy: d2 < d1, d2 < d3. The electrochemical device 1000 further includes a current collecting plate 4 accommodated in the case 2, and the current collecting plate 4 is welded to the second tab region Z2.

Illustratively, along the length direction X of the first pole piece 11 after being unfolded, the minimum distance between the first sub-tab 1111 of the first tab zone Z1 and the first sub-tab 1111 of the second tab zone Z2 may be flexibly set as required, for example, may be d1.

Illustratively, along the length direction X of the first pole piece 11 after being unfolded, the minimum distance between the first sub-tab 1111 of the third tab zone Z3 and the first sub-tab 1111 of the second tab zone Z2 may be flexibly set as required, for example, may be d3.

The spacing between adjacent first sub-tabs 1111 of the second tab zone Z2 is smaller, after the first empty foil zone 111b is flattened, the second tab zone Z2 is denser, the welding strength of the second tab zone Z2 and the current collecting plate 4 is higher, and the risk of occurrence of cold joint is lower. The first tab zone Z1 and the third tab zone Z3 do not need to be welded with the current collecting plate 4, a larger gap can be formed between the first sub-tabs 1111 of the first tab zone Z1, and a larger gap can be formed between the first sub-tabs 1111 of the third tab zone Z3, so that electrolyte can infiltrate the electrode assembly 1.

In some embodiments, d1.ltoreq.d3. The third tab zone Z3 is closer to the outer ring, the first empty foil zone 111b of the outer ring has a larger circumference, and a larger gap may be provided between the first sub-tabs 1111 of the third tab zone Z3.

In some embodiments, d2 is 0mm-20mm. Alternatively, d2 is 0mm, 3mm, 5mm, 10mm, 15mm or 20mm.

In some embodiments, the dimension of the second tab zone Z2 along the length direction X of the first pole piece 11 after being unfolded is 0.6m-1.1m, i.e. the sum of the dimensions of the plurality of first sub-tabs 1111 of the second tab zone Z2 is 0.6m-1.1m.

The embodiment of the application can increase the overflow area and the connection strength of the second lug zone Z2 and the current collecting disc 4.

In some embodiments, referring to fig. 19, the first empty foil region 111b includes a first tab region Z1, a second tab region Z2, and a third tab region Z3 arranged along the length direction X of the first pole piece 11 after being unfolded, each of the first tab region Z1 and the third tab region Z3 including at least two first sub-tabs 1111, the second tab region Z2 including one first sub-tab 1111. Along the length direction X of the first pole piece 11 after being unfolded, the size of the first sub-tab 1111 of the second tab zone Z2 is larger than the size of the first sub-tab 1111 of the first tab zone Z1, and the size of the first sub-tab 1111 of the second tab zone Z2 is larger than the size of the first sub-tab 1111 of the third tab zone Z3. The electrochemical device 1000 further includes a current collecting plate 4 accommodated in the case 2, and the current collecting plate 4 is welded to the second tab region Z2.

The first sub-tab 1111 of the second tab zone Z2 is continuously disposed and has a larger size, after the first empty foil zone 111b is kneaded, the second tab zone Z2 is more compact, the welding strength of the second tab zone Z2 and the current collecting plate 4 is higher, and the risk of occurrence of cold joint is lower. The first tab zone Z1 and the third tab zone Z3 do not need to be welded with the current collecting plate 4, a larger gap can be formed between the first sub-tabs 1111 of the first tab zone Z1, and a larger gap can be formed between the first sub-tabs 1111 of the third tab zone Z3, so that electrolyte can infiltrate the electrode assembly conveniently.

In some embodiments, the dimension Kz of the first sub-tab 1111 of the second tab zone Z2 is 0.6m-1.1m along the length direction X of the first pole piece 11 after being unfolded. Alternatively, kz is 0.6m, 0.7m, 0.8m, 0.9m, 1.0m or 1.1m.

Illustratively, kz may be the smallest dimension of the first sub-tab 1111 of the second tab zone Z2 along the length direction X of the first pole piece after deployment.

In some embodiments, the dimension Kz of the first sub-tab 1111 of the second tab zone Z2 is greater than the sum of the dimensions of the plurality of first sub-tabs 1111 of the first tab zone Z1.

In some embodiments, the dimension Kz of the first sub-tab 1111 of the second tab zone Z2 is greater than the sum of the dimensions of the plurality of first sub-tabs 1111 of the third tab zone Z3.

Referring to fig. 20 and 21, in some embodiments, the second electrode sheet 12 includes a second current collector 121 and a second active material 122 disposed on the second current collector 121.

For example, the second current collector 121 may have two surfaces opposite in the thickness direction thereof, and the second active material 122 may be disposed on either or both of the two surfaces opposite to the second current collector 121.

In some embodiments, the second current collector 121 may employ a metal foil, such as a stainless steel foil, a copper foil, an aluminum foil, a nickel foil, or the like.

In some embodiments, the second current collector 121 includes a second body region 121a and a second empty foil region 121b, and the second active material 122 is disposed in the second body region 121a. The arrangement direction of the second body region 121a and the second empty foil region 121b is perpendicular to the winding direction V.

At least one surface of the second body region 121a is coated with a second active material 122. Both surfaces of the second empty foil region 121b are not coated with the second active substance 122.

A partial region of the second empty foil region 121b may be provided with other coatings not including an active material, such as an insulating coating. Of course, both surfaces of at least part of the area of the second blank foil area 121b are bare, uncovered by other coatings. The exposed area of the second empty foil region 121b may serve as a second tab 10b of the electrode assembly 1, and the second tab 10b may conduct the current of the electrode assembly 1.

Illustratively, the second body region 121a and the second blank foil region 121b are arranged in a direction parallel to the width direction Y' of the second pole piece 12 after being unfolded.

In some embodiments, the portion of the second hollow foil region 121b remote from the second body region 121a forms a second flattened region by flattening.

After the electrode assembly 1 is wound, the second hollow foil region 121b is wound and forms a columnar structure, and the external fixture can apply external force to the second hollow foil region 121b along the circumferential direction of the columnar structure, so that the second hollow foil region 121b is bent and deformed, two layers adjacent to each other in the radial direction of the second hollow foil region 121b are more compact, and a second flattening region is formed.

The second flattened area forms a dense end surface to facilitate connection with other conductive structures, such as welding with the current collecting plate 4 or housing 2.

In some embodiments, the second electrode sheet 12 is a negative electrode sheet, and correspondingly, the second current collector 121 is a negative electrode current collector, and the second active material 122 is a negative electrode active material.

Referring to fig. 22, the present application also provides a battery pack 3000 including the electrochemical device 1000 provided by any one of the foregoing embodiments.

In some embodiments, the battery pack 3000 includes one battery module 2000 or a plurality of battery modules 2000 arranged in parallel, and one battery module 2000 includes a plurality of electrochemical devices 1000 arranged in series.

The plurality of electrochemical devices 1000 are connected in series, and the output voltage of the battery pack can be increased.

For example, the number of battery modules 2000 of the battery pack 3000 may be 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10.

One battery module 2000 may include 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 electrochemical devices 1000.

In some embodiments, one battery module 2000 includes 5 electrochemical devices 1000 or 6 electrochemical devices 1000.

In some embodiments, the number of battery modules 2000 is 2 or 3.

In some embodiments, the battery pack further includes a case 2100, and the battery module 2000 is accommodated in the case 2100.

Referring to fig. 23, the present application further provides a powered device 4000, which includes a battery pack 3000 provided in any of the foregoing embodiments. Battery pack 3000 may provide power for operation of powered device 4000.

The electric device 4000 of the embodiment of the application may be a portable device, a notebook computer, an electric toy, an unmanned aerial vehicle, an electric tool, an energy storage system, or the like. Power tools include metal cutting power tools, cleaning tools, and the like, such as electric drills, electric wrenches, dust collectors, sweeping robots, and the like. The embodiment of the application does not limit the electric equipment in particular.

In some embodiments, embodiments of the present application provide an electrochemical device including a case and an electrode assembly received within the case.

The electrode assembly comprises a positive electrode plate, a negative electrode plate and a diaphragm, wherein the diaphragm insulates the positive electrode plate and the negative electrode plate.

Example 1

Fabrication of electrochemical device。

< production of Positive electrode sheet >

Lithium nickel cobalt manganese nickel 91 (LiNi _0.91 Co _0.04 Mn _0.05 O ₂ ) Polyvinylidene fluoride (PVDF, weight average molecular weight 7X 10) ⁶ ) Mixing conductive carbon black according to the mass ratio of 95.8:2.8:1.4, adding N-methyl pyrrolidone (NMP) as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the anode slurry with the solid content of 75wt% and uniform system. Uniformly coating the positive electrode slurry on one surface of a positive electrode current collector aluminum foil with the thickness of 13 mu m, and drying at 90 ℃ to obtain a positive electrode plate with single-side coated positive electrode active material (the coating weight of the positive electrode active material on one side of the positive electrode plate is 217mg/1540.25mm per unit area) ² ). And repeating the steps on the other surface of the aluminum foil to obtain the positive electrode plate with the double-sided coating of the positive electrode active material. And then cold pressing and cutting to obtain the positive pole piece for standby.

Illustratively, referring to fig. 6 and 7, the positive electrode tab adopts a similar structure to the first tab. Specifically, l1=l2=1.36 m. W2 was 63.2mm, W1 was 4mm, and W4 was 3.2mm.

< preparation of negative electrode sheet >

Artificial graphite, conductive carbon black, styrene butadiene rubber (SBR, weight average molecular weight of 5×10) ⁶ ) Mixing according to the mass ratio of 97.4:1.4:1.2, adding deionized water as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the anode slurry with the solid content of 51wt% and uniform system. Uniformly coating the anode slurry on one surface of an anode current collector copper foil with the thickness of 8 mu m, and drying at 90 ℃ to obtain an anode sheet with an anode active material layer coated on one side (the coating weight of the anode active material on one side of the anode sheet is 113mg/1540.25mm per unit area) ² ). And repeating the steps on the other surface of the copper foil to obtain the negative electrode plate with the double-sided coating negative electrode active material layer. And cold pressing and cutting to obtain the negative electrode plate for standby.

Illustratively, referring to fig. 6 and 7, the negative electrode tab adopts a similar structure to the first tab. Specifically, l1=l2=1.464 m. W2 is 64.1mm, W1 is 4mm, and W4 is 3.2mm.

< preparation of separator >

An alumina coating layer was provided on one surface of the base film to prepare a separator. Wherein, the base film is a polyethylene film with the thickness of 9 mu m, and the thickness of the alumina coating is 2 mu m.

< preparation of electrolyte >

Mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) according to a mass ratio of 70:30 under an environment with a water content of less than 10ppm to obtain a non-aqueous organic solvent, and adding lithium hexafluorophosphate (LiPF ₆ ) And an additive fluoroethylene carbonate (FEC) are dissolved and uniformly mixed to obtain an electrolyte. Wherein based on the mass of the electrolyte, liPF ₆ 15% by mass, 1% by mass of fluoroethylene carbonate and the balance of non-aqueous organic solvent.

< preparation of electrochemical device >

And stacking and winding the prepared negative electrode plate, the prepared diaphragm and the prepared positive electrode plate in sequence to obtain the electrode assembly with the winding structure. The electrode assembly is arranged in an aluminum shell, and an electrochemical device is obtained through the technological processes of roll edge, liquid injection, formation, degassing, shaping and the like, wherein the electrochemical device is a 21700 lithium ion battery cell with the diameter of 21 mm. The formation process comprises the following steps: the electrochemical device was charged to 3.3V at a constant current of 0.02C and then to 3.6V at a constant current of 0.1C at 25 ℃.

An electrochemical device was prepared according to the above method.

Electrochemical device testing method

The electrochemical device was tested according to the following procedure using a battery tester (newware CT-4016-5V-100A).

First, the electrochemical device was charged to 100% SOC by standing in a 25℃incubator (Keming EH-1000) for 2 hours. Specifically, at a constant temperature of 25 ℃, an electrochemical device was discharged to a discharge cutoff voltage (2.5V) of the electrochemical device at a constant current of 0.5C, then charged to a charge cutoff voltage (4.2V) of the electrochemical device at a constant current of 0.5C, and then charged to 0.05C at a constant voltage of the charge cutoff voltage, at which time the electrochemical device was at 100% SOC.

And (II) standing for 2 hours in a 25 ℃ incubator (Koming EH-1000), discharging the electrochemical device at 100% SOC to a discharge cut-off voltage (2.5V) of the electrochemical device at a constant current of 0.2C, testing discharge capacity, namely rated capacity of the electrochemical device, charging the electrochemical device to a charge cut-off voltage (4.2V) of the electrochemical device at a constant current of 0.5C, and then charging the electrochemical device to 0.05C at a constant voltage of the charge cut-off voltage, wherein the electrochemical device is at 100% SOC.

(III) placing the electrochemical device at 100% SOC in a 25 ℃ incubator (Koming EH-1000) for 2 hours, then discharging at the temperature for 10s at a current i1 corresponding to a 0.1C rate, and measuring a voltage V1; then discharging for 1s with a current i2 corresponding to the 1C multiplying power, and measuring a voltage V2; the direct current resistance of the electrochemical device was (V1-V2)/(i 2-i 1).

(IV) the electrochemical device with the DC resistance tested is placed in an incubator (Koming EH-1000) at 25 ℃ for 2 hours, then discharged to the discharge cut-off voltage (2.5V) of the electrochemical device at a constant current of 0.5C, then charged to the charge cut-off voltage (4.2V) of the electrochemical device at a constant current of 0.5C, and then charged to 0.05C at a constant voltage of the charge cut-off voltage, and the electrochemical device is at 100% SOC.

(V) the electrochemical device at 100% SOC was allowed to stand in a incubator (Koming EH-1000) at 25℃for 2 hours. Then, the temperature in the incubator was maintained, and the electrochemical device was discharged at a discharge rate of 5C until the electrochemical device was discharged to a discharge cutoff voltage (2.5V). During the discharge, the discharge parameters of the electrochemical device were recorded.

And (six) standing the electrochemical device finished in the step (five) in a constant temperature oven (Koming EH-1000) at 25 ℃ for 2 hours, then charging the electrochemical device to a charge cut-off voltage (4.2V) at a constant current of 0.5C, and then charging the electrochemical device to 0.05C at a constant voltage of the charge cut-off voltage, wherein the electrochemical device is at 100% SOC.

And (seventh) repeating the step (fifth) and the step (sixth), and changing the discharge multiplying power in the step (fifth), and recording the discharge parameters of the electrochemical device.

The parameters of the electrochemical device such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and dc resistance are shown in table 1.

TABLE 1

Referring to table 1, fig. 24 and fig. 25, the electrochemical device of example 1 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, so that more electric energy can be supplied to the electric equipment. The electrochemical device can achieve a discharge capacity even exceeding the rated capacity when discharged at a high rate of 15C.

The electrochemical device of example 1 has an internal resistance of only 6 milliohms (mΩ), and has a small energy loss during discharge at a high rate of 15C-20C, thereby improving the discharge capacity of the electrochemical device and the discharge performance of the electrochemical device.

Example 2

The method of manufacturing the electrochemical device of example 2 is different from the method of manufacturing the electrochemical device of example 1 in that: the positive electrode active material of the positive electrode sheet of example 2 was LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 。

The electrochemical device testing method of example 2 is the same as the electrochemical device testing method of example 1.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 2 are shown in table 2.

TABLE 2

Referring to table 2, the electrochemical device of example 2 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Example 3

The method for manufacturing an electrochemical device of example 3 is different from the method for manufacturing an electrochemical device of example 1 in that: the positive electrode active material of the positive electrode sheet of example 3 was LiNi _0.95 Co _0.01 Mn _0.04 O ₂ 。

The electrochemical device testing method of example 3 is the same as the electrochemical device testing method of example 1.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 3 are shown in table 3.

TABLE 3 Table 3

Referring to table 3, the electrochemical device of example 3 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Example 4

Fabrication of electrochemical device。

< production of Positive electrode sheet >

The difference from example 1 is that the positive electrode sheet adopts the structure of the first sheet shown in fig. 10 and 11. Specifically, referring to fig. 10 and 11, l1=l2=1.36m, w2 is 63.2mm, w1 is 4mm, and w4 is 3.2mm. The corners of the outer and inner ends of the first blank foil zone in the winding direction are provided with identical triangular cuts, wherein la=w1=4mm, w3= 0.5W1 =2 mm.

< preparation of negative electrode sheet >

The difference from example 1 is that the negative electrode tab adopts the structure of the first tab shown in fig. 10 and 11. Referring to fig. 10 and 11, l1=l2=1.460 m, w2 is 64.1mm, w1 is 4mm, and w4 is 3.2mm. The corners of the outer and inner ends of the first blank foil zone in the winding direction are provided with identical triangular cuts, wherein la=w1=4mm, w3= 0.5W1 =2 mm. The shape and the size of the notch of the negative electrode plate are the same as those of the notch of the positive electrode plate.

< preparation of separator >

The same as in example 1.

< preparation of electrolyte >

The same as in example 1.

< preparation of electrochemical device >

The same as in example 1.

An electrochemical device was prepared according to the above method.

The electrochemical device testing method of example 4 is the same as the electrochemical device testing method of example 1.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 4 are shown in table 4.

TABLE 4 Table 4

Referring to table 4, the electrochemical device of example 4 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Example 5

Fabrication of electrochemical device。

< production of Positive electrode sheet >

The difference from example 1 is that the positive electrode sheet adopts the structure of the first sheet shown in fig. 14. Specifically, referring to fig. 14, l2=1.36 m. The first pole piece includes 10 first sub-tabs altogether, and the size of 10 first sub-tabs is the same, and the total length L3 (K1+K2+ … … +K10) of 10 first sub-tabs is 1.1m, and adjacent two first sub-tab intervals are equal, and D is 20mm, and along the length direction after the first pole piece is expanded, the inner spacing distance D1 of first empty foil region and the inner spacing distance D1 of first main part district is 40mm, and the outer end of first empty foil region and the outer spacing second distance D2 of first main part district are 40mm. W2 was 63.2mm, W1 was 4mm, and W4 was 3.2mm.

< preparation of negative electrode sheet >

The difference from example 1 is that the negative electrode tab adopts the structure of the first tab shown in fig. 14. Referring to fig. 14, L2 is 1.464m. The first pole piece comprises 10 first sub-pole lugs, the 10 first sub-pole lugs have the same size, and the total length L3 (K1+K2+ … … +K10) of the 10 first sub-pole lugs is 1.2m; the distance between two adjacent first sub-tabs is equal, D is 20mm, the first distance D1 between the inner end of the first empty foil area and the inner end of the first main body area is 42mm along the length direction of the unfolded first pole piece, and the second distance D2 between the outer end of the first empty foil area and the outer end of the first main body area is 42mm. W2 is 64.1mm, W1 is 4mm, and W4 is 3.2mm.

< preparation of separator >

The same as in example 1.

< preparation of electrolyte >

The same as in example 1.

< preparation of electrochemical device >

The same as in example 1.

An electrochemical device was prepared according to the above method.

The electrochemical device testing method of example 5 is the same as the electrochemical device testing method of example 1.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 5 are shown in table 5.

TABLE 5

Referring to table 5, the electrochemical device of example 5 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Comparative example 1

INR21700-40T (21700 cell)

The test method of the INR21700-40T cell of comparative example 1 was the same as the test method of the electrochemical device of example 1.

The parameters of the INR21700-40T cell of comparative example 1 such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and dc resistance are shown in table 6.

TABLE 6

Referring to tables 1 to 6, the electrochemical devices of examples 1 to 5 have lower energy loss and higher discharge capacity when discharged at a high rate of 15C to 20C, compared to INR21700-40T cells.

Referring to Table 6, INR21700-40T cells when discharged at a rate of 20C, the Current Interrupt Device (CID) of the cell activates and opens the discharge circuit, and INR21700-40T cells release only a portion of their capacity. Illustratively, a battery tester (New CT-4016-5V-100A) can measure the capacity that is released from 100% SOC to CID start-up, 2643mAh in Table 6.

Referring to table 6, the inr21700-40T cell had a higher internal temperature of the cell when discharged at a rate of 15C-20C, and had a larger influence on the electrolyte performance, affecting the discharge performance and discharge capacity.

Example 6

Fabrication of electrochemical device。

< production of Positive electrode sheet >

Lithium nickel cobalt manganese nickel 91 (LiNi _0.91 Co _0.04 Mn _0.05 O ₂ ) Polyvinylidene fluoride (PVDF, weight average molecular weight 7X 10) ⁶ ) Mixing conductive carbon black according to a mass ratio of 96:2:2, adding N-methyl pyrrolidone (NMP) as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the anode slurry with the solid content of 75wt% and uniform system. Uniformly coating positive electrode slurry on a positive electrode current collector aluminum foil with the thickness of 12 mu mDrying at 90deg.C to obtain a positive electrode sheet with single-side coated positive electrode active material (the coating weight per unit area of positive electrode active material on single side of positive electrode sheet is 198mg/1540.25 mm) ² ). And repeating the steps on the other surface of the aluminum foil to obtain the positive electrode plate with the double-sided coating of the positive electrode active material. And then cold pressing and cutting to obtain the positive pole piece for standby.

Illustratively, referring to fig. 6 and 7, the positive electrode tab adopts a similar structure to the first tab. Specifically, l1=l2=0.92 m. W2 is 59mm, W1 is 4mm, and W4 is 3.2mm.

< preparation of negative electrode sheet >

Artificial graphite, conductive carbon black, styrene butadiene rubber (SBR, weight average molecular weight of 5×10) ⁶ ) Mixing according to the mass ratio of 97.5:1.3:1.2, adding deionized water as a solvent, and uniformly stirring under the action of a vacuum stirrer to obtain the anode slurry with the solid content of 51wt% and uniform system. Uniformly coating the anode slurry on one surface of an anode current collector copper foil with the thickness of 8 mu m, and drying at 90 ℃ to obtain an anode sheet with an anode active material layer coated on one side (the coating weight of the anode active material on one side of the anode sheet is 103mg/1540.25mm per unit area) ² ). And repeating the steps on the other surface of the copper foil to obtain the negative electrode plate with the double-sided coating negative electrode active material layer. And cold pressing and cutting to obtain the negative electrode plate for standby.

Illustratively, referring to fig. 6 and 7, the negative electrode tab adopts a similar structure to the first tab. Specifically, l1=l2=1.02m. W2 was 60.2mm, W1 was 4mm, and W4 was 3.2mm.

< preparation of separator >

An alumina coating layer was provided on one surface of the base film to prepare a separator. Wherein, the base film is a polyethylene film with the thickness of 8 mu m, and the thickness of the alumina coating is 2 mu m.

< preparation of electrolyte >

Mixing Ethylene Carbonate (EC) and ethylmethyl carbonate (EMC) according to a mass ratio of 70:30 under the environment with water content of less than 10ppm to obtain a nonaqueous organic solvent, and then adding the nonaqueous organic solvent into the solventAdding lithium hexafluorophosphate (LiPF) into organic solvent ₆ ) And an additive fluoroethylene carbonate (FEC) are dissolved and uniformly mixed to obtain an electrolyte. Wherein based on the mass of the electrolyte, liPF ₆ 15% by mass, 1% by mass of fluoroethylene carbonate and the balance of non-aqueous organic solvent.

< preparation of electrochemical device >

And stacking and winding the prepared negative electrode plate, the prepared diaphragm and the prepared positive electrode plate in sequence to obtain the electrode assembly with the winding structure. The electrode assembly is arranged in an aluminum shell, and an electrochemical device is obtained through the technological processes of roll edge, liquid injection, formation, degassing, shaping and the like, wherein the electrochemical device is a 18650 lithium ion battery cell with the diameter of 18 mm. The formation process comprises the following steps: the electrochemical device was charged to 3.3V at a constant current of 0.02C and then to 3.6V at a constant current of 0.1C at 25 ℃.

An electrochemical device was prepared according to the above method.

Electrochemical device testing method

The parameters of the electrochemical device such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and dc resistance are shown in table 7.

TABLE 7

Referring to table 7, the electrochemical device of example 6 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer. The electrochemical device can achieve a discharge capacity even exceeding the rated capacity when discharged at a high rate of 15C.

The electrochemical device of example 6 has an internal resistance of 8.5 milliohms (mΩ), and has less energy loss during discharge at a high rate of 15C-20C, thereby improving the discharge capacity of the electrochemical device and improving the discharge performance of the electrochemical device.

Example 7

The method for manufacturing the electrochemical device of example 7 is different from the method for manufacturing the electrochemical device of example 6 in that: the positive electrode active material of the positive electrode sheet of example 7 was LiNi _0.8 Co _0.1 Mn _0.1 O ₂ 。

The electrochemical device testing method of example 7 is the same as the electrochemical device testing method of example 6.

The parameters of the electrochemical device of example 7 such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and dc resistance are shown in table 8.

TABLE 8

Referring to table 8, the electrochemical device of example 7 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Example 8

The method for manufacturing the electrochemical device of example 8 is different from the method for manufacturing the electrochemical device of example 6 in that: the positive electrode active material of the positive electrode sheet of example 8 was LiNi _0.95 Co _0.01 Mn _0.04 O ₂ 。

The electrochemical device test method of example 8 is the same as the electrochemical device test method of example 6.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 8 are shown in table 9.

TABLE 9

Referring to table 9, the electrochemical device of example 8 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Example 9

Fabrication of electrochemical device。

< production of Positive electrode sheet >

The difference from example 6 is that the positive electrode sheet adopts the structure of the first sheet shown in fig. 10 and 11. Specifically, referring to fig. 10 and 11, l1=l2=0.92 m. W2 is 59mm, W1 is 4mm, and W4 is 3.2mm. The corners of the outer and inner ends of the first blank foil zone in the winding direction are provided with identical triangular cuts, wherein la=w1=4mm, w3= 0.5W1 =2 mm.

< preparation of negative electrode sheet >

The difference from example 6 is that the negative electrode tab adopts the structure of the first tab shown in fig. 10 and 11. Referring to fig. 10 and 11, l1=l2=1.02 m, w2 is 60.2mm, w1 is 4mm, and w4 is 3.2mm. The corners of the outer and inner ends of the first blank foil zone in the winding direction are provided with identical triangular cuts, wherein la=w1=4mm, w3= 0.5W1 =2 mm. The shape and the size of the notch of the negative electrode plate are the same as those of the notch of the positive electrode plate.

< preparation of separator >

The same as in example 6.

< preparation of electrolyte >

The same as in example 6.

< preparation of electrochemical device >

The same as in example 6.

An electrochemical device was prepared according to the above method.

The electrochemical device test method of example 9 is the same as the electrochemical device test method of example 6.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 9 are shown in table 10.

Table 10

Referring to table 10, the electrochemical device of example 9 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electric energy to the consumer.

Example 10

Fabrication of electrochemical device。

< production of Positive electrode sheet >

The difference from example 1 is that the positive electrode sheet adopts the structure of the first sheet shown in fig. 14. Specifically, referring to fig. 14, L2 is 0.92m, the first pole piece includes 10 first sub-tabs altogether, the sizes of the 10 first sub-tabs are the same, the total length L3 (k1+k2+ … … +k10) of the 10 first sub-tabs is 0.8m, the distance between two adjacent first sub-tabs is equal, D is 10mm, the first distance D1 between the inner end of the first empty foil region and the inner end of the first main body region is 15mm along the length direction of the first pole piece after being unfolded, and the second distance D2 between the outer end of the first empty foil region and the outer end of the first main body region is 15mm. W2 is 59mm, W1 is 4mm, and W4 is 3.2mm.

< preparation of negative electrode sheet >

The difference from example 1 is that the negative electrode tab adopts the structure of the first tab shown in fig. 14. Referring to fig. 14, L2 is 1.02m, the first pole piece includes 10 first sub-tabs in total, the 10 first sub-tabs are identical in size, and the total length L3 (k1+k2+ … … +k10) of the 10 first sub-tabs is 0.9m; the distance D between two adjacent first sub-tabs is equal, D is 10mm, the first distance D1 between the inner end of the first empty foil area and the inner end of the first main body area is 15mm along the length direction of the unfolded first pole piece, and the second distance D2 between the outer end of the first empty foil area and the outer end of the first main body area is 15mm. W2 was 60.2mm, W1 was 4mm, and W4 was 3.2mm.

< preparation of separator >

The same as in example 6.

< preparation of electrolyte >

The same as in example 6.

< preparation of electrochemical device >

The same as in example 6.

An electrochemical device was prepared according to the above method.

The electrochemical device testing method of example 10 is the same as the electrochemical device testing method of example 6.

Parameters such as ambient temperature, discharge rate, and corresponding discharge capacity, rated capacity, and direct current resistance of the electrochemical device of example 10 are shown in table 11.

TABLE 11

Referring to table 11, the electrochemical device of example 10 has low energy loss when discharging at a high rate of 15C-20C, and the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device is greater than or equal to 99%, which can provide more electrical energy to the consumer.

Comparative example 2

INR18650-25R (18650 cells);

the test method of INR18650-25R cells of comparative example 2 was the same as the test method of electrochemical device of example 6.

The environmental temperature, discharge rate and corresponding discharge capacity, rated capacity, DC resistance and other parameters of the INR18650-25R cells of comparative example 2 are shown in Table 12.

Table 12

Referring to tables 7 to 12, the electrochemical devices of examples 6 to 10 have lower energy loss and higher discharge capacity when discharged at a high rate of 15C to 20C, compared to INR18650-25R cells.

Referring to Table 12, INR18650-25R cells, when discharged at a rate of 20C, the current cutoff device (CID) of the cell activates and opens the discharge circuit, and INR18650-25R cells release only a portion of their capacity. Illustratively, a battery tester (New CT-4016-5V-100A) can measure the capacity that is released from 100% SOC to CID start-up, i.e., 2063mAh in Table 6.

Referring to table 12, the inr18650-25R cell has a higher internal temperature of the cell when discharged at a rate of 15C-20C, and has a larger influence on the electrolyte performance, affecting the discharge performance and discharge capacity.

Claims

1. An electrochemical device comprising a case and an electrode assembly accommodated in the case, characterized in that,

the electrode assembly comprises a first electrode plate, a second electrode plate and a diaphragm, wherein the first electrode plate, the diaphragm and the second electrode plate are laminated and wound along the winding direction, one of the first electrode plate and the second electrode plate is an anode electrode plate, and the other electrode plate is a cathode electrode plate;

the first pole piece comprises a first current collector and a first active substance arranged on the first current collector, the first current collector comprises a first main body area and a first empty foil area, the first active substance is arranged in the first main body area, the arrangement direction of the first main body area and the first empty foil area is perpendicular to the winding direction,

The first empty foil area comprises a first flattening area, and the first flattening area is far away from the first main body area;

the electrochemical device is configured to:

in response to the electrochemical device at 100% SOC performing a discharge operation at a first ambient temperature at a first discharge rate, continuing the discharge operation until the SOC of the electrochemical device is 0%, the ratio of the discharge capacity of the electrochemical device to the rated capacity of the electrochemical device being greater than or equal to 90%;

2. The electrochemical device according to claim 1, wherein a ratio of a discharge capacity of the electrochemical device to a rated capacity of the electrochemical device is 95% or more.

3. The electrochemical device according to claim 2, wherein a ratio of a discharge capacity of the electrochemical device to a rated capacity of the electrochemical device is 98% or more.

4. The electrochemical device of any one of claims 1-3, wherein the first discharge rate is in the range of 17.5C-20C.

5. The electrochemical device of any one of claims 1-4, wherein the first ambient temperature is 25 ℃.

6. The electrochemical device of any one of claims 1-5, wherein the first empty foil region has a dimension W1 in the width direction of the first pole piece after being unfolded, and the first current collector has a total dimension W2, W1 and W2 satisfying: W1/W2 is more than or equal to 0.05 and less than or equal to 0.1.

7. The electrochemical device of claim 6, wherein the first flattened area has a dimension W4, 0.6-W4/W1-0.95 along the width of the first pole piece after deployment.

8. The electrochemical device according to claim 6 or 7, wherein a corner of an outer end of the first empty foil area in the winding direction is provided with a first cutout;

the size of the first notch is La along the length direction of the unfolded first pole piece;

la and W1 satisfy: la/W1 is more than or equal to 0.2 and less than or equal to 4.

9. The electrochemical device of claim 8, wherein the first cutout has a dimension W3 in the width direction of the first pole piece after being developed;

w3 and W1 satisfy: W3/W1 is more than or equal to 0.2 and less than or equal to 1.

10. The electrochemical device of any one of claims 1-9, wherein the first empty foil region has a dimension L1 along the length of the first pole piece after deployment, and the first body region has dimensions L2, L1 and L2 satisfying: L1/L2 is more than or equal to 0.8 and less than or equal to 1.

11. The electrochemical device of any one of claims 1-10, further comprising an insulator surrounding the outer side of the first flattened region, wherein an overlap region is provided at a surrounding interface of the insulator, the overlap region avoiding an outer end of the first flattened region in a winding direction.

12. The electrochemical device of any one of claims 1-11, further comprising a first electrode terminal disposed on the case and a current collecting tray connecting the first flattened region and the first electrode terminal, the current collecting tray being provided with a through hole.

13. The electrochemical device according to any one of claims 1 to 12, wherein,

the positive electrode plate comprises a positive electrode current collector and a positive electrode active substance, wherein the positive electrode active substance is arranged on the positive electrode current collector, and the positive electrode active substance comprises Li _1+a Ni _x1 Co _y1 Mn _z1 O ₂ Or Li (lithium) _1+a Ni _x2 Co _y2 Al _z2 O ₂ At least one of (a)One of the two;

wherein x1 and x2 are both greater than or equal to 0.8, y1 and y2 are both greater than 0, z2 and z3 are both greater than 0, x1+y1+z1=1, x2+y2+z2=1, -0.05.ltoreq.a.ltoreq.0.2.

14. The electrochemical device of claim 13, wherein x1 and x2 are each greater than or equal to 0.9.

15. The electrochemical device of any one of claims 1-14, wherein the negative electrode tab comprises a negative electrode current collector and a negative electrode active material comprising artificial graphite and/or natural graphite.

16. The electrochemical device of any one of claims 1-15, further comprising an electrolyte contained within the housing;

the electrolyte comprises 12-16% by mass of lithium hexafluorophosphate and 0.8-1.5% by mass of fluoroethylene carbonate based on the mass of the electrolyte.

17. The electrochemical device of any one of claims 1-16, wherein the electrochemical device comprises a cylindrical cell having a diameter of 17mm-22mm and a height of 64mm-72mm.

18. The electrochemical device of claim 17, wherein the cylindrical cell is a 18650-type cell or a 21700-type cell.

19. The electrochemical device of any one of claims 1-18, wherein the electrochemical device has a rated capacity of 2500 milliamperes per hour to 4500 milliamperes per hour.

20. The electrochemical device of any one of claims 1-19, wherein at the first ambient temperature, the direct current resistance of the electrochemical device is less than or equal to 10 milliohms.

21. A battery pack comprising the electrochemical device according to any one of claims 1 to 20.

22. The battery pack according to claim 21, wherein the battery pack includes one battery module or a plurality of the battery modules arranged in parallel, and one battery module includes a plurality of the electrochemical devices arranged in series.

23. A powered device comprising a battery pack according to any one of claims 21-22.