Full-tab lithium ion battery and electric equipment

Abstract

The invention relates to the technical field of lithium ion batteries, and discloses a full-tab lithium ion battery and electric equipment. According to the full-tab lithium ion battery, positive electrode active material particles comprise a first target element, and in the surfaces of the positive electrode active material particles, the mass percentage content of the first target element is a%; and in the whole material of the positive electrode active material particles of the positive electrode active material coating, the mass percentage content of the first target element is a '%, the full-tab lithium ion battery is charged to be overcharged at a preset current rate, the initial gas production voltage of the full-tab lithium ion battery is Vg (V), and Vg is larger than or equal to 4.5 + (a-a ') / 20; wherein the first target element comprises a first type of element and a second type of element, and the calculation mode of the mass percentage content of the first target element is the sum of the mass percentage content of the second type of element converted by a first preset proportionality coefficient and the mass percentage content of the first type of element.

Description

Technical Field

[0001] This application relates to the technical field of lithium-ion batteries, and particularly to a full-tab lithium-ion battery and an electrical device using the same. Background Art

[0002] Currently, the full-tab lithium-ion battery can significantly reduce the ohmic impedance through the full-tab structure, thereby improving the rate performance of the battery cell and enabling charge and discharge applications at high rates.

[0003] In the process of implementing the embodiments of the present disclosure, it is found that at least the following problems exist in the related art:

[0004] Due to the stacking of the tabs in the full-tab structure, the battery core forms a relatively closed space in the battery case, resulting in a significant reduction in the rate of gas escape from the active material layer. If a large number of side reactions occur in the battery cell, gas will accumulate in the battery core, causing voids between the electrode and the separator and deteriorating the interface between them, and even causing deformation of the battery case structure. At the same time, the battery cell needs to have a certain gas generation capacity under conditions such as overcharging and short-circuiting, so that the current interrupt device (CID) of the lithium-ion battery can operate normally to form a power-off protection mechanism and avoid potential safety hazards. Therefore, how to balance the gas generation capacity and safety performance of the battery while ensuring the high-rate performance of the battery has become a technical problem that needs to be solved urgently by those skilled in the art.

[0005] It should be noted that the information disclosed in the above background art section is only used to enhance the understanding of the background of this application, and therefore may include information that does not constitute the prior art known to those of ordinary skill in the art. Summary of the Invention

[0006] To provide a basic understanding of some aspects of the disclosed embodiments, a simple summary is given below. This summary is not a comprehensive review, nor is it intended to identify key / important elements or delineate the scope of protection of these embodiments. Instead, it serves as a preamble to the detailed description that follows.

[0007] Embodiments of the present disclosure provide a full-tab lithium-ion battery and an electrical device using the same to balance the gas generation capacity and safety performance of the battery, so that gas can be effectively generated and distributed in the battery core at a reasonable rate, and gas can be generated extremely quickly under special conditions to trigger the protection mechanism of the battery.

[0008] In some embodiments, the all-pole-ear lithium-ion battery of the present application includes a wound core formed by winding a positive electrode sheet, a negative electrode sheet, and a separator therebetween. Among them, at least one surface of the positive electrode sheet has a positive electrode active material coating, the positive electrode active material coating includes positive electrode active material particles, the positive electrode active material particles include a first target element, and the mass percentage of the first target element in the surface of the positive electrode active material particles is a%; and, in the overall material of the positive electrode active material particles of the positive electrode active material coating, the mass percentage of the first target element is a’%.

[0009] Charge the all-pole-ear lithium-ion battery to overcharge at a preset current rate, and the initial gas generation voltage of the all-pole-ear lithium-ion battery is Vg (V), and Vg satisfies the following relationship:[[]]

[0010] Vg≥4.5+(a - a’) / 20;

[0011] Among them, the first target element includes a first type of element and a second type of element, and the calculation method of the mass percentage of the first target element is: the sum of the mass percentage of the second type of element after being converted by a first preset proportional coefficient and the mass percentage of the first type of element.[[]]

[0012] Optionally, the positive electrode active material particles further include a second target element. In the surface of the positive electrode active material particles, the mass percentage of the second target element is b%; and, in the overall material of the positive electrode active material particles of the positive electrode active material coating, the mass percentage of the second target element is b’%; charge the all-pole-ear lithium-ion battery to overcharge at a preset current rate, and the total gas generation capacity of the all-pole-ear lithium-ion battery is Cap (mAh), and Cap satisfies the following relationship:[[]]

[0013] 3*b’ - a’≥Cap≥b’ - 2*a’;

[0014] Among them, 98%≤b’ / b≤104%; the second target element includes a third type of element and a fourth type of element, and the calculation method of the mass percentage of the second target element is: the sum of the mass percentage of the fourth type of element after being converted by a second preset proportional coefficient and the mass percentage of the third type of element.[[]]

[0015] Optionally, at least one surface of the negative electrode sheet has a negative electrode active material coating, and the gas escape ability of the all-pole-ear lithium-ion battery is P (ml), and P satisfies the following relationship:[[]]

[0016] 0.63*Cap≥P≥0.42*Cap - S + -2*S - ;

[0017] Among them, S+ is the specific surface area of the positive electrode active material coating, S - is the specific surface area of the negative electrode active material coating.

[0018] Optionally, within the voltage range of 4.3 - 4.7V, the capacity of the all - tab lithium - ion battery is M (mAh), and M satisfies the following relationship:

[0019] M≥0.9*Cap.

[0020] Optionally, the positive electrode active material particles include lithium nickel cobalt manganate and / or lithium nickel cobalt aluminate,

[0021] wherein, the atomic ratio of nickel atoms in the positive electrode active material particles is greater than or equal to 80%.

[0022] Optionally, the positive electrode active material coating further includes a positive electrode binder and a positive electrode conductive agent. The positive electrode binder includes polyvinylidene fluoride PVDF, and the positive electrode conductive agent includes one or more of acetylene black, carbon nanotubes, and graphene.

[0023] Optionally, the negative electrode active material coating includes negative electrode active material particles, and the negative electrode active material particles include one or more of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, and silicon - based materials.

[0024] Optionally, the negative electrode active material coating further includes a negative electrode dispersant, a negative electrode binder, and a negative electrode conductive agent. The negative electrode dispersant includes carboxymethyl cellulose CMC, and the negative electrode binder includes polyacrylate PAA.

[0025] Optionally, the solid substances in the negative electrode active material coating are dispersed in deionized water to form a negative electrode slurry. The content of the solid substances in the negative electrode slurry is 30 - 55%, and the solid substances in the negative electrode slurry include at least 94 - 98.5wt% of negative electrode active material particles, 0.5 - 2wt% of negative electrode conductive agent, 0.5 - 2wt% of negative electrode dispersant, and 0.5 - 2wt% of negative electrode binder, and 0 - 35wt% of the negative electrode active material particles is silicon - based material.

[0026] In some embodiments, the electrical device includes the all - tab lithium - ion battery as described in this application.

[0027] The all - tab lithium - ion battery and the electrical device provided by the embodiments of the present disclosure can achieve the following technical effects:

[0028] By regulating the mass percentage content of the first target element in the overall material of the surface of the positive electrode active material particles and the positive electrode active material coating, with the first type of element in the first target element as the main body and the second type of element in the first target element as the auxiliary, the oxygen stability of the interface between the battery electrode sheet and the separator is improved, thereby achieving precise control of the initial gas generation voltage. At the same time, controlling the difference between the content of the first target element on the surface of the positive electrode active material particles and the content of the first target element in the overall material of the positive electrode active material coating can affect the energy level difference between the surface layer interface and the overall material, thereby further increasing the gas generation voltage. In this way, the all-pole-ear lithium-ion battery of the present application realizes precise regulation of the gas generation ability of the wound core, and can balance the gas generation ability and safety performance of the battery while ensuring that the battery has high-rate performance.

[0029] The above general description and the following description are only exemplary and explanatory, and are not used to limit the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] One or more embodiments are exemplarily illustrated by the corresponding drawings. These exemplary illustrations and the drawings do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings are shown as similar elements. The drawings do not constitute a proportional limitation, and among them:

[0031] Figure 1 is a schematic structural diagram of an all-pole-ear lithium-ion battery in the related art;

[0032] Figure 2 is a schematic external structure diagram of an all-pole-ear lithium-ion battery provided by an embodiment of the present disclosure;

[0033] Figure 3 is a schematic cross-sectional structure diagram of an all-pole-ear lithium-ion battery provided by an embodiment of the present disclosure;

[0034] Figure 4 is a schematic unfolded structure diagram of an all-pole-ear lithium-ion battery provided by an embodiment of the present disclosure;

[0035] Figure 5 is an actual assembly diagram of an all-pole-ear lithium-ion battery provided by an embodiment of the present disclosure.

[0036] REFERENCE SIGNS:

[0037] 1 - cover body; 2 - end face pole ear; 3 - wound core; 4 - housing; 5 - positive electrode sheet; 6 - negative electrode sheet; 7 - separator. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0038] In order to understand the features and technical content of the embodiments of the present disclosure in more detail, the implementation of the embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The attached drawings are for reference and illustration only, and are not used to limit the embodiments of the present disclosure. In the following technical description, for the sake of explanation, numerous details are provided to give a full understanding of the disclosed embodiments. However, one or more embodiments can still be implemented without these details. In other cases, well-known structures and devices may be shown in a simplified manner to simplify the drawings.

[0039] In the description of the embodiments of the present disclosure, the terms "first", "second", etc. in the specification, claims and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged under appropriate circumstances, so as to implement the embodiments of the present disclosure described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion.

[0040] In the embodiments of the present disclosure, the orientation or positional relationship indicated by the terms "upper", "lower", "inner", "middle", "outer", "front", "rear", etc. is based on the orientation or positional relationship shown in the drawings. These terms are mainly used to better describe the embodiments of the present disclosure and their implementations, and are not used to limit that the indicated devices, elements or components must have a specific orientation, or be constructed and operated in a specific orientation. And, in addition to being able to represent an orientation or positional relationship, some of the above terms may also be used to represent other meanings. For example, the term "upper" may also be used to represent a certain attachment relationship or connection relationship in some cases. For those of ordinary skill in the art, the specific meanings of these terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0041] In addition, the terms "arranged", "connected", "fixed" should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral structure; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, or there is internal communication between two devices, elements or components. For those of ordinary skill in the art, the specific meanings of the above terms in the embodiments of the present disclosure can be understood according to specific circumstances.

[0042] Unless otherwise specified, the term "plurality" means two or more.

[0043] In the embodiments of the present disclosure, the character " / " indicates that the objects before and after are in an "or" relationship. For example, A / B means: A or B.

[0044] The term "and / or" is an associative relationship describing an object, indicating that three relationships can exist. For example, A and / or B means: A or B, or, A and B these three relationships.

[0045] It should be noted that, without conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other.

[0046] Lithium-ion batteries have been widely used in key national fields such as new energy vehicles, port heavy machinery, and military industry due to their high energy density, long cycle life, and strong environmental adaptability. According to their electrochemical characteristics, they can be divided into power-type lithium-ion batteries and energy-type lithium-ion batteries. Power-type lithium-ion batteries have both energy density and power density, and can achieve rapid energy replenishment, thus becoming a key development direction for emerging energy storage devices. Among the many research and development system directions of power-type lithium-ion batteries, all-pole-ear lithium-ion batteries have become the key development direction of current power-type lithium-ion batteries due to their typical advantages such as low connection internal resistance, strong connection reliability, and strong heat dissipation effect.

[0047] In the related art, as shown in Figure 1 , an all-pole-ear lithium-ion battery generally includes a housing 4, a wound core 3, and a cover 1. Among them, the housing 4 and the cover 1 jointly enclose an inner cavity, and the wound core 3 is arranged in the inner cavity. The welding of the wound core 3 and the housing 4 can first use a tooling fixture to fix the spatial positions of the wound core 3 and the housing 4, then use a press to insert the wound core 3 into the housing and ensure that the positive end face of the wound core 3 is in reliable contact with the lower end face inside the housing 4, and then use the beam emitted by a laser welding machine to fixedly connect the wound core 3 and the housing 4. The wound core 3 is a wound structure, and its two ends respectively include a positive aluminum foil all-pole ear and a negative copper foil all-pole ear. The positive aluminum foil all-pole ear and the negative copper foil all-pole ear are flattened and shaped to form end face pole ears 2, that is, a positive end face pole ear and a negative end face pole ear. Both the positive end face pole ear and the negative end face pole ear are welded to the structure of the cover 1, and one end of the structure of the cover 1 is an integrated structure with the housing 4.

[0048] Therefore, in order to solve the technical problems existing in the related art, as shown in Figures 2 to 5As shown in the figure, an embodiment of the present disclosure provides a full-tab lithium-ion battery, including a wound core 3 formed by winding a positive electrode sheet 5, a negative electrode sheet 6, and a separator 7 therebetween. Among them, at least one surface of the positive electrode sheet 5 has a positive electrode active material coating, and the positive electrode active material coating includes positive electrode active material particles. At least one surface of the negative electrode sheet 6 has a negative electrode active material coating, and the negative electrode active material coating includes negative electrode active material particles. Moreover, the positive electrode active material particles include a first target element. In the surface of the positive electrode active material particles, the mass percentage content of the first target element is a%. The content test method can be that after disassembling the full-tab lithium-ion battery to obtain the positive electrode sheet, it is washed three times with dimethyl carbonate, dried at 50°C for 1 hour, a CP cross-section is made of the positive electrode sheet, and then a scanning electron microscope SEM is used in conjunction with an energy dispersive spectrometer EDS elemental analysis test to obtain a mass percentage content of a%. And, in the overall material of the positive electrode active material particles in the positive electrode active material coating, the mass percentage content of the first target element is a'%. The content test method can be that after disassembling the full-tab lithium-ion battery to obtain the positive electrode sheet, it is washed three times with dimethyl carbonate, dried at 50°C for 1 hour, the positive electrode sheet powder is scraped with a ceramic spoon, and an XPS test is performed to obtain a mass percentage content of a'%.

[0049] Charge the full-tab lithium-ion battery to overcharge at a preset current rate. The initial gas generation voltage of the full-tab lithium-ion battery is Vg (V), and Vg satisfies the following relationship:

[0050] Vg≥4.5+(a - a') / 20;

[0051] Among them, the first target element includes a first type of element and a second type of element, and the calculation method of the mass percentage content (a% and a'%) of the first target element is: the sum of the mass percentage content of the second type of element after being converted by a first preset proportional coefficient and the mass percentage content of the first type of element.

[0052] Optionally, the first type of element in this application includes cobalt Co, and the second type of element includes one or more of boron B, zirconium Zr, scandium Sc, titanium Ti, tungsten W, boron B, strontium Sr, lanthanum La, antimony Sb, and cerium Ce. And, the first preset proportional coefficient can be selected from 10 - 30%, and preferably 20%.

[0053] Specifically, the present application can perform elemental qualitative and quantitative analysis through X-ray energy spectrum analysis. For example, in the surface of the cathode active material particles, the first type of element in the first target element is Co, and the mass percentage of Co is 8%. The second type of elements in the first target element include Zr and Ti, the mass percentage of Zr is 0.5%, and the mass percentage of Ti is 0.5%. The first preset proportionality coefficient is 20%, then a = 8% + 20%*(0.5% + 0.5%) = 8.2%. Another example, in the overall material of the cathode active material particles in the cathode active material coating, the first type of element in the first target element is Co, and the mass percentage of Co is 6%. The second type of elements in the first target element include Zr and Ti, the mass percentage of Zr is 0.4%, and the mass percentage of Ti is 0.4%. The first preset proportionality coefficient is 20%, then a = 6% + 20%*(0.4% + 0.4%) = 6.16%

[0054] By using the all-pole-ear lithium-ion battery provided in the embodiments of the present disclosure, by regulating the mass percentage of the first target element in the surface of the cathode active material particles and the overall material in the cathode active material coating, with the first type of element in the first target element as the main body and the second type of element in the first target element as the auxiliary, the oxygen stability of the interface between the battery electrode sheet and the separator is improved, thereby realizing precise control of the initial gas generation voltage. At the same time, controlling the difference between the content of the first target element on the surface of the cathode active material particles and the content of the first target element in the overall material in the cathode active material coating can affect the energy level difference between the surface layer interface and the overall material, thereby further improving the gas generation voltage. In this way, the all-pole-ear lithium-ion battery of the present application realizes precise regulation of the gas generation capacity of the wound core, and can balance the gas generation capacity and safety performance of the battery while ensuring that the battery has high-rate performance.

[0055] In the embodiments of the present application, the cathode active material particles of the present application further include a second target element. In the surface of the cathode active material particles, the mass percentage of the second target element is b%; and in the overall material of the cathode active material particles in the cathode active material coating, the mass percentage of the second target element is b'. The test method can be to obtain this data by disassembling the all-pole-ear lithium-ion battery and performing scanning electron microscopy (SEM) and energy dispersive spectrometer (EDS) elemental analysis on the cathode sheet.

[0056] Charge the all-pole-ear lithium-ion battery to overcharge at a preset current rate. The total gas generation capacity of the all-pole-ear lithium-ion battery is Cap (mAh), and Cap satisfies the following relationship:

[0057] 3*b' - a' ≥ Cap ≥ b' - 2*a';

[0058] Among them, 98% ≤ b’ / b ≤ 104%; the second target element includes the third type of element and the fourth type of element, and the calculation method of the mass percentage content (b% and b’%) of the second target element is: the sum of the mass percentage content of the fourth type of element after being converted by the second preset proportional coefficient and the mass percentage content of the third type of element.

[0059] Preferably, the chemical formula of the positive electrode active material particles of the present application is LiNi a Mn b M 1c M 2d O 2 , where 0.6 ≤ a ≤ 0.95, 0.1 ≤ b ≤ 0.3, 0.1 ≤ c ≤ 0.3, 0.01 ≤ d ≤ 0.1, M 1 is the first target element, M 1 includes one or more elements of cobalt Co, boron B, zirconium Zr, scandium Sc, titanium Ti, tungsten W, boron B, strontium Sr, lanthanum La, antimony Sb, and cerium Ce, M 2 is the second target element, M 2 includes one or more of the elements Ni, Mn, or Al.

[0060] Optionally, the third type of element of the present application includes cobalt Co and nickel Ni, and the fourth type of element includes Mn or Al. Also, the second preset proportional coefficient can be selected from 40 - 60%, preferably 50%.

[0061] In this way, by regulating the mass percentage content of the second target element on the surface of the positive electrode active material particles and in the overall material of the present application, with the third type of element in the second target element as the main body and the fourth type of element in the second target element as the auxiliary, since its oxygen stability is relatively low and it is more likely to generate more gas in the interfacial reaction, the gas generation amount at the interface between the battery electrode and the separator is thus increased, and further the triggering stability of the CID to normally actuate to form a power-off protection mechanism is improved, ensuring the high safety of the battery.

[0062] In the embodiment of the present application, the gas evolution ability of the all - tab lithium - ion battery of the present application is P (ml), and M satisfies the following relationship:

[0063] 0.63*Cap ≥ P ≥ 0.42*Cap - S + -2*S - ;

[0064] Among them, Cap is the total gas generation capacity of the all - tab lithium - ion battery, S + is the specific surface area of the positive electrode active material coating, S - is the specific surface area of the negative electrode active material coating. The specific surface area refers to the total surface area per unit mass of the material, usually in square meters per gram (m2 In units of / g. The gas evolution ability refers to the ability of gas to escape from the interface to become an independent gas state, or the ability of gas to escape from a closed system under specific conditions.

[0065] Moreover, the specific surface area can be analyzed and measured by the BET specific surface area method to obtain this data. At the same time, the total gas production capacity Cap can be obtained by analyzing the electrochemical impedance spectrum (EIS) through the relaxation time distribution function (DRT) or by the Fourier transform infrared spectroscopy FTIR test method.

[0066] Optionally, within the voltage range of 4.3 - 4.7V, the capacity of the full-tab lithium-ion battery is M (mAh), and M satisfies the following relationship:

[0067] M ≥ 0.9 * Cap.

[0068] Thus, in this application, in addition to the functions of related elements, the design of the total surface area of the positive and negative electrode active material coatings also plays an important role in the performance of the wound core. If the specific surface area is too large, the interface stability decreases and the safety performance is poor. If the specific surface area is too small, the rate performance deteriorates and it is difficult to achieve high-rate charge and discharge applications.

[0069] In the embodiments of this application, the positive electrode active material particles of this application include lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminate, wherein the atomic ratio of nickel atoms in the positive electrode active material particles is greater than or equal to 80%. At the same time, the positive electrode active material coating also includes a positive electrode binder and a positive electrode conductive agent. The positive electrode binder includes polyvinylidene fluoride PVDF, and the positive electrode conductive agent includes one or more of acetylene black, carbon nanotubes, and graphene.

[0070] In the embodiments of this application, the negative electrode active material coating of this application includes negative electrode active material particles, and the negative electrode active material particles include one or more of artificial graphite, natural graphite, mesophase carbon microspheres, hard carbon, soft carbon, and silicon-based materials (silicon oxide materials, silicon carbon materials). At the same time, the negative electrode active material coating also includes a negative electrode dispersant, a negative electrode binder, and a negative electrode conductive agent. The negative electrode dispersant includes carboxymethyl cellulose CMC, and the negative electrode binder includes polyacrylic acid PAA.

[0071] In a specific application of this embodiment, the solid substances of the negative electrode active material coating of this application are dispersed in deionized water to form a negative electrode slurry. The content of the solid substances in the negative electrode slurry is 30 - 55%, and the solid substances in the negative electrode slurry include at least 94 - 98.5wt% of negative electrode active material particles, 0.5 - 2wt% of negative electrode conductive agent, 0.5 - 2wt% of negative electrode dispersant, and 0.5 - 2wt% of negative electrode binder, and 0 - 35wt% of the negative electrode active material particles is silicon-based material.

[0072] In addition, an embodiment of the present disclosure provides an electrical device, including the all-pole-ear lithium-ion battery as described in this application.

[0073] The all-pole-ear lithium-ion battery of this application is tested in the following manner:

[0074] Test 1: Rate cycle retention test

[0075] Take a lithium-ion battery prepared according to any of the above embodiments, place it in a constant temperature oven at 25 °C for more than 4 h, and perform the test according to the following steps:

[0076] S1: Constant current discharge the battery to cut-off at 2.5 V under the condition of 0.1 C, and let it stand for 5 minutes;

[0077] S2: Constant current charge the battery to cut-off at 4.2 V under the condition of 0.2 C, and constant voltage charge it to cut-off at 0.05 C, and let it stand for 5 minutes;

[0078] S3: Constant current discharge the battery to cut-off at 2.5 V under the condition of 0.2 C, and let it stand for 5 minutes;

[0079] S4: Constant current charge the battery to 4.2 V under the condition of 3 C, and constant voltage charge it to cut-off at 0.05 C, and let it stand for 5 minutes;

[0080] S5: Constant current discharge the battery to cut-off at 2.5 V under the condition of 8 C, and let it stand for 5 minutes, and read the capacity value C1 at this time;

[0081] S6: Repeat the above steps S4 to S5 for 600 cycles;

[0082] S7: Read the discharge capacity when the battery is discharged at a constant current of 6 C to 2.5 V for the 600th time as C600. The cycle performance of a single battery can be obtained by the ratio of the discharge capacity C600 when the battery is discharged at a constant current of 8 C to 2.5 V for the 600th time and the discharge capacity C1 when the battery is discharged at a constant current of 10 C to 2.5 V for the first time. The rate cycle capacity retention rate is: (C600 / C1)*100%.

[0083] Test 2: Short-circuit safety test

[0084] Take a lithium-ion battery prepared according to any of the above embodiments, place it in a constant temperature oven at 25 °C for more than 4 h, and perform the test according to the following steps:

[0085] S1: Constant current discharge the battery to cut-off at 2.5 V under the condition of 0.1 C, and let it stand for 5 minutes;

[0086] S2: Constant current charge the battery to cut-off at 4.2 V under the condition of 0.2 C, and constant voltage charge it to cut-off at 0.05 C, and let it stand for 5 minutes;

[0087] S3: Discharge the battery at a constant current of 0.2C until it cuts off at 2.5V, and let it stand for 5 minutes;

[0088] S4: Charge the battery at a constant current of 0.2C until it cuts off at 4.2V, and then charge it at a constant voltage until it cuts off at 0.05C, and let it stand for 5 minutes;

[0089] S5: Short - circuit the positive and negative electrodes of the battery with a 20mΩ resistor, and record the voltage and temperature of the battery;

[0090] S6: If there is no fire throughout the process and the battery temperature is lower than 150°C, it is considered to pass the test; otherwise, it is considered to fail.

[0091] S7: Test 5 batteries in parallel, and the proportion of those passing is called the passing rate.

[0092] Test Three: Over - charge Test

[0093] Take a cylindrical lithium - ion battery prepared according to any of the above embodiments, place it in a constant - temperature oven at 25°C for more than 4h, and conduct the test according to the following steps:

[0094] S1: Discharge the battery at a constant current of 0.1C until it cuts off at 2.5V, and let it stand for 5 minutes;

[0095] S2: Charge the battery at a constant current of 0.2C until it cuts off at 4.2V, and then charge it at a constant voltage until it cuts off at 0.05C, and let it stand for 5 minutes;

[0096] S3: Discharge the battery at a constant current of 0.2C until it cuts off at 2.5V, and let it stand for 5 minutes;

[0097] S4: Paste temperature - sensing wires at the head, middle, and bottom of the battery cell to collect temperature signals

[0098] S5: Charge at a constant current of 3C to 6.0V, then switch to constant - voltage charging for 1h, with a sampling interval of 1s

[0099] S6: Let it stand for 30 minutes

[0100] S7: If the battery cell does not catch fire or explode and the highest temperature is not higher than 150°C, it is considered to pass. After testing 5 battery cells in parallel, calculate the passing rate.

[0101] The following continues to further explain and illustrate the present invention with embodiments and comparative examples.

[0102] Embodiment 1

[0103] Embodiment 1 of the present invention provides a full - pole - ear lithium - ion battery, which includes a housing, a wound core and an electrolyte placed in the housing. The wound core is formed by winding a positive electrode sheet, a separator and a negative electrode sheet together.

[0104] (1) Prepare the positive electrode sheet, including the positive current collector aluminum foil and the positive electrode coating coated on both surfaces of the aluminum foil; wherein, calculated by weight percentage, the positive electrode coating includes 96% of LiNi0.86Co0.05Al0.09O2 (NCA86), 0.7% of multi-walled carbon nanotube conductive agent, 1.8% of Super-P (conductive carbon black) conductive agent, and 1.5% of polyvinylidene fluoride PVDF binder; add the above substances into N-methylpyrrolidone and stir to form a positive electrode slurry with a solid content of 60%, and coat it on the positive current collector to form a positive electrode sheet.

[0105] (2) Prepare the negative electrode sheet, including the negative current collector copper foil and the negative electrode coating coated on both surfaces of the copper foil. Calculated by weight percentage, the negative electrode coating includes 93% of artificial graphite, 3% of silicon, 1.0% of conductive agent acetylene black, 1% of thickening agent CMC, and 2% of negative electrode binder polyacrylic acid.

[0106] (3) Prepare the electrolyte. Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a volume ratio of 1:1:1 to obtain an organic solvent. Then dissolve the fully dried lithium salt LiPF6 in the mixed organic solvent to prepare an electrolyte with a concentration of 1 mol / L.

[0107] (4) The separator includes a high-porosity power separator. The base film PE has a thickness of 9 μm, the ceramic coatings on both sides have a thickness of 1 μm, and the PVDF coating has a thickness of 1 μm. The air permeability of the separator is 120 s / 100 mL.

[0108] (5) After rolling, slitting, and die-cutting the positive electrode sheet and the negative electrode sheet respectively, wind them together with the separator at the same time. Use a winding machine to wind the positive electrode sheet, the negative electrode sheet, and the separator to form a wound core. Cut and stack the positive electrode tab and the negative electrode tab of the wound core, then weld the positive electrode current collector and the negative electrode current collector to the wound core respectively. Then weld the negative electrode current collector to the steel shell, place an insulating sheet above the positive electrode current collector, and weld the positive electrode current collector to the cap to obtain a lithium-ion battery wound core body, which is installed in the battery case. After completing the processes of liquid injection, sealing, and formation, the lithium-ion battery is obtained.

[0109] Example 2

[0110] Example 2 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0111] Example 3

[0112] Example 3 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0113] Example 4

[0114] Example 4 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0115] Example 5

[0116] Example 5 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0117] Comparative Example 1

[0118] Comparative Example 1 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0119] Comparative Example 2

[0120] Comparative Example 2 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0121] Comparative Example 3

[0122] Comparative Example 3 provides a full-tab lithium-ion battery, which is different from Example 1 in that the mass percentage contents of the first type of element and the second type of element in the first target element it contains are different, and the mass percentage contents of the third type of element and the fourth type of element in the second target element it contains are different.

[0123] Wherein:

[0124] The relevant data of the mass percentage contents involved in Examples 1-5 and Comparative Examples 1-3 are shown in the following table:

[0125]

[0126] Continued Table

[0127]

[0128] The relevant data of the initial gas generation voltage and total gas generation capacity involved in Examples 1-5 and Comparative Examples 1-3 are shown in the following table:

[0129]

[0130] It can be seen from the data in the above table that by controlling the content distribution of the first target element in the positive electrode sheet of the all-tab lithium-ion battery, the minimum value of the initial gas generation voltage Vg of the battery is controlled; by controlling the content distribution of the second target element in the positive electrode sheet of the all-tab lithium-ion battery, the total gas generation capacity Cap of the battery is controlled; by controlling the specific surface area and total gas generation capacity of the positive and negative electrode sheets of the all-tab lithium-ion battery, the gas escape ability of the battery is controlled to ensure the best electrochemical performance and cycle stability performance of the battery. And within the specific voltage range of 4.3-4.7V of the all-tab lithium-ion battery, the capacity of the all-tab lithium-ion battery is M (mAh), satisfying M≥0.9*Cap, which fully balances the gas generation ability and safety performance of the battery.

[0131] The relevant data of the gas escape ability and capacity involved in Examples 1-5 and Comparative Examples 1-3 are shown in the following table:

[0132]

[0133] The relevant data of the tests corresponding to each test battery in Examples 1-5 and Comparative Examples 1-3 are shown in the following table:

[0134]

[0135] From the experimental results of the above Examples 1-5 and Comparative Examples 1-3, it can be concluded that in this application, by selecting appropriate cathode materials, appropriate ratios of cathode active material coatings, and the secondary cold pressing process of the electrode sheet, the surface of the cathode active material particles and the mass percentage contents of the first target element and the second target element in the overall material are regulated. The more uniform the distribution of the target elements inside the positive electrode sheet, the higher the 3C / 8C cycle 600cls retention rate of the battery, the better the overcharge test effect, and the higher the short-circuit test passing rate. Since the oxygen stability of the set target elements is relatively low and more gases are more likely to be generated in the interfacial reaction, the gas generation amount at the interface between the battery electrode sheet and the separator is increased, and further the triggering stability of the CID to normally actuate to form a power-off protection mechanism is improved, ensuring the high safety of the battery.

[0136] In addition, by regulating the mass percentage content of the first target element in the overall material of the surface of the positive electrode active material particles and the positive electrode active material coating, with the first type of element in the first target element as the main body and the second type of element in the first target element as the auxiliary, the oxygen stability of the interface between the battery electrode sheet and the separator is improved, thereby achieving precise control of the initial gas generation voltage. At the same time, controlling the difference between the content of the first target element on the surface of the positive electrode active material particles and the content of the first target element in the overall material of the positive electrode active material coating can affect the energy level difference between the surface layer interface and the overall material, thereby further improving the gas generation voltage. In this way, the all-pole-ear lithium-ion battery of the present application realizes precise regulation of the gas generation capacity of the wound core, and can balance the gas generation capacity and safety performance of the battery while ensuring that the battery has high-rate performance.

[0137] The above description and the drawings fully illustrate the embodiments of the present disclosure so that those skilled in the art can practice them. Other embodiments may include structural and other changes. The embodiments represent only possible variations. Unless explicitly required, individual components and functions are optional, and the order of operations can vary. Parts and features of some embodiments may be included in or substituted for parts and features of other embodiments. The embodiments of the present disclosure are not limited to the structures described above and shown in the drawings, and various modifications and changes can be made without departing from its scope. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A full-ear lithium-ion battery, comprising a winding core formed by winding a positive electrode sheet, a negative electrode sheet and a separator therebetween, wherein: At least one surface of the positive electrode sheet has a positive electrode active material coating, the positive electrode active material coating includes positive electrode active material particles, characterized in that the positive electrode active material particles include a first target element, and the mass percentage of the first target element in the surface of the positive electrode active material particles is a%; and the mass percentage of the first target element in the whole material of the positive electrode active material particles of the positive electrode active material coating is a'%; The full-tab lithium-ion battery is charged to overcharge at a preset current rate, and the starting gas production voltage of the full-tab lithium-ion battery is Vg (V), and Vg satisfies the following relationship: Vg≥4.5+(a-a') / 20; The first target element includes first-category elements and second-category elements, and the mass percentage of the first target element is calculated as follows: the sum of the mass percentage of the second-category elements converted by a first preset proportional coefficient and the mass percentage of the first-category elements.

2. The full-tab lithium-ion battery according to claim 1, characterized in that: The positive electrode active material particles further include a second target element, and the mass percentage of the second target element in the surface of the positive electrode active material particles is b%; and the mass percentage of the second target element in the material of the positive electrode active material particles of the positive electrode active material coating is b'%; The full-tab lithium-ion battery is charged to overcharge at a preset current rate, and the total gas production capacity of the full-tab lithium-ion battery is Cap (mAh), and Cap satisfies the following relationship: 3*b'-a'≥Cap≥b'-2*a'; Among them, 98%≤b' / b≤104%; the second target element includes the third category element and the fourth category element, and the mass percentage of the second target element is calculated as: the sum of the mass percentage of the fourth category element converted by the second preset proportional coefficient and the mass percentage of the third category element.

3. The full-tab lithium-ion battery according to claim 2, characterized in that: At least one surface of the negative electrode sheet has a negative electrode active material coating, and the gas release capacity of the full-tab lithium-ion battery is P (ml), and P satisfies the following relationship: 0.63*Cap≥P≥0.42*Cap-S + -2*S - ; Among them, S + is the specific surface area of ​​the positive electrode active material coating, S - is the specific surface area of ​​the negative electrode active material coating.

4. The full-tab lithium-ion battery according to claim 2, characterized in that: In the voltage range of 4.3-4.7V, the capacity of the full-tab lithium-ion battery is M (mAh), and M satisfies the following relationship: M≥0.9*Cap.

5. The full-tab lithium-ion battery according to any one of claims 1 to 4, characterized in that: The positive electrode active material particles include lithium nickel cobalt manganese oxide and / or lithium nickel cobalt aluminum oxide, wherein the atomic ratio of nickel atoms in the positive electrode active material particles is greater than or equal to 80%.

6. The full-tab lithium-ion battery according to claim 5, characterized in that: The positive electrode active material coating further includes a positive electrode binder and a positive electrode conductor. The positive electrode binder includes polyvinylidene fluoride (PVDF), and the positive electrode conductor includes one or more of acetylene black, carbon nanotubes, and graphene.

7. The full-tab lithium-ion battery according to claim 3, characterized in that: The negative electrode active material coating comprises negative electrode active material particles, and the negative electrode active material particles comprise one or more of artificial graphite, natural graphite, mesophase carbon microbeads, hard carbon, soft carbon and silicon-based materials.

8. The full-tab lithium-ion battery according to claim 7, characterized in that: The negative electrode active material coating layer further includes a negative electrode dispersant, a negative electrode binder and a negative electrode conductor. The negative electrode dispersant includes carboxymethyl cellulose CMC, and the negative electrode binder includes polyacrylic acid PAA.

9. The full-tab lithium-ion battery according to claim 8, characterized in that: The solid matter of the negative electrode active material coating is dispersed in deionized water to form a negative electrode slurry, the content of the solid matter in the negative electrode slurry is 30-55%, the solid matter in the negative electrode slurry includes at least 94-98.5wt% of negative electrode active material particles, 0.5-2wt% of negative electrode conductor, 0.5-2wt% of negative electrode dispersant and 0.5-2wt% of negative electrode binder, and 0-35wt% of the negative electrode active material particles are silicon-based materials.

10. An electrical device, characterized in that: Comprising a full-tab lithium-ion battery as described in any one of claims 1 to 9.

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