Lithium ion battery and electric equipment

Abstract

The invention belongs to the technical field of new energy, and particularly relates to a lithium ion battery and electric equipment. According to the present invention, by arranging the bottom coating layer comprising at least one of the boehmite, the gibbsite and the pseudo-boehmite in the positive plate and regulating the composition and the use amount of the electrolyte, the decomposition of the lithium salt can be effectively inhibited, the increase of the impedance can be avoided, the stability of the battery at the high temperature and the high pressure can be improved, and the safety performance and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present application belongs to the field of new energy technology, and specifically relates to a lithium-ion battery and electrical equipment. Background Art

[0002] The rapid development of electric vehicles and energy storage systems has led to higher demands on the energy density, safety, and cycle life of lithium-ion batteries. Traditional solutions primarily improve safety on the positive electrode side by applying a certain thickness of ceramic coating (such as boehmite) to both sides of the positive electrode to prevent tab burrs from piercing the separator. However, these solutions have the following drawbacks: under high temperature and high pressure (charge cut-off voltage greater than or equal to 4.48V), the Al-OH groups on the boehmite surface can directly react with LiPF6 or its hydrolysis intermediates (such as PF5 or POF3) to release HF. Furthermore, boehmite can further release H2O through reactions with HF or through the presence of trace amounts of physically adsorbed water or structural water at high temperature and high pressure, exacerbating the vicious cycle of "LiPF6 hydrolysis → acid production → solvent decomposition or other reactions → water production." This also accelerates the dissolution of transition metals from the positive electrode active material layer, resulting in a decrease in cycle life and safety.

[0003] Therefore, it is of great practical significance to develop a lithium-ion battery technology that can improve the high-temperature safety performance and cycle performance of high-voltage positive electrodes. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present application is to overcome the defects of the prior art such as poor high-temperature safety performance and cycle performance of the positive electrode under high voltage, thereby providing a lithium-ion battery and electrical equipment.

[0005] To this end, this application provides the following technical solutions:

[0006] According to one aspect of the present application, a lithium-ion battery is provided, comprising: a positive electrode sheet, a negative electrode sheet and an electrolyte,

[0007] The positive electrode sheet comprises a positive electrode current collector and a primer layer located on at least one side of the positive electrode current collector, wherein a positive electrode active layer is provided on a surface of the primer layer away from the positive electrode current collector;

[0008] The primer layer includes at least one of boehmite, gibbsite, and pseudo-boehmite;

[0009] Based on the total mass of the electrolyte, it includes A% LiPF6, B% dinitrile, C% 1,3,6-hexanetrinitrile, and D% compound I, wherein the dinitrile includes succinonitrile and / or adiponitrile, and the compound I includes at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate;

[0010] Moreover, A, B, C, and D satisfy: 10≤A≤20, 0.5≤B≤3.5, 0.5≤C≤3.5, 3≤D≤30, 0.07≤(B+C) / A≤0.6.

[0011] In some optional embodiments, B, C, and D satisfy: 0.7≤D / (B+C)≤10;

[0012] and / or, the thickness of the primer layer is T μm, 0.5≤T≤5;

[0013] Preferably, D and T satisfy: 1≤D / T≤10.

[0014] In some optional embodiments, the electrolyte further comprises Compound II in a mass percentage of E%, 10≤E≤60;

[0015] The compound II includes at least one of propyl propionate and ethyl butyrate.

[0016] In some optional embodiments, the electrolyte further comprises 0.01%-2% lithium difluorophosphate;

[0017] And / or, the electrolyte further comprises 2% to 30% by weight of fluoroethylene carbonate;

[0018] And / or, the electrolyte further comprises 0.5%-6% by mass of 1,3-propane sultone.

[0019] In some optional embodiments, the surface of the negative electrode sheet is provided with grooves, the depth of the grooves is 3 μm-45 μm, the width is 30 μm-300 μm, and the spacing is 0.2 mm-10 mm;

[0020] Preferably, the groove is at least one of a linear groove, a grid-shaped groove, a wavy groove, an annular groove, a lattice groove, a spiral groove, a cross groove or a serrated groove.

[0021] In some optional embodiments, the length of the positive electrode active layer is L1, and the area 30% L1 to 70% L1 from the starting end of the positive electrode active layer is a middle area, and a first electrode tab groove is provided in the middle area, and a positive electrode tab is provided in the first electrode tab groove;

[0022] And / or, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the current collector, the length of the negative electrode active layer is L2, the area 30% L2 to 70% L2 away from the starting end of the positive electrode active layer is the middle area, a second electrode tab groove is provided in the middle area, and a negative electrode tab is provided in the second electrode tab groove.

[0023] In some optional embodiments, the negative electrode active layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the mass percentage of silicon element is 1.5%-50% based on the total mass of the negative electrode active layer, and the Dv50 particle size of the silicon-based material is 5-15 μm;

[0024] Preferably, the mass percentage of compound I in the electrolyte is 3%-15%;

[0025] Preferably, the mass percentage of the fluoroethylene carbonate is 12%-30%.

[0026] In some optional embodiments, the primer layer covers the entire area of ​​both side surfaces of the positive electrode current collector.

[0027] In some optional embodiments, the positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide.

[0028] According to another aspect of the present application, there is provided an electrical device comprising the above-mentioned lithium-ion battery.

[0029] The technical solution of this application has the following advantages:

[0030] The lithium-ion battery provided herein comprises: a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet comprises a positive electrode current collector, and a primer layer located on at least one surface of the positive electrode current collector, wherein a positive electrode active layer is provided on a surface of the primer layer away from the positive electrode current collector; the primer layer comprises at least one of boehmite, gibbsite, and pseudo-boehmite; and the electrolyte comprises, based on the total mass of the electrolyte, A% of LiPF6, B% of dinitrile, C% of 1,3,6-hexanetrinitrile, and D% of compound I, wherein the dinitrile comprises succinonitrile and / or adiponitrile, and the compound I comprises at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate; and A, B, C, and D satisfy the following conditions: 10≤A≤20, 0.5≤B≤3.5, 0.5≤C≤3.5, 3≤D≤30, and 0.07≤(B+C) / A≤0.6. The present application provides a base coating comprising at least one of boehmite, gibbsite, and pseudo-boehmite in the positive electrode sheet, and regulates the composition and dosage of the electrolyte, thereby effectively inhibiting the decomposition of lithium salts, avoiding the increase of impedance, improving the stability of the battery under high temperature and high pressure, and enhancing the safety performance and cycle performance of the battery.

[0031] Additional aspects and advantages of the present application will be given in part in the description below, and in part will become obvious from the description below, or will be learned through practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific implementation methods of the present application or the technical solutions in the prior art, the following is a brief introduction to the drawings required for use in the specific implementation methods or the description of the prior art. Obviously, the drawings described below are some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0033] Figure 1 This is a schematic structural diagram of the positive electrode sheet in an embodiment of the present application;

[0034] Reference numerals:

[0035] 1. Primer layer; 2. Active material layer; 3. Positive electrode current collector. DETAILED DESCRIPTION

[0036] The following examples are provided to further better understand the present application, but are not limited to the best implementation mode described herein, and do not limit the content and protection scope of the present application. Any product identical or similar to the present application obtained by anyone under the inspiration of the present application or by combining the features of the present application with other prior arts shall fall within the scope of protection of the present application.

[0037] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are for the purpose of describing specific embodiments only and are not intended to limit this application; the terms "including" and "having" and any variations thereof in this application text are intended to cover non-exclusive inclusions.

[0038] In the description of the embodiments of the present application, technical terms such as "first" and "second" are only used to distinguish different objects and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0039] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0040] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of the end values ​​and can be arbitrarily combined, i.e., any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise specified, the numerical range "ab" represents an abbreviation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" have been listed herein, and "0-5" is just an abbreviation of these numerical combinations. In addition, when stating that a parameter is an integer ≥2, it is equivalent to disclosing that the parameter can be, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0041] In the description of the embodiments of the present application, the term "and / or" is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can represent three situations: A exists alone, A and B exist at the same time, and B exists alone.

[0042] In the description of the embodiments of the present application, the term "at least one" refers to one or more than two (including two).

[0043] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), indicating that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0044] As described in the background technology, the high-temperature safety performance and cycle performance of the positive electrode under high voltage in the prior art are poor. To this end, this application provides the following technical solutions:

[0045] According to one aspect of the present application, a lithium-ion battery is provided, comprising: a positive electrode sheet, a negative electrode sheet and an electrolyte,

[0046] The positive electrode sheet comprises a positive electrode current collector and a primer layer located on at least one side of the positive electrode current collector, wherein a positive electrode active layer is provided on a surface of the primer layer away from the positive electrode current collector;

[0047] The primer layer includes at least one of boehmite, gibbsite, and pseudo-boehmite;

[0048] Based on the total mass of the electrolyte, it includes A% LiPF6, B% dinitrile, C% 1,3,6-hexanetrinitrile (HTCN), and D% compound I, wherein the dinitrile includes succinonitrile (SN) and / or adiponitrile (ADN), and the compound I includes at least one of 2,2-difluoroethyl acetate (DFEA) and ethyl 2,2-difluoroacetate;

[0049] Moreover, A, B, C, and D satisfy: 10≤A≤20, 0.5≤B≤3.5, 0.5≤C≤3.5, 3≤D≤30, 0.07≤(B+C) / A≤0.6.

[0050] As an example, the mass percentage of LiPF6 in the electrolyte can be 10%, 12%, 14%, 15%, 16%, 18%, 20%, or within the range of any of the above values; the mass percentage of the dinitrile can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or within the range of any of the above values; the mass percentage of the HTCN can be 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, or within the range of any of the above values; the mass percentage of the compound I can be 3%, 5%, 10%, 15%, 20%, 25%, 30%, or within the range of any of the above values; the value of (B+C) / A can be 0.07, 0.1, 0.15, 0.2, 0.3, 0.4, 0.5, 0.6, or within the range of any of the above values.

[0051] In the present application, by setting a primer layer on the positive electrode sheet and regulating the composition and dosage of the electrolyte, the decomposition of the lithium salt can be effectively inhibited, while avoiding the increase of impedance, improving the stability of the battery under high temperature and high pressure, and improving the safety performance and cycle performance of the battery. Specifically, in the present application, the primer layer can significantly improve the needle puncture safety performance, but under high temperature and high pressure, the Al-OH group on the surface of the coating component (boehmite, gibbsite or pseudo-boehmite) will react with LiPF6 or its hydrolysis intermediate (such as: PF5 or POF3) to release HF, and the coating component further releases H2O by reacting with HF, and the trace amount of physically adsorbed water or structural water that the coating component itself may contain will also release H2O under high temperature and high pressure, and then form a vicious cycle of "water-aggravated LiPF6 decomposition → acid production → solvent decomposition or other reactions → water production", while accelerating the dissolution of transition metals, and the cycle life and safety performance are poor. The present application uses dinitrile and HTCN in the electrolyte, in which the cyano group reacts with PF6 - Can form a stable complex to prevent PF6 -It decomposes into PF5, inhibiting the reaction of LiPF6 and its hydrolysis intermediate PF5 with substances in the primer layer to generate HF; the electrical conductivity of compound I is relatively high, which is conducive to desolvation, and can improve the impedance increased by the use of nitrile substances. In addition, compound I can optimize the SEI film, and the fluorinated layer generated on the surface of the negative electrode can inhibit the reduction of nitrile substances at the negative electrode and inhibit their corrosion to the negative electrode.

[0052] The present application limits the relationship between the content of LiPF6 and nitrile substances, which can achieve a balance between impedance and high-temperature and high-pressure stability. If (B+C) / A is higher than 0.6, that is, the lithium salt concentration is insufficient, resulting in increased interface impedance, nitrile destroys the uniformity of the SEI film and the impedance is large; when (B+C) / A is lower than 0.07, that is, when the lithium salt concentration is too high and the nitrile is insufficient, LiPF6 hydrolysis is accelerated to produce HF, resulting in electrode corrosion, poor high-temperature performance, and reduced safety performance; the present application limits the lithium salt concentration, which can ensure sufficient Li+ concentration to maintain conductivity and prevent excessive LiPF6 concentration from increasing viscosity and affecting wettability, thereby increasing the risk of hydrolysis; by limiting the dinitrile content, it can ensure that the lithium ion concentration is consistent with PF6. - The HTCN structure can provide more coordination sites, and its content within the above range can cooperate with dinitrile to stabilize PF6 - , to prevent high impedance. However, if B<0.5%, C<0.5%, even if (B+C) / A>0.07, it will still cause PF6 - Insufficient stability accelerates LiPF6 decomposition. If B > 3.5% and C > 3.5%, even if (B + C) / A < 0.6, the lithium salt content is too high, resulting in high impedance and deteriorating low-temperature performance. By selecting dinitriles, the problems of short carbon chains prone to gas decomposition and long carbon chains with high impedance can be avoided. HTCN, compared to other trinitriles, coordinates better with lithium salts and has lower impedance, thus ensuring comprehensive battery performance.

[0053] In the present application, the preparation method of the base coating may include the following steps: mixing boehmite powder or gibbsite or pseudo-boehmite with a binder (PVDF) in a mass ratio, wherein the mass proportion of the binder in the base coating is 2 to 10%; using NMP or deionized water as a solvent to prepare a slurry with a solid content of 30-50%; applying it on an aluminum foil current collector by micro-gravure coating or slit coating; and drying in stages: initial drying at 80-100°C for 10-30 minutes, and then curing at 120-150°C for 1-2 hours.

[0054] In some optional embodiments, B, C, and D satisfy: 0.7≤D / (B+C)≤10; as an example, the value of D / (B+C) can be 0.7, 1, 2, 4, 5, 6, 8, 10, or within the range of any of the above values.

[0055] By limiting the content relationship between compound I and nitrile compounds, the present application can avoid the insufficiency of the stability of the LiF-rich film formed at the electrode interface and the insufficiency of the desolvation promotion when D / (B+C)<0.7, resulting in the Li + The solvation energy barrier is high, which affects the low-temperature performance; when D / (B+C)>10, the electrolyte impedance increases and the mechanical strength of the SEI film weakens, affecting the further improvement of the battery's high-temperature performance and safety performance.

[0056] In some optional embodiments, the thickness of the primer layer is T μm, 0.5≤T≤5; as an example, the thickness of the primer layer can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, or within a range consisting of any of the above values.

[0057] This application achieves a balance between safety and electrical performance by limiting the thickness of the primer layer. If the primer layer is too thin, uneven thickness can occur, leading to increased local acid production, instability at the positive electrode interface, and little improvement in needle puncture safety. Increasing the thickness improves needle puncture safety and reduces interfacial side reactions, but excessively thick primer layers can increase internal stress, leading to interfacial delamination, increased impedance, and reduced battery energy density.

[0058] In some optional embodiments, D and T satisfy: 1≤D / T≤10. As an example, the ratio D / T between the content of the compound I and the thickness of the primer layer can be 1, 3, 4, 5, 6, 7, 8, 9, 10, or within a range consisting of any of the above values.

[0059] It will be understood by those skilled in the art that the thicker the primer layer, the higher the safety, the greater the impact on impedance, and the more compound I needs to be added to improve the kinetics. However, if the content of compound I is too high, it will affect the high-temperature performance. When D and T satisfy the relationship, the effect can be optimized. When D / T <1, the kinetic performance deteriorates. When D / T > 10, it will have a certain impact on the high-temperature performance.

[0060] In some optional embodiments, the electrolyte further includes a compound II with a mass percentage of E%, 10≤E≤60; and the compound II includes at least one of propyl propionate (PP) and ethyl butyrate (EB).

[0061] As an example, the mass percentage of the compound II can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, or within the range of any of the above values. In the present application, the carboxylic acid ester solvent in the compound II has a high boiling point and flash point, which can significantly improve the thermal stability of the electrolyte, especially compensate for the shortcomings of the poor performance of the compound I at high temperatures, and further improve the safety performance.

[0062] In some optional embodiments, the electrolyte further includes 0.01%-2% lithium difluorophosphate; as an example, the content of the lithium difluorophosphate can be 0.01%, 0.05%, 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.7%, 2%, or within a range consisting of any of the above values.

[0063] In this application, the use of lithium difluorophosphate (LiPO2F2) can further improve the interface stability. If the content is too low, the film-forming effect is insufficient and the interface effect cannot be improved. If the content is too high, its solubility will be problematic and the impedance will increase.

[0064] In some optional embodiments, the electrolyte further comprises 2%-30% by weight of fluoroethylene carbonate (FEC), and / or 0.5%-6% by weight of 1,3-propane sultone (PS).

[0065] In this application, the use of fluoroethylene carbonate and 1,3-propane sultone can improve negative electrode interface issues and further enhance cycling and high-temperature stability. A low FEC content can lead to insufficient film formation, while a high content can easily generate gas and affect safety. A low PS content can lead to insufficient film formation, while a high content can increase impedance and poor low-temperature performance.

[0066] In some optional embodiments, the surface of the negative electrode sheet is provided with grooves, the depth of the grooves is 3μm-45μm, the width is 30μm-300μm, and the spacing is 0.2mm-10mm; as an example, the depth of the grooves can be 3μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, or within the range of any of the above values; the width of the grooves can be 30μm, 50μm, 80μm, 100μm, 150μm, 200μm, 250μm, 300μm, or within the range of any of the above values; the spacing of the grooves can be 0.2mm, 0.5mm, 1mm, 2mm, 4mm, 5mm, 6mm, 8mm, 10mm, or within the range of any of the above values.

[0067] It will be understood by those skilled in the art that the provision of an undercoat layer and the use of nitrile substances in the electrolyte will hinder the transmission of lithium ions. The present application increases the electrolyte wetting performance and improves the lithium ion transmission dynamics by providing grooves in the negative electrode sheet, thereby compensating for the increase in impedance that may be caused by the use of the undercoat layer and nitrile substances, and at the same time, improves the heat dissipation effect. By limiting the depth of the groove to the above range, the present application can ensure that the electrolyte fully infiltrates the negative electrode active material, while reserving expansion space and being able to adapt to high surface capacity electrodes; if the groove depth is less than 3μm: the infiltration improvement is not obvious, the local current density is too high, the risk of lithium plating increases, and the kinetic performance is affected; the groove depth is greater than 45μm: the mechanical strength of the current collector decreases, the risk of electrode fracture increases, and the safety performance deteriorates; the groove width is within the above range, which can ensure the improvement of the effective specific surface area while taking into account the lateral diffusion of lithium ions and the active material load; if the groove width is less than 30μm: processing is difficult; the groove width is less than 300μm: the capacity of the active material is reduced; the groove spacing is within the above range, which can shorten the lateral diffusion distance of lithium ions, reduce impedance, and have good dynamics; if the groove spacing is less than 0.2mm: the structural strength decreases, and the risk of cracking during coating is aggravated; the groove spacing is greater than 10mm: the electrolyte concentration gradient increases and the impedance increases.

[0068] Optionally, the groove is at least one of a linear groove, a grid groove, a wavy groove, an annular groove, a lattice groove, a spiral groove, a cross groove or a zigzag groove. In this application, the preparation of the groove is conventional in the field. As an example, a linear groove structure can be formed by laser wire-punching technology.

[0069] In some optional embodiments, the length of the positive electrode active layer is L1, and the area 30% L1 to 70% L1 from the starting end is the middle area, and a first electrode tab groove is provided in the middle area, and a positive electrode tab is provided in the first electrode tab groove;

[0070] And / or, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side surface of the current collector, the length of the negative electrode active layer is L2, the area 30% L2 to 70% L2 from the starting end is the middle area, a second electrode tab groove is provided in the middle area, and a negative electrode tab is provided in the second electrode tab groove.

[0071] In this application, a central tab structure is adopted, which reduces the redundant space of the tab bending and end stacking, making the internal structure of the battery cell more compact, compensating for the volume energy density (ED) loss caused by the bottom coating setting, reducing internal resistance, improving charging and discharging efficiency, and accelerating heat dissipation.

[0072] In some optional embodiments, the negative electrode active layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the mass percentage of silicon element is 1.5%-50% based on the total mass of the negative electrode active layer, and the Dv50 particle size of the silicon-based material is 5-15 μm; as an example, the mass percentage of silicon element in the negative electrode active layer can be 1.5%, 5%, 10%, 15%, 20%, 25%, 30%, 40%, 50%, or within a range consisting of any of the above values; the particle size can be 5 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 15 μm, or within a range consisting of any of the above values;

[0073] Preferably, the mass percentage of compound I in the electrolyte is 3%-15%;

[0074] Preferably, the mass percentage of the fluoroethylene carbonate is 12%-30%.

[0075] It is understood by those skilled in the art that silicon-based materials can improve energy density compared to carbon-based materials, but there is a large volume expansion during the charge and discharge process, which leads to repeated rupture and regeneration of the solid electrolyte interface (SEI) film, consumption of active lithium and electrolyte, and ultimately leads to battery capacity decay. If the silicon content is less than 1.5%, the capacity improvement is not significant and the silicon-based advantages cannot be reflected. If the silicon content is greater than 50%, the volume expansion is uncontrollable and prone to cracking, leading to continuous regeneration of SEI and consumption of electrolyte. If the particle size of the silicon-based material is less than 5μm, the specific surface area is too large, resulting in aggravated interface side reactions and poor safety performance. If the particle size of the silicon-based material is greater than 15μm, the lithium ion diffusion kinetics deteriorate and the kinetics deteriorate, leading to capacity decay.

[0076] In the electrolyte of the present application, FEC can continuously repair the negative electrode SEI film. Therefore, when the negative electrode active material includes a silicon-based material, the amount of compound I is appropriately reduced and / or the amount of FEC is increased to improve the silicon negative electrode interface and alleviate the adverse effects of silicon expansion.

[0077] In some optional embodiments, the primer layer covers the entire area of ​​both side surfaces of the positive electrode current collector.

[0078] Those skilled in the art will understand that in silicon-based anode batteries, the expansion of the silicon-based material can easily lead to fractures at the interface between the tail current collector and the active layer. The continuous application of the primer layer can increase ductility, inhibit fractures, and further enhance needle puncture safety. This design also prevents electrolyte corrosion at the edges of the current collector.

[0079] In some optional embodiments, the positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide.

[0080] According to another aspect of the present application, there is also provided an electrical device comprising the above-mentioned lithium-ion battery.

[0081] The electrical equipment provided in this application has the same advantages as the above-mentioned lithium-ion batteries due to the use of the lithium-ion batteries provided in this application, which will not be described in detail here.

[0082] Those skilled in the art will appreciate that the lithium-ion battery provided herein also includes structural components such as a diaphragm and a housing. During the battery's charge and discharge process, lithium ions are intercalated and released back and forth between the positive and negative electrodes. The electrolyte acts as an ion conductor between the positive and negative electrodes. The diaphragm, disposed between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing lithium ions to pass through.

[0083] As an example, the materials, composition, and manufacturing method of the positive electrode sheet used in the lithium-ion battery of the present application may include any technology disclosed in the prior art. For example, the positive electrode active layer includes a positive electrode active material, a conductive agent, and a binder. In terms of mass percentage, the positive electrode active layer includes 80% to 99.8% of the positive electrode active material, 0.1% to 10% of the conductive agent, and 0.1% to 10% of the binder. Preferably, it includes 90% to 99.6% of the positive electrode active material, 0.2% to 5% of the conductive agent, and 0.2% to 5% of the binder.

[0084] The types of positive electrode active materials in the present invention include lithium cobalt oxide materials and may also include ternary positive electrode materials and the like.

[0085] The present invention does not particularly limit the conductive agent in the positive electrode sheet, which can be selected from conductive agents commonly used in the art, including but not limited to one or more of acetylene black, conductive carbon black, Ketjen black, conductive graphite, carbon nanotubes, conductive carbon fibers, and graphene.

[0086] The present invention does not particularly limit the binder in the positive electrode sheet, which can be selected from binders commonly used in the art, including but not limited to one or more of polyvinylidene fluoride, polytetrafluoroethylene, sodium carboxymethyl cellulose, styrene-butadiene rubber, and polyethylene oxide.

[0087] As an example, the materials, composition, and manufacturing method of the negative electrode sheet used in the lithium-ion battery of the present application may include any technology disclosed in the prior art. For example, the negative electrode active layer includes a negative electrode active material, a conductive agent, and a binder. According to the battery of the present invention, the negative electrode active material is selected from conventional graphite and / or silicon materials. The negative electrode active layer includes, by weight percentage, 80-98.5% of the negative electrode active material, 0.1-10% of the conductive agent, and 0.1-10% of the binder.

[0088] According to the battery of the present invention, there is no particular limitation on the types of the conductive agent and binder in the negative electrode sheet. The selection range can refer to the types of the conductive agent and binder in the positive electrode sheet, and will not be repeated here.

[0089] The material and shape of the separator used in the lithium-ion battery of the present application are not particularly limited, and may include any technology disclosed in the prior art. As an example, one of conventional polyethylene (PE), polypropylene (PP), PP and PE composite separators.

[0090] The electrolyte used in the lithium-ion battery of the present application may also include any technology disclosed in the prior art. The electrolyte used in the present application is a non-aqueous electrolyte. In addition to the above-mentioned dinitrile, trinitrile, 2,2-difluoroethyl acetate, ethyl 2,2-difluoroacetate, propyl propionate (PP), ethyl butyrate (EB), lithium hexafluorophosphate, FEC, and PS, the electrolyte may also include other organic solvents, other lithium salts, or other functional additives.

[0091] Among them, other organic solvents can be selected from carbonate solvents and / or carboxylate solvents, carbonate solvents can be selected from ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC) and one or more fluorinated solvents of the above solvents, and carboxylate solvents can be selected from ethyl acetate (EA), propyl acetate, n-butyl acetate, isobutyl acetate, methyl propionate (MP), ethyl propionate (EP), methyl butyrate and one or more fluorinated solvents of the above solvents.

[0092] Other additives include one or more of vinylene carbonate (VC), vinyl ethylene carbonate (VEC), tetravinylsilane (TVS), tris(trimethylsilyl)borate (TMSB), hexamethyldisilazane (HMDS), fluorobenzene (FB), triphenyl phosphite (TPPi), benzonitrile, p-toluonitrile, 3,5-difluorobenzonitrile, glutaronitrile, suberonitrile, ethylene glycol bis(propionitrile) ether, glycerol trinitrile, tris(2-cyanoethyl) phosphate, ethoxy(pentafluoro)cyclotriphosphazene (PFPN), pentafluoro(phenoxy)cyclotriphosphazene and other phosphorus-containing trinitriles.

[0093] Other lithium salts may be selected from electrolyte lithium salts conventionally used in the art, including but not limited to lithium tetrafluoroborate (LiBF4), lithium bis(trifluoromethylsulfonyl imide) (LiTFSI), lithium difluorooxalatoborate (LiDFOB), lithium bis(oxalatoborate) (LiBOB), lithium bis(fluorosulfonyl imide) (LiFSI), lithium 4,5-dicyano-2-trifluoromethylimidazole (LiDTI), lithium difluorobis(oxalatophosphate), lithium hexafluorozirconate (LiZrF6), and lithium trifluoromethylsulfinate (LiCF3SO3). One or more.

[0094] The present application does not specifically limit the preparation method of the lithium-ion secondary battery, and the lithium-ion secondary battery can be prepared using conventional preparation methods in the art. For example, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in sequence, with the separator positioned between the positive and negative electrode sheets, and a battery cell is obtained by stacking or winding the sheets. The battery cell is then baked, injected, formed, and packaged to obtain the lithium-ion secondary battery of the present application.

[0095] It is understood that in the electrical equipment provided herein, the lithium-ion secondary battery can be used as a power source for the electrical equipment or as an energy storage unit for the electrical equipment. The electrical equipment may include, but is not limited to, mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0096] The present application will be described below with reference to specific examples. It should be noted that these examples are merely descriptive and do not limit the present application in any way. In the examples, if no specific experimental steps or conditions are indicated, the operation or conditions of the conventional experimental steps described in the literature in this area can be carried out. If the manufacturer is not indicated for reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0097] Example 1

[0098] This embodiment provides a lithium-ion battery, the specific composition and preparation method of which are as follows:

[0099] 1) Preparation of positive electrode sheet: The structural diagram of the positive electrode sheet is as follows Figure 1 As shown, the positive electrode current collector 3 includes a bottom coating 1 and a positive electrode active layer 2 arranged in sequence on both sides. The left side of the figure is the starting end of the winding. The preparation method includes: the positive electrode active material LiCoO2, the conductive agent carbon black, and the binder polyvinylidene fluoride are dispersed in N-methylpyrrolidone according to a mass ratio of 96.8:2.0:1.2, and are fully stirred to form a uniform positive electrode slurry. The positive electrode slurry is coated on the safe boehmite bottom coating (thickness 2.5 microns), and the positive electrode sheet is obtained after drying, rolling, and cutting; compacting 4.2g / cm 3 ;

[0100] 2) Preparation of negative electrode sheet: Weigh the negative electrode active material (artificial graphite, particle size Dv50 is 4.5μm), conductive agent carbon black, binder styrene butadiene rubber, and thickener sodium carboxymethyl cellulose in a weight ratio of 97.2:0.5:1.0:1.3, disperse them in an appropriate amount of deionized water, stir thoroughly to form a uniform negative electrode slurry, and coat the negative electrode slurry on the negative electrode current collector copper foil, then dry, roll press, and cut to obtain the negative electrode sheet; compaction 1.6g / cm3 ;

[0101] 3) Preparation of electrolyte: In an argon-filled glove box (H2O <0.1ppm, O2 <0.1ppm), EC / PC / EP were mixed in a mass ratio of 10:15:15, and then 26wt% DFEA and 5wt% PP based on the total mass of the electrolyte were added, followed by 14% of fully dried lithium hexafluorophosphate (LiPF6). After dissolution, 0wt% FEC, 0.5wt% SN, 0.5wt% ADN, 2wt% HTCN, 0wt% PS, 0wt% PST, 0wt% LiODFB, and 0wt% LiPO2F2 based on the total mass of the electrolyte were added and stirred evenly. After passing the moisture and free acid tests, the desired non-aqueous electrolyte was obtained;

[0102] 4) Diaphragm: PE porous polymer film is used as the diaphragm;

[0103] 5) Assembly of lithium-ion batteries: The positive electrode sheet, negative electrode sheet, and separator are placed in order, with the separator located between the positive and negative electrode sheets. The tabs are then welded (the tabs are located on the edge of the electrode sheet) and wound to obtain a core. The core is then placed in an aluminum-plastic film packaging bag. Liquid injection, formation, secondary sealing, and sorting are then performed to prepare a 4500mAh lithium-ion battery (664863R).

[0104] Example 2-Example 10

[0105] Compared with Example 1, the differences are: the composition of the electrolyte, the thickness of the primer layer, the setting of the negative electrode groove, the position of the tab, etc. Among them, Example 9 adopts a central tab structure, and the position of the tab is the same as that of Example 11 below. Other differences are detailed in Table 1.

[0106] Example 11

[0107] This embodiment provides a lithium-ion battery, the specific composition and preparation method of which are as follows:

[0108] 1) Preparation of positive electrode sheet: The structural diagram of the positive electrode sheet is as follows Figure 1 As shown, the two sides of the positive electrode current collector 3 include a primer layer 1 and a positive electrode active layer 2 arranged in sequence. The left side of the figure is the starting end of the winding. The preparation method includes: the positive electrode active material LiCoO2, the conductive agent carbon black, and the binder polyvinylidene fluoride are dispersed in N-methylpyrrolidone according to a mass ratio of 96.8:2.0:1.2, and are fully stirred to form a uniform positive electrode slurry. The positive electrode slurry is coated on a safe boehmite primer layer (thickness 2.5 microns, the mass ratio of boehmite powder to binder (PVDF) is 15:1), and the positive electrode sheet is obtained after drying, rolling, and cutting; compaction 4.2g / cm 3 ;

[0109] 2) Preparation of negative electrode sheet: Weigh the negative electrode active material (artificial graphite and silicon, with a silicon particle size Dv50 of 9 μm, where the silicon content accounts for 12% of the negative electrode active layer), conductive agent carbon black, binder styrene-butadiene rubber, and thickener sodium carboxymethyl cellulose in a weight ratio of 97.2:0.5:1.0:1.3, disperse them in an appropriate amount of deionized water, stir thoroughly to form a uniform negative electrode slurry, and coat the negative electrode slurry on the negative electrode current collector copper foil, then dry, roll-press, and cut to obtain the negative electrode sheet; compact 1.75 g / cm 3 , a linear groove structure is formed by laser marking technology, wherein the groove has a depth of 10 μm, a width of 150 μm and a spacing of 2 mm;

[0110] 3) Preparation of electrolyte: In an argon-filled glove box (H2O <0.1ppm, O2 <0.1ppm), EC / PC / EP were mixed in a mass ratio of 10:15:15, and then 13wt% DFEA and 26.1wt% PP based on the total mass of the electrolyte were added, and then 14% of fully dried lithium hexafluorophosphate (LiPF6) was added. After dissolution, 14wt% FEC, 1wt% SN, 1wt% ADN, 2wt% HTCN, 2wt% PS, 0.2wt% 1,3-propylene sulfone PST, 0.3wt% LiODFB, and 0.2wt% LiPO2F2 based on the total mass of the electrolyte were added and stirred evenly. After passing the moisture and free acid tests, the desired non-aqueous electrolyte was obtained;

[0111] 4) Diaphragm: PE porous polymer film is used as the diaphragm;

[0112] 5) Assembly of lithium-ion batteries: The positive electrode sheet, negative electrode sheet and separator are placed in order, with the separator located between the positive and negative electrode sheets. The electrodes are then welded together (the electrodes are drawn out from the positive and negative electrodes at 1 / 2 of the middle layer at the starting end of the winding to ensure a balanced bidirectional current transmission path) and wound to obtain a core. The core is then placed in an aluminum-plastic film packaging bag. The process includes liquid injection, formation, secondary sealing, and sorting to prepare a 4500mAh lithium-ion battery (664863R). The electrical performance of the battery is then tested.

[0113] Example 12-Example 45

[0114] Compared with Example 11, the differences are: the composition of the electrolyte, the thickness of the primer layer, the setting of the negative electrode groove, the position of the electrode tab, etc., see Table 1 for details.

[0115] Table 1

[0116]

[0117]

[0118] Comparative Example 1

[0119] This comparative example provides a lithium ion battery, which is different from Example 2 in that it does not include a primer layer.

[0120] Comparative Example 2

[0121] This comparative example provides a lithium ion battery. Compared with Example 2, the difference is that the composition of the primer layer is different, and alumina is used instead of boehmite.

[0122] Comparative Example 3

[0123] This comparative example provides a lithium-ion battery. Compared with Example 2, the difference is that the composition of the electrolyte is different and does not contain SN and ADN.

[0124] Comparative Example 4

[0125] This comparative example provides a lithium-ion battery, which is different from Example 2 in that the composition of the electrolyte is different and does not contain HTCN.

[0126] Comparative Example 5

[0127] This comparative example provides a lithium ion battery. Compared with Example 2, the difference lies in that the composition of the electrolyte is different, the content of SN is 0.1%, and the content of ADN is 0.1%.

[0128] Comparative Example 6

[0129] This comparative example provides a lithium ion battery. Compared with Example 2, the difference lies in that the composition of the electrolyte is different and the content of HTCN is 0.2%.

[0130] Comparative Example 7

[0131] This comparative example provides a lithium-ion battery. Compared with Example 2, the difference is that the composition of the electrolyte is different, the content of LiPF6 is 16%, the content of SN is 0.25%, the content of ADN is 0.25%, and the content of HTCN is 0.5%.

[0132] Comparative Example 8

[0133] This comparative example provides a lithium ion battery. Compared with Example 2, the difference is that the composition of the electrolyte is different and the content of DFEA is 1%.

[0134] Test Case

[0135] The lithium-ion batteries provided in each embodiment and comparative example were subjected to performance tests. The specific test items and methods are as follows:

[0136] 1. Cycle performance test: Place the lithium-ion battery in a 45°C environment and let it stand for 2 hours. When the battery temperature is 45±2°C, charge it to the upper limit voltage (4.53V) at a constant current of 1C, let it stand for 5 minutes and measure the thickness as H0. Then discharge it to 3.0V at a constant current of 0.5C and let it stand for 5 minutes. This is one charge and discharge cycle. The charge and discharge cycle is 500 times. The highest discharge capacity of the first three cycles is recorded as the initial capacity Q0, the discharge capacity of the 500th cycle is Q1, and the thickness after the battery is fully charged is H1. Calculate the battery capacity retention rate = Q1 / Q0×100%; thickness change rate = H1 / H0×100%;

[0137] 2. 130°C thermal shock test: The above-mentioned lithium-ion battery is subjected to a 130°C thermal shock test. The test process is as follows: first, the battery is charged at a constant current and constant voltage of 0.7C to an upper limit voltage of 4.53V and a cut-off current of 0.05C; then the above-mentioned battery is placed in a convection or circulating hot air oven, heated at an initial temperature of 25±3°C, a heating rate of 5±2°C, and the temperature is raised to 130±2°C and maintained for 60 minutes before the test is completed. The passing standard of the 130°C thermal shock test is: the battery cell does not catch fire or explode. 15 samples are tested for each embodiment or comparative example, and the number of batteries that pass the test, N, is recorded, and recorded as N / 15.

[0138] The specific test results are shown in the table below:

[0139] Table 2

[0140]

[0141]

[0142]

[0143] It can be seen from the test results in the above table that the embodiments of the present application can effectively inhibit the decomposition of lithium salts by providing a primer layer in the positive electrode sheet and regulating the composition and dosage of the electrolyte, while avoiding the increase in impedance, improving the stability of the battery under high temperature and high pressure, and enhancing the safety performance and cycle performance of the battery.

[0144] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A lithium-ion battery, characterized in that: include: Positive electrode, negative electrode and electrolyte, The positive electrode sheet comprises a positive electrode current collector and a primer layer located on at least one side of the positive electrode current collector, wherein a positive electrode active layer is provided on a surface of the primer layer away from the positive electrode current collector; The primer layer includes at least one of boehmite, gibbsite, and pseudo-boehmite; Based on the total mass of the electrolyte, it includes A% LiPF6, B% dinitrile, C% 1,3,6-hexanetrinitrile, and D% compound I, wherein the dinitrile includes succinonitrile and / or adiponitrile, and the compound I includes at least one of 2,2-difluoroethyl acetate and ethyl 2,2-difluoroacetate; Moreover, A, B, C, and D satisfy: 10≤A≤20, 0.5≤B≤3.5, 0.5≤C≤3.5, 3≤D≤30, 0.07≤(B+C) / A≤0.

6.

2. The lithium-ion battery according to claim 1, wherein The B, C, and D satisfy the following conditions: 0.7≤D / (B+C)≤10; and / or, the thickness of the primer layer is T μm, 0.5≤T≤5; Preferably, D and T satisfy: 1≤D / T≤10.

3. The lithium-ion battery according to claim 1, wherein The electrolyte further comprises compound II in a mass percentage of E%, 10≤E≤60; The compound II includes at least one of propyl propionate and ethyl butyrate.

4. The lithium-ion battery according to claim 1, wherein The electrolyte also includes 0.01%-2% lithium difluorophosphate; And / or, the electrolyte further comprises 2% to 30% by weight of fluoroethylene carbonate; And / or, the electrolyte further comprises 0.5%-6% by mass of 1,3-propane sultone.

5. The lithium-ion battery according to any one of claims 1 to 4, characterized in that: The surface of the negative electrode sheet is provided with grooves, the depth of the grooves is 3 μm-45 μm, the width is 30 μm-300 μm, and the spacing is 0.2 mm-10 mm; Preferably, the groove is at least one of a linear groove, a grid-shaped groove, a wavy groove, an annular groove, a lattice groove, a spiral groove, a cross groove or a serrated groove.

6. The lithium-ion battery according to any one of claims 1 to 4, characterized in that: The length of the positive electrode active layer is L1, and the area 30% L1 to 70% L1 from the starting end of the positive electrode active layer is the middle area. A first electrode tab groove is provided in the middle area, and a positive electrode tab is provided in the first electrode tab groove; And / or, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer located on at least one side of the current collector, the length of the negative electrode active layer is L2, the area 30% L2 to 70% L2 away from the starting end of the positive electrode active layer is the middle area, a second electrode tab groove is provided in the middle area, and a negative electrode tab is provided in the second electrode tab groove.

7. The lithium-ion battery according to claim 6, characterized in that The negative electrode active layer includes a negative electrode active material, the negative electrode active material includes a silicon-based material, the mass percentage of silicon element is 1.5%-50% based on the total mass of the negative electrode active layer, and the Dv50 particle size of the silicon-based material is 5-15 μm; Preferably, the mass percentage of compound I in the electrolyte is 3%-15%; Preferably, the mass percentage of the fluoroethylene carbonate is 12%-30%.

8. The lithium-ion battery according to claim 7, characterized in that The primer layer covers the entire area of ​​both side surfaces of the positive electrode current collector.

9. The lithium-ion battery according to claim 7, characterized in that The positive electrode active layer includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide.

10. An electrical device, characterized in that: A lithium-ion battery comprising the lithium-ion battery according to any one of claims 1 to 9.

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