Electrolyte, battery and electric device

Abstract

The embodiment of the invention provides an electrolyte, a battery and a power utilization device, and relates to the field of batteries. The electrolyte comprises a solvent and an electrolyte additive, the solvent comprises an oxidation-resistant solvent, and the oxidation voltage of the oxidation-resistant solvent is greater than 5V; the electrolyte additive comprises vinylene carbonate. According to the electrolyte, the battery and the electric device provided by the embodiment of the invention, the first coulombic efficiency and the cycle performance of the battery can be improved.

Description

Technical Field

[0001] The present application relates to the field of batteries, and in particular to an electrolyte, a battery and an electrical device. Background Art

[0002] At present, increasing the working voltage of the battery is one of the effective ways to increase the energy density. However, as the working voltage of the battery increases, the electrolyte will intensify the oxidative decomposition. In order to improve the oxidation resistance of the electrolyte, compounds with higher oxidation voltage are often added as co-solvents to improve the oxidation resistance of the electrolyte, but this often causes a significant decrease in the first coulombic efficiency of the battery and a decrease in the cycle performance. Summary of the invention

[0003] In view of the above problems, the present application provides an electrolyte, a battery and an electrical device, which can improve the initial coulombic efficiency and cycle performance of the battery.

[0004] In a first aspect, the present application provides an electrolyte, comprising a solvent and an electrolyte additive, wherein the solvent comprises an oxidation-resistant solvent, and the oxidation voltage of the oxidation-resistant solvent is greater than 5V; and the electrolyte additive comprises polyvinyl carbonate.

[0005] In the technical solution of the embodiment of the present application, the electrolyte contains both an oxidation-resistant solvent and polyvinyl carbonate, which can reduce the side reaction between the oxidation-resistant solvent and the negative electrode while increasing the oxidation decomposition voltage of the electrolyte, thereby improving the battery's cycling and storage performance at high voltage. The electrolyte contains an oxidation-resistant solvent, which can improve the oxidation resistance of the electrolyte and stabilize the interface between the positive electrode and the electrolyte; at the same time, the electrolyte also contains polyvinyl carbonate, which can coat the surface of the negative electrode with an organic film before the oxidation-resistant solvent reacts with the negative electrode to improve the compatibility between the oxidation-resistant solvent and the negative electrode, thereby improving the battery's first coulombic efficiency and cycling performance.

[0006] In some embodiments, the oxidation-resistant solvent includes one or more of sulfone organic solvents and nitrile organic solvents; optionally, the oxidation-resistant solvent includes one or more of ethyl methyl sulfone, methoxyethyl methyl sulfone, tetramethyl sulfone, adiponitrile, glutaronitrile and sebaconitrile. Sulfone organic solvents and nitrile organic solvents have oxidation resistance characteristics and are suitable as oxidation-resistant solvents.

[0007] In some embodiments, the mass ratio of the polyvinylene carbonate to the oxidation-resistant solvent is 0.1%: 1 to 10%: 1, and can be optionally 0.5%: 1 to 3%: 1. The polyvinylene carbonate and the oxidation-resistant solvent work together to improve the compatibility of the oxidation-resistant solvent and the negative electrode, so that the oxidation-resistant solvent plays a positive role.

[0008] In some embodiments, the oxidation-resistant solvent in the electrolyte accounts for 10% to 30% by mass; and the polyvinylene carbonate in the electrolyte accounts for 0.05% to 3% by mass.

[0009] In some embodiments, the electrolyte additive further comprises a coupling agent; optionally, the coupling agent comprises one or more of a silane coupling agent and a titanate coupling agent. The coupling agent can make the combination of polyvinylene carbonate and the negative electrode more firmly.

[0010] In some embodiments, the mass ratio of the polyvinylene carbonate to the coupling agent in the electrolyte is 1%:1 to 10%:1.

[0011] In some embodiments, the solvent also includes an organic solvent, and the organic solvent includes one or more of a carbonate solvent, a carboxylate solvent, and an ether solvent; optionally, the organic solvent also includes one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, and propylene carbonate.

[0012] In some embodiments, the mass ratio of the oxidation-resistant solvent to the organic solvent is 1:9 to 9:9, and can be optionally 1:9 to 3:9.

[0013] In some embodiments, the polyvinylene carbonate is distributed in the electrolyte in the form of particles; the molecular weight of the polyvinylene carbonate is 10,000 to 200,000, and the true density of the polyvinylene carbonate particles is 0.9 to 1.1 g / cm 3 The polyvinyl carbonate particles are dispersed in the electrolyte and tend to have a certain affinity with the negative electrode.

[0014] In a second aspect, the present application provides a battery, comprising the electrolyte of the aforementioned embodiment.

[0015] In some embodiments, a negative electrode plate is also included, and polyvinyl carbonate is adsorbed on the surface of the negative electrode plate.

[0016] In some embodiments, a negative electrode plate is also included, and a coupling agent is adsorbed on the surface of the negative electrode plate.

[0017] In a third aspect, the present application provides an electrical device, comprising the battery of the aforementioned embodiment.

[0018] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present application. Moreover, the same reference numerals are used throughout the drawings to represent the same components. In the drawings:

[0020] Figure 1 A schematic diagram of the structure of a vehicle according to some embodiments of the present application;

[0021] Figure 2 A schematic diagram of the exploded structure of a battery according to some embodiments of the present application;

[0022] Figure 3 A schematic diagram of the structure of a battery cell provided in some embodiments of the present application;

[0023] Figure 4 This is a schematic diagram of the exploded structure of a battery cell according to some embodiments of the present application.

[0024] Icons: 1000-vehicle; 100-battery; 10-casing; 11-accommodating space; 12-first part; 13-second part; 20-battery cell; 21-casing; 211-opening; 22-end cover assembly; 221-end cover; 222-electrode terminal; 23-electrode assembly; 24-current collecting member; 25-insulating protection member; 200-controller; 300-motor. DETAILED DESCRIPTION

[0025] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0027] In the description of the embodiments of the present application, the technical terms "first", "second", etc. 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. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0028] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0029] In the description of the embodiments of the present application, the term "plurality" refers to more than two (including two), and similarly.

[0030] In the description of the embodiments of the present application, the orientations or positional relationships indicated by technical terms such as "thickness", "up", "down", "front", "back", "top", "bottom", "inside", and "outside" are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the embodiments of the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the embodiments of the present application.

[0031] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, technical terms such as "installation", "connection", "fixation" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present application can be understood according to the specific circumstances.

[0032] At present, judging from the development of the market situation, the application of power batteries is becoming more and more extensive. Power batteries are not only used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, but also widely used in electric vehicles such as electric bicycles, electric motorcycles, electric vehicles, as well as military equipment and aerospace and other fields. With the continuous expansion of the application field of power batteries, the market demand is also constantly expanding. Existing power batteries are mainly metal ion batteries. For example, lithium ion batteries have the characteristics of high energy density and long life, which are suitable for use as power batteries.

[0033] Increasing the operating voltage of a battery is an effective way to increase its energy density. However, as the operating voltage of the battery increases, the oxidation decomposition of the electrolyte will intensify. In order to improve the oxidation resistance of the electrolyte, compounds with higher oxidation voltages are often introduced as co-solvents. However, such compounds usually have poor compatibility with negative electrode materials, which can lead to structural damage to the negative electrode material and a significant reduction in the first coulombic efficiency of the battery.

[0034] In order to solve the problem that conventional additives are difficult to truly improve the compatibility between the oxidation-resistant group and the negative electrode, an electrolyte can be designed, which contains an oxidation-resistant solvent and polyvinyl carbonate. Before the oxidation-resistant solvent reacts with the negative electrode, polyvinyl carbonate can be preferentially adsorbed on the surface of the negative electrode to form an organic film, thereby truly and effectively improving the compatibility problem between the oxidation-resistant solvent and the negative electrode, thereby improving the battery's first coulombic efficiency and cycle performance.

[0035] The embodiment of the present application provides an electric device using a battery as a power source, and the electric device may be, but is not limited to, a mobile phone, a tablet, a laptop, an electric toy, an electric tool, a battery car, an electric car, a ship, a spacecraft, etc. Among them, the electric toy may include a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy, and an electric airplane toy, etc., and the spacecraft may include an airplane, a rocket, a space shuttle, and a spacecraft, etc.

[0036] For the convenience of description, the following embodiments are described by taking a vehicle 1000 as an example of an electrical device according to an embodiment of the present application.

[0037] Please refer to Figure 1 , Figure 1 The schematic diagram of the structure of the vehicle 1000 provided in some embodiments of the present application. The vehicle 1000 is provided with a battery 100 inside, and the battery 100 can be provided at the bottom, head or tail of the vehicle 1000. The battery 100 can be used to power the vehicle 1000, for example, the battery 100 can be used as an operating power source of the vehicle 1000.

[0038] The vehicle 1000 may further include a controller 200 and a motor 300 , wherein the controller 200 is used to control the battery 100 to supply power to the motor 300 , for example, to meet the power requirements of starting, navigating, and driving the vehicle 1000 .

[0039] In some embodiments of the present application, the battery 100 can not only serve as an operating power source for the vehicle 1000, but also serve as a driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0040] Figure 2 This is a schematic diagram of the exploded structure of the battery 100 provided in some embodiments of the present application. Figure 2 The battery 100 includes a housing 10 and a battery cell 20 , and the battery cell 20 is accommodated in the housing 10 .

[0041] The box body 10 is used to provide a storage space 11 for the battery cell 20. In some embodiments, the box body 10 may include a first portion 12 and a second portion 13, and the first portion 12 and the second portion 13 cover each other to define the storage space 11 for accommodating the battery cell 20. Of course, the connection between the first portion 12 and the second portion 13 can be sealed by a sealing member (not shown in the figure), and the sealing member can be a sealing ring, a sealant, etc.

[0042] The first part 12 and the second part 13 can be in various shapes, such as a cuboid, a cylinder, etc. The first part 12 can be a hollow structure with one side open to form a receiving cavity for receiving the battery cell 20, and the second part 13 can also be a hollow structure with one side open to form a receiving cavity for receiving the battery cell 20. The opening side of the second part 13 covers the opening side of the first part 12, thereby forming a box body 10 with a receiving space 11. Of course, if Figure 2 As shown, the first part 12 may be a hollow structure with one side open, and the second part 13 may be a plate-like structure. The second part 13 covers the open side of the first part 12 to form a box body 10 with an accommodating space 11.

[0043] In the battery 100, there can be one or more battery cells 20. If there are more than one battery cell 20, the battery cells 20 can be connected in series, in parallel or in a mixed connection. A mixed connection means that the battery cells 20 are connected in series and in parallel. The battery cells 20 can be directly connected in series, in parallel or in a mixed connection, and then the whole formed by the battery cells 20 can be accommodated in the box 10; of course, the battery cells 20 can be connected in series, in parallel or in a mixed connection to form a battery module, and then the battery modules can be connected in series, in parallel or in a mixed connection to form a whole, and then accommodated in the box 10. The battery cell 20 can be cylindrical, flat, rectangular or in other shapes. Figure 2 The example shows that the battery cell 20 is in a square shape.

[0044] In some embodiments, the battery 100 may further include a busbar component (not shown), and the multiple battery cells 20 may be electrically connected via the busbar component to achieve series connection, parallel connection, or mixed connection of the multiple battery cells 20 .

[0045] Figure 3 This is a schematic diagram of the structure of a battery cell 20 provided in some embodiments of the present application. Figure 4 This is a schematic diagram of the exploded structure of a battery cell 20 provided in some embodiments of the present application. Figure 3 and Figure 4 The battery cell 20 may include a housing 21 , an end cap assembly 22 and an electrode assembly 23 . The housing 21 has an opening 211 , the electrode assembly 23 is accommodated in the housing 21 , and the end cap assembly 22 is used to cover the opening 211 .

[0046] The shape of the housing 21 can be determined according to the specific shape of the electrode assembly 23. For example, if the electrode assembly 23 is a rectangular parallelepiped structure, the housing 21 can be a rectangular parallelepiped structure. Figure 3 and Figure 4 The case where the housing 21 and the electrode assembly 23 are square is exemplarily shown.

[0047] The shell 21 may also be made of a variety of materials, such as copper, iron, aluminum, stainless steel, aluminum alloy, etc., and the embodiment of the present application does not impose any special restrictions on this.

[0048] The end cap assembly 22 includes an end cap 221 and an electrode terminal 222. The end cap assembly 22 is used to seal the opening 211 of the housing 21 to form a closed installation space (not shown), and the installation space is used to accommodate the electrode assembly 23. The installation space is also used to accommodate an electrolyte, such as an electrolyte. The end cap assembly 22 is a component for outputting the electrical energy of the electrode assembly 23. The electrode terminal 222 in the end cap assembly 22 is used to be electrically connected to the electrode assembly 23, that is, the electrode terminal 222 is electrically connected to the tab of the electrode assembly 23. For example, the electrode terminal 222 is connected to the tab through the current collecting member 24 to achieve electrical connection between the electrode terminal 222 and the tab.

[0049] It should be noted that the opening 211 of the shell 21 can be one or two. If the opening 211 of the shell 21 is one, the end cap assembly 22 can also be one, and two electrode terminals 222 can be provided in the end cap assembly 22, and the two electrode terminals 222 are respectively used to electrically connect to the positive pole ear and the negative pole ear of the electrode assembly 23. If the opening 211 of the shell 21 is two, for example, the two openings 211 are provided on opposite sides of the shell 21, and the end cap assembly 22 can also be two, and the two end cap assemblies 22 are respectively covered at the two openings 211 of the shell 21. In this case, the electrode terminal 222 in one end cap assembly 22 can be a positive electrode terminal, which is used to electrically connect to the positive pole ear of the electrode assembly 23; the electrode terminal 222 in the other end cap assembly 22 can be a negative electrode terminal, which is used to electrically connect to the negative pole piece of the electrode assembly 23.

[0050] In some embodiments, Figure 4 As shown, the battery cell 20 may further include an insulating protective member 25 fixed to the periphery of the electrode assembly 23, and the insulating protective member 25 is used to insulate and isolate the electrode assembly 23 from the housing 21. Exemplarily, the insulating protective member 25 is a tape bonded to the periphery of the electrode assembly 23. In some embodiments, there are multiple electrode assemblies 23, and the insulating protective member 25 is arranged around the periphery of the multiple electrode assemblies 23, and the multiple electrode assemblies 23 are formed into an integral structure to keep the electrode assembly 23 structurally stable.

[0051] According to some embodiments of the present application, the present application provides an electrolyte, including a solvent and an electrolyte additive, wherein the solvent includes an oxidation-resistant solvent, and the oxidation voltage of the oxidation-resistant solvent is greater than 5V; and the electrolyte additive includes polyvinyl carbonate.

[0052] In some embodiments, polyvinylene carbonate is distributed in the electrolyte and is poorly soluble in the electrolyte, wherein "poorly soluble" means that at 25° C., the mass of the solid substance dissolved in 100 g of solvent when saturated is less than 0.01 g.

[0053] The oxidation voltage was tested by three electrodes. The test method was as follows: Pt electrode was used as the working electrode, and metal lithium was used as the counter electrode and reference electrode to test the oxidation voltage. The test instrument was an electrochemical workstation, with linear scanning voltammetry, a voltage range of OCV to 6V, a scanning speed of 0.1mV / s, and the oxidation voltage was > 5V vs.Li. + / Li solvents are available.

[0054] In the technical solution of the embodiment of the present application, by adding an oxidation-resistant solvent to the electrolyte, the oxidation resistance of the electrolyte can be improved and the interface between the positive electrode and the electrolyte can be stabilized; at the same time, polyvinyl carbonate is also added to the electrolyte, which can be adsorbed on the surface of the negative electrode to coat a layer of organic film before the oxidation-resistant solvent reacts with the negative electrode, so as to improve the compatibility between the oxidation-resistant solvent and the negative electrode, thereby improving the first coulombic efficiency and cycle performance of the battery.

[0055] According to some embodiments of the present application, the oxidation-resistant solvent includes one or more of sulfone organic solvents and nitrile organic solvents; optionally, the oxidation-resistant solvent includes one or more of ethyl methyl sulfone, methoxyethyl methyl sulfone, tetramethyl sulfone, adiponitrile, glutaronitrile and sebacate.

[0056] According to some embodiments of the present application, the mass ratio of polyvinylene carbonate to the oxidation-resistant solvent is 0.1%: 1 to 10%: 1, and can be optionally 0.5%: 1 to 3%: 1. Exemplarily, the mass ratio of polyvinylene carbonate to the oxidation-resistant solvent is 0.1%: 1, 0.5%: 1, 1.5%: 1, 3%: 1, 5%: 1, 7%: 1, 10%: 1, or an intermediate value between any two of the above values.

[0057] According to some embodiments of the present application, the mass proportion of the oxidation-resistant solvent in the electrolyte is 10% to 30%; the mass proportion of the polyvinylene carbonate in the electrolyte is 0.05% to 3%.

[0058] In the present application, the polyvinyl carbonate initially added to the electrolyte will be partially adsorbed on the negative electrode surface after the battery is assembled, and the remaining part will still be distributed in the electrolyte. The mass proportion of polyvinyl carbonate here refers to the polyvinyl carbonate distributed in the electrolyte.

[0059] According to some embodiments of the present application, the electrolyte additive further includes a coupling agent; optionally, the coupling agent includes one or more of a silane coupling agent and a titanate coupling agent.

[0060] In the present application, after the battery is assembled, at least a portion of the coupling agent initially added to the electrolyte will be adsorbed onto the surface of the negative electrode to connect with the polyvinylene carbonate.

[0061] According to some embodiments of the present application, the mass ratio of polyvinylene carbonate to coupling agent in the electrolyte is 1%:1 to 10%:1. Exemplarily, the mass ratio of polyvinylene carbonate to coupling agent in the electrolyte is 1%:1, 3%:1, 5%:1, 7%:1, 10%:1, or an intermediate value between any two of the above values. The coupling agent here also refers to the coupling agent present in the electrolyte.

[0062] According to some embodiments of the present application, the electrolyte also includes an organic solvent, and the organic solvent includes one or more of a carbonate solvent, a carboxylate solvent and an ether solvent; optionally, the carbonate solvent may be selected from one or more of ethylene carbonate (EC), ethylene carbonate, propylene carbonate, ethyl methyl carbonate (EMC), dimethyl carbonate, diethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, propylene carbonate (cyclic and chain) and fluoroethylene carbonate; the carboxylate solvent may be selected from one or more of methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate and 1,4-butyrolactone; the ether solvent may be selected from one or two of tetrahydrofuran and 1,3-dioxolane; optionally, the organic solvent includes one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate, etc., and propylene carbonate.

[0063] According to some embodiments of the present application, the mass ratio of the oxidation-resistant solvent to the organic solvent is 1:9 to 9:9, and can be optionally 1:9 to 3:9.

[0064] According to some embodiments of the present application, polyvinylene carbonate is distributed in the electrolyte in the form of particles, the number average molecular weight of polyvinylene carbonate is 10,000 to 200,000, and the test method is GPC (gel permeation chromatography); the true density of polyvinylene carbonate particles is 0.9 to 1.1 g / cm 3 , Test method: immersion method (specific gravity bottle method), Instrument: powder true density tester.

[0065] According to some embodiments of the present application, the electrolyte also includes a lithium salt, and the lithium salt can be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium dioxalatoborate, lithium difluorodioxalatophosphate and lithium tetrafluorooxalatophosphate.

[0066] According to some embodiments of the present application, the present application also provides a battery, comprising the electrolyte of any of the above schemes.

[0067] The battery in the present application includes any form of a single cell, a battery module and a battery pack. The battery includes a secondary battery, which can be a metal ion battery, wherein the metal ion battery is a battery system that releases capacity through a redox reaction between metal ions and metal elements. In some embodiments, the metal ion battery is a lithium ion battery, and in some other embodiments, the metal ion battery is a sodium ion battery or a battery of other metal ions.

[0068] According to some embodiments of the present application, a negative electrode plate is also included, and polyvinyl carbonate is adsorbed on the surface of the negative electrode plate.

[0069] According to some embodiments of the present application, a negative electrode plate is also included, and a coupling agent is adsorbed on the surface of the negative electrode plate.

[0070] In order to enable a clearer understanding of the technical solution of the present application, the embodiments of the present application are mainly described using lithium-ion batteries. Other types of batteries can be appropriately adjusted according to the battery type and will not be described in detail.

[0071] The lithium-ion battery provided in the present application includes an electrode assembly and an electrolyte of any of the above solutions, and the electrode assembly includes a positive electrode sheet, a negative electrode sheet and a separator.

[0072] [Positive electrode]

[0073] According to some embodiments of the present application, the positive electrode plate may include a positive electrode current collector and a positive electrode active material layer located on the surface of the positive electrode current collector, and the positive electrode active material layer provides lithium ions.

[0074] In some embodiments, the positive electrode current collector may be a material of various positive electrode current collectors suitable for lithium ion secondary batteries in the art, and a metal foil or a composite current collector may be used. Optionally, the positive electrode current collector may include but is not limited to metal foil, for example, aluminum foil may be used. The composite current collector may include a polymer material base and a metal layer formed on at least one surface of the polymer material base. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (for example, polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE) and other material substrates).

[0075] In some embodiments, the positive electrode active material layer may include a positive electrode active material, a conductive agent, a binder and any other components, and the positive electrode active material provides lithium ions. The positive electrode active material can be selected from any known positive electrode active material of a lithium ion battery. The positive electrode active material may include but is not limited to lithium transition metal composite oxides, etc., and the lithium transition metal composite oxide may include but is not limited to lithium cobalt oxide, lithium nickel oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphide, lithium manganese oxide, lithium iron manganese phosphide or these lithium transition metal oxides. Add other transition metals or non-transition metals to obtain compounds obtained by adding one or more of the above. The positive electrode includes one or more of ternary materials, lithium manganese-rich materials, lithium nickel manganese oxide materials, lithium cobalt phosphate materials, etc.

[0076] [Negative electrode]

[0077] According to some embodiments of the present application, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, and the negative electrode active material layer may include a negative electrode active material. As an example, the negative electrode current collector has two surfaces opposite to each other in its own thickness direction, and the negative electrode active material layer is disposed on any one or both of the two opposite surfaces of the negative electrode current collector.

[0078] In some embodiments, the negative electrode current collector may be any material suitable for use as a negative electrode current collector for a lithium-ion secondary battery in the art, and the negative electrode current collector may be a metal foil or a composite current collector. Alternatively, the negative electrode current collector may include but is not limited to a metal foil, for example, a copper foil may be used. The composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of a polymer material substrate. The composite current collector may be formed by forming a metal material (copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer material substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0079] In some embodiments, the negative electrode active material can be various negative electrode active materials suitable for lithium ion secondary batteries in the art. As an example, the negative electrode active material can include but is not limited to carbon materials (graphite, soft carbon, hard carbon, mesophase carbon microspheres, carbon fiber, carbon nanotubes, graphene, etc.), titanium oxide-based materials (lithium titanate, titanium dioxide, etc.), alloyed negative electrode materials (silicon-based materials, tin-based materials, germanium-based materials, etc.), conversion-type negative electrode materials (transition metal oxides, phosphides, sulfides, nitrides, etc.). These negative electrode active materials can be used alone or in combination of two or more. Graphite can be selected from one or more combinations of artificial graphite, natural graphite and modified graphite, and graphite can be further modified. The modification method of graphite is not specifically limited, such as coating modification on the graphite surface.

[0080] In some embodiments, the negative electrode active material layer may further include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA) and carboxymethyl chitosan (CMCS).

[0081] In some embodiments, the negative electrode active material layer may further include a conductive agent, which may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0082] In some embodiments, the negative electrode active material layer may further include other additives, such as a thickener (eg, sodium carboxymethyl cellulose (CMC-Na)).

[0083] In some embodiments, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on the negative electrode collector, and after drying, cold pressing and other processes, the negative electrode sheet can be obtained.

[0084] [Isolation film]

[0085] The present application has no particular limitation on the type of isolation membrane, and any known porous isolation membrane with good chemical stability and mechanical stability can be selected.

[0086] In some embodiments, the isolation membrane may be a multilayer composite membrane formed by one or more combinations of materials including but not limited to polyethylene, polypropylene, non-woven fabrics, and polyfiber materials. The isolation membrane may be a single-layer film or a multilayer composite film, without particular limitation. When the isolation membrane is a multilayer composite film, the materials of each layer may be the same or different, without particular limitation.

[0087] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0088] In some embodiments, the battery may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0089] In some embodiments, the outer packaging of the battery may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery may also be a soft package, such as a bag-type soft package. The material of the soft package may be plastic, and examples of the plastic include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0090] According to some embodiments of the present application, the present application also provides an electrical device, comprising a battery according to any of the above schemes.

[0091] Next, one or more embodiments are described in more detail with reference to the following examples. Of course, these examples do not limit the scope of one or more embodiments.

[0092] Examples and Comparative Examples

[0093] Example 1

[0094] (1) Preparation of electrolyte:

[0095] The solvent, lithium salt and electrolyte additive are mixed and stirred evenly to obtain an electrolyte. The solvent is an organic solvent + an oxidation-resistant solvent, the mass ratio of the oxidation-resistant solvent to the organic solvent is 2:9, the organic solvent is ethylene carbonate + ethyl methyl carbonate, the volume ratio of ethylene carbonate to ethyl methyl carbonate is 3:7, the oxidation-resistant solvent is adiponitrile, the lithium salt is lithium hexafluorophosphate, and the electrolyte additive is polyvinylene carbonate (number average molecular weight is 100,000, true density is 1g / cm 3 ); the lithium salt concentration in the electrolyte is 1 mol / L, and the mass ratio of the electrolyte additive to the oxidation-resistant solvent is 1%:1.

[0096] (2) Preparation of positive electrode sheet and anode electrode sheet:

[0097] Preparation of positive electrode sheet: The positive electrode active material NCM523 material, conductive carbon black, and binder polyvinylidene fluoride (PVDF) are fully stirred and mixed in an N-methylpyrrolidone solvent system at a weight ratio of 96:2:2 to obtain a positive electrode slurry; the positive electrode slurry is evenly coated on a positive electrode current collector aluminum foil with a thickness of 13 μm at a coating speed of 30 m / min; the temperature of the coating oven is 120°C, and then the positive electrode sheet is obtained by cold pressing and slitting;

[0098] Preparation of negative electrode sheets: The negative electrode active material graphite and conductive carbon black, binder styrene-butadiene rubber (SBR), and thickener sodium carboxymethyl cellulose (CMC-Na) are fully stirred and mixed in a deionized water solvent system at a mass ratio of 95:2:2:1 to obtain a negative electrode slurry; the negative electrode slurry is evenly coated on a negative electrode current collector copper foil with a thickness of 6 μm, the coating speed is 25 m / min, and the temperature of the coating oven is 120°C; then the negative electrode sheets are obtained by cold pressing and slitting.

[0099] (3) Preparation of battery: Then, the bare cell is assembled in the order of positive electrode sheet, separator, and negative electrode sheet, and the above-mentioned electrolyte is injected to obtain a lithium-ion battery.

[0100] Examples 2 to 10 and Comparative Examples 1 to 4

[0101] The electrolytes and batteries of the examples and comparative examples were prepared by a method similar to that of Example 1. The differences between the examples and comparative examples are shown in Table 1.

[0102] Test Section

[0103] (1) First Coulomb efficiency test

[0104] The secondary batteries prepared above were subjected to the following tests:

[0105] Formation: The unformed secondary battery is first charged to 3.4V at 25℃ and 0.1C, and then charged to 3.8V at 0.33C. The charge capacity is counted as C0.

[0106] Capacity test: first discharge to 2.5V, the discharge capacity is counted as D0; then charge to 4.6V at 0.33C constant current, then charge to 0.05C at 4.6V constant voltage, the charge capacity is counted as C1; after 10 minutes of storage, discharge to 2.5V at 0.33C constant current, the discharge capacity is counted as D1. Calculate the first coulomb efficiency of the secondary battery according to the following formula:

[0107] First coulombic efficiency (%) = D1 / (C0+C1-D0).

[0108] (2) 25℃ cycle test

[0109] At 25°C, the secondary battery after the capacity test is charged to 4.9V at a constant current of 0.33C, then charged at a constant voltage of 4.9V until the current is less than 0.05C, and then the secondary battery is discharged to 2.5V at a constant current of 0.33C to obtain the discharge capacity at 0.05C, which is counted as one cycle. Repeat the above charging and discharging steps until the capacity retention rate reaches 70% SOH, at which point the number of cycles represents the battery cycle performance.

[0110] The capacity retention rate calculation formula is: Capacity retention rate = discharge capacity in the last week / discharge capacity in the first week.

[0111] The performance and composition of the detected battery are shown in Table 1:

[0112] Table 1 Composition and performance of batteries

[0113]

[0114]

[0115] Combining the results in Table 1, we can see that:

[0116] Compared with Comparative Examples 1 to 4, Examples 1 to 8 simultaneously add an oxidation-resistant solvent and polyvinylene carbonate to the electrolyte, which can improve the initial coulombic efficiency and cycle performance of the battery.

[0117] Compared with Comparative Example 1, Example 1 directly adds the film-forming product polyvinyl carbonate into the electrolyte, which can effectively improve the initial coulombic efficiency and cycle performance of the battery.

[0118] According to Examples 1 to 5, it is found that the mass ratio of polyvinyl carbonate added to the oxidation-resistant solvent in the electrolyte is 0.1%:1 to 10%:1, and can be optionally 0.5%:1 to 1.5%:1, which can improve the initial coulombic efficiency and cycle performance of the battery.

[0119] According to Example 3 and Example 6, the mass ratio of the oxidation-resistant solvent to the organic solvent is 1:9 to 2:9, which can improve the initial coulombic efficiency and cycle performance of the battery.

[0120] According to Example 1 and Example 7, the sulfone solvent or nitrile solvent added to the electrolyte as an oxidation-resistant solvent can improve the initial coulombic efficiency and cycle performance of the battery.

[0121] According to Example 8, polyvinyl carbonate and a coupling agent added simultaneously to the electrolyte can significantly improve the initial coulombic efficiency and cycle performance of the battery.

[0122] The embodiments described above are part of the embodiments of the present application, rather than all of the embodiments. The detailed description of the embodiments of the present application is not intended to limit the scope of the present application for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present application.

Claims

1. An electrolyte, characterized in that: The invention comprises a solvent and an electrolyte additive, wherein the solvent comprises an oxidation-resistant solvent, and the oxidation voltage of the oxidation-resistant solvent is greater than 5V; and the electrolyte additive comprises polyvinylene carbonate.

2. The electrolyte according to claim 1, characterized in that The oxidation-resistant solvent includes one or more of sulfone solvents and nitrile solvents; optionally, the oxidation-resistant solvent includes one or more of ethyl methyl sulfone, methoxyethyl methyl sulfone, tetramethyl sulfone, adiponitrile, glutaronitrile and sebaconitrile.

3. The electrolyte according to claim 1 or 2, characterized in that The mass ratio of the polyvinylene carbonate to the oxidation-resistant solvent is 0.1%:1 to 10%:1, and can be optionally 0.5%:1 to 3%:

1.

4. The electrolyte according to any one of claims 1 to 3, characterized in that The mass proportion of the oxidation-resistant solvent in the electrolyte is 10% to 30%; the mass proportion of the polyvinylene carbonate in the electrolyte is 0.05% to 3%.

5. The electrolyte according to any one of claims 1 to 4, characterized in that The electrolyte additive further includes a coupling agent; optionally, the coupling agent includes one or more of a silane coupling agent and a titanate coupling agent.

6. The electrolyte according to claim 5, characterized in that The mass ratio of the polyvinylene carbonate to the coupling agent in the electrolyte is 1%:1 to 10%:

1.

7. The electrolyte according to any one of claims 1 to 6, characterized in that The solvent also includes an organic solvent, which includes one or more of a carbonate solvent, a carboxylate solvent and an ether solvent; optionally, the organic solvent also includes one or more of ethylene carbonate, ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate and propylene carbonate.

8. The electrolyte according to claim 7, characterized in that The mass ratio of the oxidation-resistant solvent to the organic solvent is 1:9 to 9:9, and can be optionally 1:9 to 3:

9.

9. The electrolyte according to any one of claims 1 to 8, characterized in that The polyvinylene carbonate is distributed in the electrolyte in the form of particles; the molecular weight of the polyvinylene carbonate is 10,000 to 200,000, and the true density of the polyvinylene carbonate particles is 0.9 to 1.1 g / cm 3 .

10. A battery, characterized in that: The electrolyte comprising the electrolyte according to any one of claims 1 to 9.

11. The battery according to claim 10, characterized in that It also includes a negative electrode plate, on the surface of which polyvinyl carbonate is adsorbed.

12. The battery according to claim 10 or 11, characterized in that: It also includes a negative electrode plate, and a coupling agent is adsorbed on the surface of the negative electrode plate.

13. An electrical device, characterized in that: A battery comprising the battery according to any one of claims 10 to 12.

Images