Electrode plates, lithium-ion batteries, battery units, battery packs, and electrical devices

Abstract

The present application provides a plate, a lithium ion battery, a battery unit, a battery pack and an electric device. The electrode plate according to the present application includes a current collector and an active material layer provided on at least one surface of the current collector, the active material layer including a lithium salt surfactant. The application utilizes the affinity between the lithium salt surfactant and an electrolyte to effectively reduce the surface tension of the electrolyte, improve the wettability of the electrolyte to the electrode plate, reduce the interface resistance of the battery, and improve the utilization efficiency of the active material, thereby realizing improvements in the rate performance, discharge capacity, and service life of the lithium ion battery.

Description

[Technical Field]

[0001] This application relates to the technical field of lithium batteries, and more particularly to electrodes, lithium-ion batteries, battery units, battery packs, and electrical devices.

[0002] (Cross-reference of related applications) This application claims priority based on the Chinese patent application filed on November 12, 2021, titled "Electrode Plates, Lithium-ion Batteries, Battery Units, Battery Packs and Electrical Devices," with application number 202111337252.X, the entirety of which is incorporated by reference to this application. [Background technology]

[0003] Lithium-ion batteries are rechargeable batteries that generally consist of a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions repeatedly insert and remove between the positive and negative electrode plates. The electrolyte is the carrier for ion transport in lithium-ion batteries, transporting ions between the positive and negative electrodes and ensuring that the lithium-ion battery can achieve performance such as high voltage and high specific energy. The electrolyte is generally obtained by mixing raw materials such as high-purity organic solvents, lithium electrolyte salts, and necessary additives in specified proportions under specified conditions.

[0004] Currently, lithium-ion batteries are widely used in high-tech products such as automobiles and mobile phones. As the application areas of lithium-ion batteries expand, there is a need to improve the various performance aspects of these batteries. [Overview of the project] [Problems that the invention aims to solve]

[0005] This application has been made in view of the above-mentioned problems, and aims to provide an electrode plate that can improve the rate performance, discharge capacity, and service life of a lithium-ion battery, a lithium-ion battery including the electrode plate, a battery unit, a battery pack, and an electrical device. [Means for solving the problem]

[0006] To achieve the above objective, the first aspect of this application provides an electrode plate. The electrode plate comprises a current collector and an active material layer provided on at least one surface of the current collector, wherein the active material layer contains a lithium salt surfactant. This application demonstrates how doping the active material layer of the electrode plate with a lithium salt surfactant can effectively reduce the surface tension of the electrolyte by utilizing the affinity between the lithium salt and the electrolyte, thereby improving the wettability of the electrolyte to the electrode plate, reducing the interfacial resistance of the battery, and improving the utilization efficiency of the active material. This can lead to improvements in the rate performance, discharge capacity, and service life of lithium-ion batteries.

[0007] In any embodiment, a functional layer is provided on the surface of the active material layer that is spaced apart from the current collector, and the functional layer also contains the lithium surfactant salt. In any embodiment, the amount of substance of the lithium salt surfactant in the active material layer is 0.00175 to 0.00875 mol. In any embodiment, the lithium surfactant salt is at least one selected from lithium bis(trifluoromethanesulfonyl)imide, lithium nitrate, lithium perchlorate, or lithium chloride.

[0008] In any embodiment, the active material layer includes several active material sublayers stacked in an order of increasing coating mass per unit area along a direction away from the current collector, and the amount of lithium surfactant salt contained in the several active material sublayers also changes in increasing order. In these embodiments, the active material layer on the electrode plate is multilayer coated, each active material sublayer is doped with lithium surfactant salt, and the amount of lithium surfactant salt used in each active material sublayer varies according to the coating mass of the active material in the active material sublayer, thereby playing a role in pore formation in each active material sublayer.

[0009] In any embodiment, the active material layer includes a first active material sublayer and a second active material sublayer that are sequentially laminated along a direction away from the current collector, and the coating mass per unit area of ​​the first active material sublayer is CW1, where CW1 is 0.150 g / 1540.25 mm 2 ≤CW1 ≤ 0.200g / 1540.25mm 2 The following conditions are met, and the coating mass per unit area of ​​the second active material sublayer is CW2, where CW2 ≥ 0.200 g / 1540.25 mm 2 When the following conditions are met, and the amount of lithium surfactant salt in the first active material sublayer is M1, the amount of lithium surfactant salt in the second active material sublayer is M2, and the amount of lithium surfactant salt in the functional layer is M3, then M1 / (M1+M2+M3) is 10% to 30%, and arbitrarily 20%, M2 / (M1+M2+M3) is 20% to 40%, and arbitrarily 30%, and M3 / (M1+M2+M3) is 30% to 70%, and arbitrarily 50%. In any embodiment, the electrode plate is either a positive electrode plate or a negative electrode plate.

[0010] The second aspect of this application provides a lithium-ion battery. The lithium-ion battery includes a positive electrode plate, a negative electrode plate, a separator placed between the positive electrode plate and the negative electrode plate, and an electrolyte, wherein at least one of the positive electrode plate and the negative electrode plate is an electrode plate according to the first aspect of this application.

[0011] In any embodiment, the electrolyte is selected from an ester-based electrolyte, an ether-based electrolyte, or an aqueous electrolyte.

[0012] In any embodiment, the electrolyte is a pure solvent electrolyte. That is, the electrolyte contains only a solvent and does not contain an electrolyte lithium salt. When the electrolyte does not contain an electrolyte lithium salt, all lithium salts are doped as surfactants into the active material layer on the surface of the electrode or the functional coating layer on the surface of the active material layer, and the direct electrolyte solvent is injected into the battery as the electrolyte. After the electrolyte solvent infiltrates the electrode plate, the surfactant lithium salt on the electrode plate dissolves in the electrolyte, whereby ions can be transported. If a pure solvent is injected into the battery as the electrolyte, since the viscosity of the pure solvent is relatively low, the wettability with respect to the electrode plate is better. And after the surfactant lithium salt doped on the electrode plate dissolves, further pore formation on the electrode is realized, a porous electrode is manufactured, and the wettability of the electrolyte with respect to the electrode plate can be promoted better.

[0013] In any embodiment, the solvent in the electrolyte is at least one selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate or ethyl methyl carbonate.

[0014] In any embodiment, in the active material layer and the functional layer of the electrode plate, when the total amount of substance of the surfactant lithium salt is Mp, the amount of substance of the lithium salt in the electrolyte is Ms, and the total volume of the electrolyte is Vs, in the lithium ion battery, (Mp + Ms) / Vs is 1 to 2 mol / L. Optionally, (Mp + Ms) / Vs is 1 mol / L. If the doping concentration of the surfactant lithium salt on the electrode plate is kept within an appropriate range, it contributes to the wettability of the electrolyte with respect to the electrode plate, and without impairing the ionic conductivity, there is no increase in the polarization of the battery, and the electrochemical performance of the entire lithium ion battery can be guaranteed.

[0015] The third aspect of this application further provides a battery unit. The battery unit includes the lithium ion battery according to the second aspect of this application.

[0016] A fourth aspect of this application further provides a battery pack, which includes a lithium-ion battery according to the second aspect of this application or a battery unit according to the third aspect of this application.

[0017] A fifth aspect of this application further provides an electrical device, which includes a lithium-ion battery according to the second aspect of this application, a battery unit according to the third aspect of this application, or a battery pack according to the fourth aspect of this application. The lithium-ion battery, battery unit, or battery pack is used as a power source or energy storage unit for the electrical device.

[0018] The lithium-ion battery according to the second phase, the battery unit according to the third phase, the battery pack according to the fourth phase, and the electrical device according to the fifth phase of this application include the electrode plates according to the first phase of this application, and therefore have relatively good rate performance, discharge capacity, and a relatively long service life. [Brief explanation of the drawing]

[0019] [Figure 1] This is a scanning electron microscope image of the contact angle between a negative electrode plate (which does not contain the lithium salt surfactant in its active material layer) and the electrolyte. [Figure 2] This is a scanning electron microscope image of the contact angle between a negative electrode plate containing a low concentration of lithium salt surfactant in its active material layer and the electrolyte. [Figure 3] This is a scanning electron microscope image of the contact angle between a negative electrode plate containing a high concentration of the surfactant lithium salt in its active material layer and the electrolyte. [Figure 4] This is a schematic diagram of a lithium-ion battery according to one embodiment of the present application. [Figure 5] Figure 4 is an exploded view of a lithium-ion battery according to one embodiment of the present application. [Figure 6] This is a schematic diagram of a battery unit according to one embodiment of the present application. [Figure 7] This is a schematic diagram of a battery pack according to one embodiment of the present application. [Figure 8] Figure 7 is an exploded view of a battery pack according to one embodiment of this application. [Figure 9] This is a schematic diagram of an electrical device that uses a lithium-ion battery as a power source according to one embodiment of the present application. [Modes for carrying out the invention]

[0020] Hereinafter, embodiments of the lithium-ion battery, battery unit, battery pack, and electrical device relating to this application will be described and specifically disclosed with reference to the drawings. However, detailed explanations of non-essential matters may be omitted. For example, detailed explanations of well-known matters and redundant explanations of similar configurations may be omitted. This is to avoid making the following explanation unnecessarily long and to ensure that it is easily understood by those skilled in the art. Furthermore, the drawings and the following explanation are intended to enable those skilled in the art to fully understand this application and do not limit the subject matter described in the claims.

[0021] The “range” disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit. The selected lower limit and upper limit define the limits of a particular range. The range thus defined may or may not include the limit and can be in any combination; that is, it is possible to define a range with any combination of a lower limit and an upper limit. For example, if the ranges 60-120 and 80-110 are given for a particular parameter, it should be understood that the ranges 60-110 and 80-120 are also predictable. Also, if the lower limits are 1 and 2 and the upper limits are 3, 4 and 5, then any of the ranges 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5 are also predictable. In this application, unless otherwise stated, “a-b” in numerical ranges is an abbreviation for any combination of real numbers between real number a and real number b. For example, the numerical range "0 to 5" includes all real numbers between "0 to 5" as specified in the specification, and "0 to 5" is merely an abbreviated representation of combinations of these numbers. Also, if a parameter is expressed as an integer of 2 or more, it is equivalent to disclosing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0022] Unless otherwise stated, all embodiments and optional embodiments of this application can be combined to form new technical inventions.

[0023] Unless otherwise stated, all technical features of this application and the selectable technical features can be combined to form a new technical invention.

[0024] Unless otherwise stated, all steps of this application may be performed sequentially or randomly. It is preferable that they be performed sequentially. For example, if the method includes step (a) and step (b), the method may include step (a) and step (b) performed in order, or step (b) and step (a) performed in order. For example, the method may further include step (c), and step (c) may be incorporated into the method in any order, for example, step (a), step (b) and step (c), step (a), step (c) and step (b), or step (c), step (a) and step (b), and so on.

[0025] Unless otherwise specified, the terms “includes” and “inclusion” in this application may be open or closed. For example, when “includes” and “inclusion” are used, they may include or include elements not listed, or they may include or include only the listed elements.

[0026] Unless otherwise stated, the term "or" in this application is a broad expression. For example, the phrase "A or B" means "A, B, or A and B." More specifically, the conditions "A or B" are met when A is true (or exists) and B is false (or does not exist), when A is false (or does not exist) and B is true (or exists), and when both A and B are true (or exist).

[0027] [Pole plate] In one embodiment of this application, the application provides an electrode plate. The electrode plate comprises a current collector and an active material layer provided on at least one surface of the current collector, wherein the active material layer contains a lithium salt surfactant.

[0028] This application is made based on the following idea. Inside a lithium-ion battery, when the wetting effect of the electrolyte is weak, the ion transport path becomes longer, the reciprocation of lithium ions between the positive and negative electrodes is hindered, the electrode plates not in contact with the electrolyte cannot participate in the electrochemical reaction of the battery, and the interfacial resistance of the battery increases, impairing the rate performance, discharge capacity, and service life of the lithium battery. Inside a lithium-ion battery, the interfacial wettability between the electrolyte and the electrode is represented by Young's equation.

[0029] γ SV =γ SL +γ LV ×cosθ

[0030] γ SV is the surface tension of the electrode plate, γ SL is the surface tension of the contact surface between the electrolyte and the electrode, γ LV is the surface tension of the electrolyte itself, and θ is the contact angle between the electrolyte and the electrode.

[0031] As can be seen from the above formula, when the electrode plate and the gas-phase interface are constant, the surface tension of the electrolyte determines the size of the contact angle. The smaller the surface tension of the electrolyte, the smaller the interfacial contact angle and the better the wettability of the electrolyte to the electrode plate. Based on this, the inventors designed as follows. The active material layer of the electrode plate is doped with a surfactant lithium salt. When the electrode plate comes into contact with the electrolyte, the surfactant lithium salt partially or completely dissolves in the electrolyte. By utilizing the affinity between the surfactant lithium salt and the electrolyte, the surface tension of the electrolyte is effectively reduced, and the wettability of the electrolyte to the electrode plate is improved, thereby realizing improvements in the rate performance, discharge capacity, and service life of the lithium-ion battery. A surfactant is a substance that significantly reduces the surface tension of the target solution. The surfactant lithium salt according to this application means a lithium salt that significantly reduces the surface tension of the electrolyte.

[0032] In some embodiments, a functional layer is provided on the surface of the active material layer spaced apart from the current collector, and the functional layer also contains the lithium surfactant salt. In these embodiments, the lithium surfactant salt is contained in both the active material layer and the functional layer. When the electrode plate comes into contact with the electrolyte, the lithium surfactant salt in the active material layer and functional layer of the electrode plate partially or completely dissolves in the electrolyte, and together they function to reduce the surface tension of the electrolyte and improve the wettability of the electrolyte to the electrode plate, thereby improving the rate performance, discharge capacity and service life of the lithium-ion battery.

[0033] In some embodiments, the lithium surfactant salt is at least one selected from lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), lithium nitrate (LiNO3), lithium perchlorate (LiClO4), and lithium chloride (LiCl).

[0034] In some embodiments, the amount of the lithium salt surfactant in the active material layer is 0.00175 to 0.00875 mol.

[0035] The inventors used lithium bis(trifluoromethanesulfonyl)imide salt as a lithium surfactant and prepared aqueous solutions at concentrations of 5% and 10%, respectively, which were then coated onto the surface of a negative electrode plate. The contact angles between the negative electrode plate coated with different concentrations and the electrolyte were then measured, and the measurement results are shown in Figures 1 to 3. Figure 1 is a scanning electron microscope image of the contact angle between the negative electrode plate and the electrolyte when no lithium surfactant salt is contained inside or on the surface of the electrode plate. Figure 2 is a scanning electron microscope image of the contact angle between the negative electrode plate and the electrolyte when a low concentration of lithium surfactant salt is contained inside or on the surface of the electrode plate. Figure 3 is a scanning electron microscope image of the contact angle between the negative electrode plate and the electrolyte when a high concentration of lithium surfactant salt is contained inside or on the surface of the electrode plate. As can be seen from the contact angle measurement results shown in Figures 1 to 3, the wetting effect between the electrolyte and the surface of the negative electrode plate can be effectively improved by applying lithium salt surfactants. It has been shown that the wetting effect is improved even with the application of low concentrations of lithium salt surfactants, and the higher the concentration of lithium salt surfactant used, the better the wetting effect.

[0036] In some embodiments, the active material layer includes several active material sublayers stacked in an order of increasing coating mass per unit area along a direction away from the current collector, and the amount of lithium surfactant salt contained in the several active material sublayers also changes in increasing order. In these embodiments, the active material layer on the electrode plate is multilayer coated, each active material sublayer is doped with lithium surfactant salt, and the amount of lithium surfactant salt used in each active material sublayer varies according to the coating mass of the active material in the active material sublayer, thereby playing a role in pore formation in each active material sublayer.

[0037] In some embodiments, the active material layer includes a first active material sublayer and a second active material sublayer that are sequentially laminated along a direction away from the current collector. The coating mass per unit area of ​​the first active material sublayer is denoted as CW1, where CW1 is 0.150 g / 1540.25 mm 2 ≤CW1 ≤ 0.200g / 1540.25mm 2The following conditions are met: The coating mass per unit area of ​​the second active material sublayer is CW2, and CW2 ≥ 0.200 g / 1540.25 mm 2 The following conditions are met. When the amount of lithium surfactant salt in the first active material sublayer is M1, the amount of lithium surfactant salt in the second active material sublayer is M2, and the amount of lithium surfactant salt in the functional layer is M3, then M1 / (M1+M2+M3) is 10% to 30%, and arbitrarily 20%, M2 / (M1+M2+M3) is 20% to 40%, and arbitrarily 30%, and M3 / (M1+M2+M3) is 30% to 70%, and arbitrarily 50%. In any embodiment, the electrode plate is either a positive electrode plate or a negative electrode plate.

[0038] [Lithium-ion battery] Another embodiment of this application provides a lithium-ion battery, the lithium-ion battery comprising a positive electrode plate, a negative electrode plate, a separator placed between the positive electrode plate and the negative electrode plate, and an electrolyte, wherein at least one of the positive electrode plate and the negative electrode plate is an electrode plate according to the first aspect of this application. In some embodiments, the electrolyte includes an ester-based electrolyte, an ether-based electrolyte, or an aqueous electrolyte.

[0039] In some embodiments, the electrolyte is a pure solvent electrolyte, that is, the electrolyte contains only the solvent and does not contain electrolyte lithium salts. When the electrolyte does not contain electrolyte lithium salts, all lithium salts are doped as surfactants into the active material layer on the electrode surface or into the functional coating layer on the surface of the active material layer, and the electrolyte solvent is directly injected into the battery as the electrolyte. After the electrolyte solvent has permeated the electrode plate, the surfactant lithium salts on the electrode plate dissolve in the electrolyte, thereby enabling ion transport. If a pure solvent is injected into the battery as the electrolyte, the viscosity of the pure solvent is relatively low, resulting in better wettability to the electrode plate. After the surfactant lithium salts doped into the electrode plate dissolve, pore formation in the electrode is further realized, a porous electrode is manufactured, and the wettability of the electrolyte to the electrode plate can be further improved. In some embodiments, the solvent in the electrolyte is at least one selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate, or ethylmethyl carbonate. In some embodiments, when the total amount of the lithium surfactant in the active material layer and functional layer of the electrode plate is Mp, the amount of lithium salt in the electrolyte is Ms, and the total volume of the electrolyte is Vs, then in the lithium-ion battery, (Mp + Ms) / Vs is 1 to 2 mol / L, and optionally, (Mp + Ms) / Vs is 1 mol / L. By keeping the doping concentration of the lithium surfactant in the electrode plate within an appropriate range, it is possible to contribute to the wettability of the electrolyte to the electrode plate, without impairing ionic conductivity, without increasing the polarization of the battery, and to guarantee the electrochemical performance of the entire lithium-ion battery.

[0040] The lithium-ion battery, battery unit, battery pack, and electrical device related to this application will be described below with reference to the drawings.

[0041] Generally, a lithium-ion battery includes a positive electrode plate, a negative electrode plate, an electrolyte, and a separator. During the charging and discharging process of the battery, active ions are repeatedly inserted into and removed from the positive and negative electrode plates. The electrolyte transports ions between the positive and negative electrode plates. The separator is placed between the positive and negative electrode plates and primarily prevents short circuits between the positive and negative electrodes while allowing ions to pass through.

[0042] [Positive plate] The positive electrode plate includes a positive electrode current collector and a positive electrode active material layer provided on at least one surface of the positive electrode current collector. In some embodiments, the positive electrode active material layer contains a lithium surfactant salt. In some embodiments, a functional layer is provided on a surface of the positive electrode active material layer spaced apart from the current collector, and the functional layer also contains a lithium surfactant salt. For example, the positive electrode current collector has two opposing surfaces in its thickness direction, and the positive electrode active material layer is provided on one or both of the two opposing surfaces of the positive electrode current collector.

[0043] In some embodiments, a metal foil or a composite current collector is used as the positive electrode current collector. For example, aluminum foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by providing a metal material (such as aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0044] The positive electrode active material layer further contains a positive electrode active material. In some embodiments, the positive electrode active material can be any positive electrode active material for batteries that is well known in the art. For example, the positive electrode active material may include at least one of an olivine-structured lithium-containing phosphate, a lithium transition metal oxide, and a modified compound thereof. This application is not limited to these materials, and other conventional materials usable as positive electrode active materials for batteries may be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include lithium cobalt oxide (e.g., LiCoO2), lithium nickel oxide (e.g., LiNiO2), lithium manganese oxide (e.g., LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, and lithium nickel cobalt manganese oxide (e.g., LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (simply NCM) 333 (Sometimes referred to as) LiNi 0.5 Co 0.2 Mn 0.3 O2 (simply NCM) 523 (Sometimes referred to as) LiNi 0.5 Co 0.25 Mn 0.25 O2 (simply NCM) 211 (Sometimes referred to as) LiNi0.6 Co 0.2 Mn 0.2 O2 (simply NCM) 622 (Sometimes referred to as) LiNi 0.8 Co 0.1 Mn 0.1 O2 (simply NCM) 811 (sometimes referred to as), lithium nickel cobalt aluminum oxide (e.g., LiNi 0.85 Co 0.15 Al 0.05 This includes, but is not limited to, at least one of the following: O2) and modified compounds. Examples of lithium-containing phosphates with an olivine structure include, but is not limited to, at least one of the following: lithium iron phosphate (e.g., LiFePO4 (sometimes simply referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (e.g., LiMnPO4), lithium manganese phosphate and carbon composites, lithium iron manganese phosphate, and lithium iron manganese phosphate and carbon composites.

[0045] In some embodiments, the positive electrode active material layer optionally further includes a binder. For example, the binder includes at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), a ternary copolymer of vinylidene fluoride-tetrafluoroethylene-propylene, a ternary copolymer of vinylidene fluoride-hexafluoropropene-tetrafluoroethylene, a copolymer of tetrafluoroethylene-hexafluoropropene, and a fluorine-containing acrylic resin.

[0046] In some embodiments, the positive electrode active material layer optionally further includes a conductive agent. For example, the conductive agent includes at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0047] In some embodiments, a positive electrode plate can be prepared by the following method. The above components for preparing a positive electrode plate, such as a positive electrode active material, a lithium surfactant (for example, the positive electrode active material layer contains a lithium surfactant), a conductive agent, a binder, and other optional components, are dispersed in a solvent (for example, N-methylpyrrolidone) to form a positive electrode slurry, the positive electrode slurry is applied to a positive electrode current collector, and dried. If a positive electrode functional layer is further provided on the surface of the positive electrode active material layer, and the positive electrode functional layer also contains a lithium surfactant, then an aqueous solution of a predetermined concentration using the lithium surfactant is prepared and applied to the surface of the positive electrode plate, and the positive electrode plate is obtained through processes such as drying and cold pressing.

[0048] [negative electrode plate] In some embodiments, the negative electrode plate includes a negative electrode current collector and a negative electrode active material layer provided on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer contains a lithium surfactant. In some embodiments, a functional layer is provided on the surface of the negative electrode active material layer spaced apart from the current collector, and the functional layer also contains a lithium surfactant. For example, the negative electrode current collector has two opposing surfaces in its thickness direction, and the negative electrode active material layer is provided on one or both of the two opposing surfaces of the negative electrode current collector.

[0049] In some embodiments, a metal foil or a composite current collector is used as the negative electrode current collector. For example, copper foil can be used as the metal foil. The composite current collector may include a polymer material substrate and a metal layer formed on at least one surface of the polymer material substrate. The composite current collector can be formed by providing a metal material (such as copper, copper alloys, nickel, nickel alloys, titanium, titanium alloys, silver, and silver alloys) on a polymer material substrate (for example, a substrate such as polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), or polyethylene (PE)).

[0050] The negative electrode active material layer further contains a negative electrode active material. In some embodiments, the negative electrode active material can be any negative electrode active material for batteries that is well known in the art. For example, the negative electrode active material may include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate. The silicon-based material is at least one selected from elemental silicon, silicon oxide, silicon-carbon composite, silicon-nitrogen composite, and silicon alloy. The tin-based material is at least one selected from elemental tin, tin oxide, and tin alloy. This application is not limited to these materials, and other conventional materials usable as negative electrode active materials for batteries may be used. These negative electrode active materials may be used individually or in combination of two or more.

[0051] In some embodiments, the negative electrode active material layer optionally further includes a binder. The binder is at least one selected from 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).

[0052] In some embodiments, the negative electrode active material layer optionally further contains a conductive agent. The conductive agent is at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. In some embodiments, the negative electrode active material layer optionally further contains other additives, such as thickeners (e.g., sodium carboxymethylcellulose (CMC-Na)).

[0053] In some embodiments, a negative electrode plate can be prepared by the following method. The above components for preparing the negative electrode plate, such as a negative electrode active material, a lithium surfactant (for example, the negative electrode active material layer contains a lithium surfactant), a conductive agent, a binder, and other optional components are dispersed in a solvent (for example, deionized water) to form a negative electrode slurry, the negative electrode slurry is applied to a negative electrode current collector, and dried. If a negative electrode functional layer is further provided on the surface of the negative electrode active material layer, and the negative electrode functional layer also contains a lithium surfactant, then an aqueous solution of a predetermined concentration is prepared using the lithium surfactant and applied to the surface of the negative electrode plate, and the negative electrode plate is obtained through processes such as drying and cold pressing.

[0054] [Electrolyte] The electrolyte transports ions between the positive and negative electrodes. In some embodiments, the electrolyte comprises an electrolyte salt and an organic solvent. The electrolyte according to this application is selected from ester-based electrolytes, ether-based electrolytes, or aqueous electrolytes. In some embodiments, the electrolyte comprises only an organic solvent.

[0055] In some embodiments, the electrolyte lithium salt is at least one selected from lithium hexafluoride phosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalatoborate, lithium bisoxalatoborate, lithium difluorobis(oxalato)phosphate, and lithium tetrafluoro(oxalato)phosphate.

[0056] In some embodiments, the organic solvent is at least one selected from ethylene carbonate, diethyl carbonate, dimethyl carbonate, or ethylmethyl carbonate.

[0057] In some embodiments, the electrolyte may optionally further contain additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain performance characteristics of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high-temperature performance of the battery, or additives that improve the low-temperature performance of the battery.

[0058] [Separator] In some embodiments, the lithium-ion battery further includes a separator. This application does not particularly limit the type of separator, and any well-known porous separator having good chemical and mechanical stability may be used.

[0059] In some embodiments, the material of the separator is at least one selected from glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multilayer composite film, and is not particularly limited. If the separator is a multilayer composite thin film, the materials of each layer may be the same or different, and is not particularly limited.

[0060] In some embodiments, the positive electrode plate, negative electrode plate, and separator are manufactured as an electrode assembly by a winding process or a lamination process.

[0061] In some embodiments, the lithium-ion battery includes a package, which is used to enclose the electrode assembly and electrolyte.

[0062] In some embodiments, the lithium-ion battery package may be a rigid case, such as a rigid plastic case, an aluminum case, or a steel case, or a soft pack, such as a bag-shaped soft pack. The material of the soft pack can be a plastic, such as polypropylene, polybutylene terephthalate, or polybutylene succinate.

[0063] In this application, the shape of the lithium-ion battery is not particularly limited and may be cylindrical, rectangular, or any other shape. For example, Figure 4 shows a lithium-ion battery 5 with a rectangular structure as an example.

[0064] In some embodiments, as shown in Figure 5, the package includes a housing 51 and a cover plate 53. The housing 51 includes a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a housing chamber. The housing 51 has an opening that communicates with the housing chamber, and the cover plate 53 is provided to close the opening and seal the housing chamber. The positive electrode plate, negative electrode plate and separator are formed as an electrode assembly 52 by a winding process or a lamination process. The electrode assembly 52 is sealed inside the housing chamber. The electrolyte permeates the electrode assembly 52. ​​The number of electrode assemblies 52 included in the lithium-ion battery 5 may be one or more, and can be selected according to the actual requirements of those skilled in the art.

[0065] In some embodiments, lithium-ion batteries can be assembled as battery units, and the number of secondary batteries contained in a battery unit may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery unit.

[0066] Figure 6 shows an example of a battery unit 4. As shown in Figure 6, in the battery unit 4, multiple lithium-ion batteries 5 are arranged sequentially along the length of the battery unit 4. Of course, they may be arranged in any other manner. Furthermore, the multiple lithium-ion batteries 5 may be fixed in place by fixing members. Optionally, the battery unit 4 further comprises a housing having a housing space for accommodating a plurality of lithium-ion batteries 5.

[0067] In some embodiments, the above-described battery unit can be assembled as a battery pack, and the number of battery units included in the battery pack may be one or more, the specific number of which can be selected by those skilled in the art depending on the application and capacity of the battery pack.

[0068] Figures 7 and 8 show an example of a battery pack 1. As shown in Figures 7 and 8, the battery pack 1 comprises a battery box and a plurality of battery units 4 installed in the battery box. The battery box includes an upper box 2 and a lower box 3, with the upper box 2 covering the lower box 3, thereby forming a sealed space for housing the battery units 4. The plurality of battery units 4 are arranged in the battery box in any manner.

[0069] Furthermore, this application provides an electrical device comprising at least one of a lithium-ion battery, battery unit, or battery pack according to this application. The lithium-ion battery, battery unit, or battery pack may be used as a power source for the electrical device or as an energy storage unit for the electrical device. The electrical device includes, but is not limited to, portable devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., fully electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), trains, ships and satellites, and energy storage systems.

[0070] For the aforementioned electrical device, a lithium-ion battery, battery unit, or battery pack can be selected according to the usage requirements.

[0071] Figure 9 shows an example of an electrical device, such as a fully electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high rate and high energy density requirements for lithium-ion batteries in the electrical device, a battery pack or battery unit can be used.

[0072] Other examples of devices include mobile phones, tablets, and laptop computers. Since these devices are generally required to be lightweight and thin, lithium-ion batteries can be used as a power source. [Examples]

[0073] The following describes embodiments of this application. The embodiments described are illustrative and are for interpretation purposes only, and do not limit this application. The absence of specific technical or conditional descriptions in the embodiments can be done in accordance with technical or conditional or product specifications described in the literature in the art. For reagents or instruments whose manufacturers are not specified, commercially available conventional products can be used.

[0074] 1. Manufacturing of lithium-ion batteries (Example 1) 1. Manufacturing of the negative electrode plate (1) The artificial graphite negative electrode active material, the lithium salt LiTFSI surfactant, the conductive agent, and the binder polyvinylidene fluoride (PVDF) were dissolved in N-methylpyrrolidone solvent in a predetermined mass ratio, and the mixture was stirred at 500-700 r / min for 3-4 hours to obtain a uniformly mixed negative electrode slurry. The negative electrode slurry was uniformly applied to both sides of the copper foil for the current collector using a blade, and then dried at a temperature of 85°C for 12 hours. (2) An aqueous solution of a predetermined concentration was prepared using the lithium salt of the surfactant LiTFSI and applied to the surface of the negative electrode plate to prepare the negative electrode functional layer. The negative electrode plate was then dried at a temperature of 85°C for 12 hours. (3) After the cold-pressed negative electrode plate was subjected to edge trimming, sheet cutting, and stripping, it was dried at 110°C under vacuum conditions for 4 hours, tabs were welded, and a negative electrode plate for a lithium-ion battery was manufactured.

[0075] 2. Manufacturing of the positive electrode plate (1) A positive electrode slurry was prepared by dissolving lithium iron phosphate (LiFePO4), a positive electrode active material, LiTFSI, a lithium salt surfactant, Super-P, a conductive agent, and polyvinylidene fluoride (PVDF), a binder, in N-methylpyrrolidone solvent in a mass ratio of 96:2:2 and mixing them uniformly. The positive electrode slurry was uniformly applied to both sides of an aluminum foil current collector and then dried at a temperature of 85°C. (2) LiTFSI, a lithium salt surfactant, was dissolved in NMP to prepare an organic solution of a predetermined concentration, which was then applied to the surface of the positive electrode plate to prepare the positive electrode functional layer. The layer was then dried at a temperature of 85°C for 12 hours to obtain the positive electrode plate. (3) After the positive electrode plate was cold-pressed, the edges were trimmed, the sheet was cut, and the strip was divided. It was then dried at 85°C under vacuum conditions for 4 hours, and tabs were welded to manufacture the positive electrode plate for the lithium-ion battery.

[0076] 3. Preparation of the electrolyte In a glove box under an argon gas atmosphere with a water content of less than 10 ppm, EC, PC, and DMC were mixed by weight in a ratio of EC:PC:DMC = 3:3:3 to obtain a mixed organic solvent. A well-dried lithium salt, LiPF6, was dissolved in the above mixed organic solvent and uniformly stirred to obtain an electrolyte. The concentration of LiPF6 was 1 mol / L.

[0077] 4. Manufacturing of lithium-ion batteries The positive electrode plate, negative electrode plate, and separator (PE film with a ceramic coating layer) of the lithium-ion battery manufactured by the above process were wound together to produce a soft pack core. After filling with liquid, the core was left to stand at high temperature for chemical conversion, and then the capacity was measured.

[0078] (Examples 2-9, Comparative Examples 1-2) The lithium-ion batteries of Examples 2-9 and Comparative Examples 1-2 are similar in manufacturing method to the lithium-ion battery of Example 1, but differ in that the composition of the battery electrode plates and the product parameters have been adjusted.

[0079] (Examples 11-14) In the lithium-ion batteries of Examples 11-14, the active material layer of the electrode plate was laminated (specifically, the coating mass per unit area of ​​the positive electrode first active material sublayer and the negative electrode first active material sublayer was 0.2 g / 1540.25 mm²). 2 The coating mass per unit area of ​​the positive electrode second active material sublayer and the negative electrode second active material sublayer is 0.15 / 1540.25 mm². 2 The dimensions of the electrode plate are 42 x 49.5 mm. 2 This differs from the lithium-ion battery of Example 1 in that it was [details omitted]. In Examples 11 to 14, the lithium salt surfactant LiTFSI was doped into each active material sublayer.

[0080] 2. Performance evaluation of lithium-ion batteries 1. Capacity performance measurement The capacity measurement method used here was the constant current constant voltage method, where the current value and voltage interval were set for measurement. A lithium iron phosphate battery will be used as an example. Step 1: Charge to 3.65V at 0.33C. Step 2: Charge with a constant voltage of 3.65V, with a stop condition of 0.05C. Step 3: Let it stand for 5 minutes. Step 4: Discharge to 0.33C at 2.5V, and after discharge stops, measure the capacity performance data.

[0081] 2. Rate Performance Measurement Step 1: Charge at 0.5C until it reaches 3.65V. Step 2: Charge with a constant voltage of 3.65V, with a stop condition of 0.05C. Step 3: Let it stand for 5 minutes. Step 4: Discharge to 2.5V at 0.5C. Step 5: Repeat Steps 1-4 five times. Step 6: Charge at 0.7C until it reaches 3.65V. Step 7: Charge with a constant voltage of 3.65V, with a stop condition of 0.05C. Step 8: Let it stand for 5 minutes. Step 9: Discharge to 2.5V at 0.7C. Step 10: Repeat steps 6 through 9 five times.

[0082] Following the measurement sequence described above, the measurement current was sequentially increased, and the battery was measured at 1C, 1.2C, 1.5C, and 2C. Five charge-discharge cycles were performed at each current density to obtain rate performance data.

[0083] The parameters and performance measurement data for lithium-ion batteries in Examples 1-14 and Comparative Examples 1-2 are shown in Tables 1 and 2.

[0084] In Tables 1 and 2, the amount of lithium surfactant in the first active material sublayer was denoted as M1, the amount of lithium surfactant in the second active material sublayer as M2, and the amount of lithium surfactant in the functional layer as M3. The total amount of lithium surfactant in the active material layer and functional layer of the electrode plate was denoted as Mp, the amount of lithium salt in the electrolyte was denoted as Ms, and the total volume of the electrolyte was denoted as Vs.

[0085] [Table 1]

[0086] [Table 2]

[0087] Comparing the performance data of lithium-ion batteries from Examples 1 to 9 with that of the lithium-ion battery from Comparative Example 1, it was found that in Examples 1 to 9, lithium surfactant salts were added to the active material layer and functional layer on the surface of the electrode plate. By utilizing the affinity between the lithium surfactant salts and the electrolyte, the surface tension of the electrolyte was effectively reduced, improving the wettability of the electrolyte to the electrode plate. As a result, both the discharge capacity and rate performance of the lithium-ion batteries were significantly better than those of Comparative Example 1, in which lithium surfactant salts were not added to the surface of the electrode plate.

[0088] Comparing the performance data of lithium-ion batteries from each of Examples 1 to 5 with that of the lithium-ion battery from Comparative Example 2, when Mp is the total amount of lithium salt surfactant in the active material layer and functional layer of the electrode plate, Ms is the amount of lithium salt in the electrolyte, and Vs is the total volume of the electrolyte, if (Mp + Ms) / Vs is 1 to 2 mol / L, then the doping concentration of lithium salt surfactant on the electrode plate was within an appropriate range. This contributes to the wettability of the electrolyte to the electrode plate, does not impair ionic conductivity, does not increase the polarization of the battery, and guarantees the overall electrochemical performance of the lithium-ion battery.

[0089] In Examples 6-9, the amount of lithium electrolyte salt in the electrolyte (Ms) was 0. When the electrolyte does not contain lithium electrolyte salt, the electrolyte solvent is directly injected into the battery as the electrolyte. After the electrolyte solvent permeates the electrode plate, the lithium surfactant salt on the electrode plate dissolves in the electrolyte, thereby enabling ion transport. When a pure solvent is injected into the battery as the electrolyte, the viscosity of the pure solvent is relatively low, resulting in better wettability to the electrode plate. Subsequently, after the lithium surfactant salt doped onto the electrode plate dissolves, pore formation in the electrode is further realized, creating a porous electrode. This further improves the wettability of the electrolyte to the electrode plate. For this reason, the lithium-ion batteries according to Examples 6-9 exhibited relatively good capacity performance and rate performance.

[0090] In Examples 10-14, the active material layer of the lithium-ion battery contained two active material sublayers with different coating masses per unit area, and the lithium salt surfactant was doped into each active material sublayer and surface functional layer in a reasonable proportion, which better fulfilled the pore formation role, resulting in lithium-ion batteries with relatively good capacity performance and rate performance.

[0091] This application is not limited to the embodiments described above. The embodiments described above are merely illustrative, and embodiments that have substantially the same configuration as the technical concept and can achieve similar effects within the scope of the technical idea of ​​this application also fall within the scope of this application. Furthermore, various modifications to the embodiments that can be conceived by a person skilled in the art, as long as they do not depart from the spirit of this application, and other methods formed by combining some of the components of the embodiments also fall within the scope of this application. [Explanation of Symbols]

[0092] 1 Battery pack 2 Upper box 3 Lower box 4 Battery Unit 5. Lithium-ion battery 51 Housing 52 Electrode Assembly 53 Cover Plate

Claims

1. Lithium-ion battery, It includes a positive electrode plate, a negative electrode plate, a separator installed between the positive electrode plate and the negative electrode plate, and an electrolyte. At least one of the positive electrode plate and the negative electrode plate comprises a current collector and an active material layer provided on at least one surface of the current collector, wherein the active material layer contains a lithium salt surfactant. A lithium salt surfactant layer is provided on the surface of the active material layer that is spaced apart from the current collector, and the lithium salt surfactant layer also contains the lithium salt surfactant. In the active material layer and the lithium salt surfactant layer of at least one of the positive electrode plate and the negative electrode plate, when the total amount of substance of the lithium salt surfactant is Mp, the amount of substance of the lithium salt in the electrolyte is Ms, and the total volume of the electrolyte is Vs, in the lithium-ion battery, (Mp + Ms) / Vs is 1 to 2 mol / L. The solvent in the electrolyte is at least one selected from ethylene carbonate, propylene carbonate, and dimethyl carbonate. A lithium-ion battery characterized by the following features.

2. The aforementioned lithium surfactant salt is at least one selected from lithium bis(trifluoromethanesulfonyl)imide, lithium nitrate, lithium perchlorate, and lithium chloride. The lithium-ion battery according to feature 1.

3. The amount of the lithium salt surfactant in the active material layer is 0.00175 to 0.00875 mol. The lithium-ion battery according to feature 1.

4. The active material layer includes several active material sublayers stacked in an order of increasing coating mass per unit area along a direction away from the current collector, and the amount of the lithium salt surfactant contained in these active material sublayers also changes in increasing order. The lithium-ion battery according to feature 1.

5. The active material layer includes a first active material sublayer and a second active material sublayer that are stacked sequentially along a direction away from the current collector. Let CW1 be the coating mass per unit area of ​​the first active material sublayer, where CW1 is 0.150 g / 1540.25 mm ２ ≦CW1≦0.200g / 1540.25mm ２ The following conditions are met, and the coating mass per unit area of ​​the second active material sublayer is CW2, where CW2 ≥ 0.200 g / 1540.25 mm ２ Satisfying the conditions, When the amount of the lithium surfactant in the first active material sublayer is M1, the amount of the lithium surfactant in the second active material sublayer is M2, and the amount of the lithium surfactant in the lithium surfactant layer is M3, M1 / (M1+M2+M3) is between 10% and 30%. M2 / (M1+M2+M3) is between 20% and 40%. M3 / (M1+M2+M3) is between 30% and 70%. The lithium-ion battery according to feature 4.

6. (Mp + Ms) / Vs is 1 mol / L The lithium-ion battery according to feature 1.

7. Includes a lithium-ion battery according to any one of claims 1 to 6 A battery unit characterized by the following features.

8. Includes the battery unit described in claim 7 A battery pack characterized by the following features.

9. Includes the battery pack described in claim 8 An electrical device characterized by the following features.

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