Lithium ion battery, preparation method thereof and power utilization device

Abstract

The embodiment of the invention discloses a lithium ion battery, a preparation method thereof and a power utilization device. The lithium ion battery comprises a negative pole piece, and a negative active material layer of the negative pole piece comprises lithium-loving metal; the electrolyte comprises metal ions, and the reduction potential of the metal ions is higher than that of the lithium ions. Lithium-loving metal and metal ions in the lithium ion battery can continuously inhibit lithium dendrites in the long-cycle process, so that the cycle performance of the lithium ion battery is effectively improved, and the service life of the lithium ion battery is effectively prolonged.

Description

Technical Field

[0001] The present application relates to the field of batteries, and more specifically, to a lithium-ion battery and a preparation method and an electrical device thereof. Background Art

[0002] In recent years, lithium-ion batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power and solar power stations, as well as power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace and other fields, and have thus achieved great development.

[0003] Lithium dendrites are one of the factors that affect the performance of lithium-ion batteries. The growth of lithium dendrites will lead to a decrease in battery coulombic efficiency and poor cycle performance. In severe cases, they will puncture the diaphragm and cause a short circuit in the battery. Therefore, how to inhibit the growth of lithium dendrites is a technical problem that needs to be solved urgently. Summary of the invention

[0004] The present application is made in view of the above technical problems, and its purpose is to provide a lithium ion battery and its preparation method and electrical device. The lithium ion battery has a designed negative electrode plate and electrolyte, which can effectively improve the lithium precipitation during the battery cycle, thereby inhibiting lithium dendrites.

[0005] In a first aspect, a lithium-ion battery is provided, comprising: a negative electrode plate, wherein the negative electrode active material layer of the negative electrode plate comprises a lithium-philic metal; and an electrolyte, wherein the electrolyte comprises metal ions, wherein the reduction potential of the metal ions is higher than the reduction potential of lithium ions.

[0006] It should be understood that a lithiophilic metal is a metal element that is capable of forming an alloy with lithium.

[0007] In an embodiment of the present application, there is a lithium-philic metal in the negative electrode plate of the lithium-ion battery, and there are metal ions in the electrolyte. Among them, the lithium-philic metal can form a lithium-metal alloy with lithium when lithium is precipitated at the negative electrode, and the reduction potential of the metal corresponding to the metal ion is higher than the reduction potential of lithium. When lithium is precipitated at the negative electrode, the metal ion can be reduced to a metal element by lithium, consuming the precipitated lithium. Thus, by using a negative electrode plate containing a lithium-philic metal and an electrolyte containing metal ions, the lithium precipitation problem during the cycle of the lithium-ion battery can be effectively improved, thereby inhibiting the generation and / or growth of lithium dendrites. Moreover, through the joint action of the lithium-philic metal and the metal ions, the continuous suppression of lithium dendrites can be achieved during the long cycle of the lithium-ion battery, thereby helping to improve the cycle performance and service life of the lithium-ion battery.

[0008] In a possible implementation, the lithium-philic metal is located on a surface of the negative electrode active material layer close to the electrolyte.

[0009] Lithium deposition usually occurs on the surface of the negative electrode active material layer. In the embodiment of the present application, by arranging a lithium-philic metal on the surface of the negative electrode active material layer close to the electrolyte, it is helpful to consume the deposited lithium in time when lithium deposition occurs at the negative electrode, thereby more effectively improving lithium deposition and inhibiting lithium dendrites.

[0010] In one possible implementation, the lithium-philic metal includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0011] In a possible implementation, the content w1 of the lithium-philic metal in the negative electrode plate satisfies: 100 ppm≤w1≤1000 ppm.

[0012] The content of the lithium-philic metal in the negative electrode sheet affects both the inhibition effect of lithium dendrites and the impedance of the battery. In the embodiments of the present application, by controlling the content of the lithium-philic metal within a suitable range, it helps to improve the impedance of the lithium-ion battery while inhibiting lithium dendrites.

[0013] In a possible implementation, the lithium-philic metal includes single atoms and / or particles, and the size d of the particles satisfies: 0 nm<d≤3 nm.

[0014] In the case where the negative electrode active material layer contains a lithium-philic metal, the lithium-philic metal has a certain influence on the physical and chemical properties of the SEI film formed on the surface of the negative electrode active material layer. In the embodiments of the present application, by controlling the particle size of the lithium-philic metal within a suitable range, the possibility of excessive self-discharge of the lithium-ion battery due to the inability of the SEI film to insulate can be reduced, thereby helping to increase the service life of the lithium-ion battery.

[0015] In a possible implementation, the SEI film of the negative electrode plate includes at least one of the fluorides and carbonates of the lithium-philic metal.

[0016] In a possible implementation, the metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

[0017] In a possible implementation, the content w2 of the metal ions in the electrolyte satisfies: 500ppm≤w2≤50000ppm; optionally, 2000ppm≤w2≤20000ppm.

[0018] The content of metal ions in the electrolyte affects both the inhibition effect of lithium dendrites and the impedance of the electrolyte. In the embodiments of the present application, by controlling the content of metal ions in the electrolyte within a suitable range, it helps to improve the impedance of the lithium-ion battery while inhibiting lithium dendrites.

[0019] In a possible implementation, the electrolyte includes an inorganic salt, and the inorganic salt includes the metal ion and an anion; the anion includes at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonyl imide anions.

[0020] In a possible implementation, the lithium-philic metal is obtained by a chemical reaction.

[0021] In a possible implementation, the chemical reaction includes atomic layer deposition, liquid phase deposition, and solid phase deposition.

[0022] In a possible implementation, the lithium-philic metal is obtained by an electrochemical reaction.

[0023] In a second aspect, a lithium-ion battery is provided, comprising: a negative electrode plate, wherein the negative electrode active material layer of the negative electrode plate comprises a lithium-metal alloy; and an electrolyte, wherein the electrolyte comprises metal ions, and the reduction potential of the metal ions is higher than the reduction potential of lithium ions.

[0024] In a possible implementation, the negative electrode active material layer includes a lithium-philic metal, and the lithium-metal alloy includes an alloy formed by lithium and the lithium-philic metal.

[0025] In a possible implementation, the lithium-metal alloy further includes an alloy formed by lithium and a metal obtained by reducing the metal ions.

[0026] In a possible implementation, the lithium-metal alloy is located on a surface of the negative electrode active material layer close to the electrolyte.

[0027] In a possible implementation, the content w3 of the lithium-philic metal in the negative electrode plate satisfies: 100 ppm≤w3≤3000 ppm.

[0028] In one possible implementation, the metal in the lithium-metal alloy includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0029] In a possible implementation, the metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

[0030] In a possible implementation, the content w4 of the metal ions in the electrolyte satisfies: 100 ppm≤w4≤48000 ppm; optionally, 300 ppm≤w4≤19000 ppm.

[0031] In a third aspect, a method for preparing a lithium-ion battery is provided, the method comprising: preparing a lithium-philic metal in a negative electrode active material layer of a negative electrode plate; adding metal ions into an electrolyte, wherein the reduction potential of the metal ions is higher than the reduction potential of lithium ions; and assembling the negative electrode plate and the electrolyte into the lithium-ion battery.

[0032] In a possible implementation, the preparing the lithium-philic metal in the negative electrode active material layer of the negative electrode plate includes: preparing the lithium-philic metal on the surface of the negative electrode active material layer close to the electrolyte.

[0033] In a possible implementation, the preparing the lithium-philic metal in the negative electrode active material layer of the negative electrode plate includes: preparing the lithium-philic metal by chemical reaction.

[0034] In a possible implementation, the chemical reaction includes atomic layer deposition, liquid phase deposition, and solid phase deposition.

[0035] In a possible implementation, the preparing the lithium-philic metal in the negative electrode active material layer of the negative electrode plate includes: preparing the lithium-philic metal by an electrochemical reaction.

[0036] In a possible implementation, the electrochemical reaction includes: reducing the metal ions at a reduction potential of the metal ions to obtain the lithium-philic metal.

[0037] In a possible implementation, the SEI film of the negative electrode plate includes at least one of the fluorides and carbonates of the lithium-philic metal.

[0038] In a possible implementation, the adding of metal ions into the electrolyte comprises: adding an inorganic salt into the electrolyte, wherein the inorganic salt comprises the metal ions and anions, and the anions comprise at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonimide anions.

[0039] In one possible implementation, the lithium-philic metal includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0040] In a possible implementation, the metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

[0041] In a fourth aspect, an electrical device is provided, comprising at least one of the lithium-ion battery in any possible implementation of the first aspect, the lithium-ion battery in any possible implementation of the second aspect, and the lithium-ion battery prepared by the method in any possible implementation of the third aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the drawings without paying creative work.

[0043] Figure 1 The present invention is a schematic flow chart of a method for preparing a lithium-ion battery.

[0044] Figure 2 A schematic diagram of a battery cell.

[0045] Figure 3 A schematic diagram of a battery module.

[0046] Figure 4 A schematic diagram of a battery.

[0047] Figure 5 Another schematic diagram of a battery. DETAILED DESCRIPTION

[0048] Hereinafter, the lithium-ion battery of the present application, its preparation method, and the implementation mode of the electric device thereof will be specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there may be cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0049] "Scope" disclosed in the present application is limited in the form of lower limit and upper limit, and a given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a special range. The scope limited in this way can be including end values ​​or not including end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a scope. For example, if the scope of 60-120 and 80-110 is listed for a specific parameter, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following scope can be all expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, the numerical range "ab" represents the abbreviation of any real number combination between a and b, wherein a and b are real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0050] In the description of the present application, it should be noted that, unless otherwise specified, "multiple" means more than two; the directions or positional relationships indicated by the terms "upper", "lower", "left", "right", "inner", "outer", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0051] If not otherwise specified, in this application, the phrase "A and / or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A and / or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0052] If there is no special explanation, all steps of the present application can be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, the method may further include step (c), which means that step (c) may be added to the method in any order. For example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0053] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0054] Unless otherwise specified, the following terms have the following meanings. Any undefined terms have their generally accepted meanings in the art.

[0055] As mentioned, "lithiophilic metal" refers to a metal element that can form a lithium-metal alloy with lithium, such as magnesium, zinc, aluminum, etc.

[0056] Where mentioned, “lithium dendrites” refer to the dendritic lithium metal that forms when lithium ions are reduced during the cycling process of lithium-ion batteries.

[0057] If mentioned, "SEI film" refers to the solid electrolyte interface (SEI) film. The SEI film is a passivation film formed on the surface of the negative electrode by lithium ions and some components in the electrolyte during the charging process of the lithium-ion battery.

[0058] Where mentioned, "particles" refers to nano-sized particles formed by the aggregation of multiple atoms or molecules.

[0059] Next, embodiments of the present application are introduced.

[0060] In recent years, secondary batteries have been widely used in power tools, electronic products, electric vehicles, aerospace and other fields due to their high energy density and long service life, and have achieved great development. Usually, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte and a separator. During the charge and discharge process of the battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. Among them, the electrolyte plays a role in conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, which allows active ions to pass through while preventing the positive and negative electrodes from short-circuiting, so that the electrochemical reaction of the secondary battery proceeds normally.

[0061] Take lithium-ion batteries as an example. Lithium-ion batteries are a typical secondary battery. Because they rely on the chemical reaction of lithium ions intercalating and disintercalating between the positive and negative electrodes for charging and discharging, lithium-ion batteries are also called rocking-chair batteries. During the charging process of lithium-ion batteries, lithium ions are released from the positive electrode active material, move to the negative electrode through the conduction of the electrolyte and embed into the negative electrode active material; and during the discharge process, lithium ions are released from the negative electrode active material, move to the positive electrode through the conduction of the electrolyte and embed into the positive electrode active material.

[0062] It should be understood that the "lithium insertion" and "embedding" processes described in this application refer to the process in which lithium ions are embedded in the positive electrode active material or the negative electrode active material due to an electrochemical reaction, and the "extraction", "delithium" and "extraction" processes described in this application refer to the process in which lithium ions are extracted from the positive electrode active material or the negative electrode active material due to an electrochemical reaction.

[0063] During the charge and discharge process of lithium-ion batteries, factors such as the change in the internal resistance of lithium-ion batteries, the balance between the speed of electrochemical reactions at the positive and negative electrodes and the speed of electron movement, and the diffusion rate of lithium ions involved in the electrochemical reaction will lead to the polarization of the battery, causing lithium ions to precipitate from the surface of the negative electrode active material layer, i.e., lithium deposition. With the further deposition of lithium ions, the formation and growth of lithium dendrites may occur. The formation and growth of lithium dendrites will continuously consume lithium ions, resulting in the attenuation of the battery's capacity and cycle life; in severe cases, lithium dendrites may also pierce the separator, causing a short circuit between the positive and negative electrodes, causing battery safety problems.

[0064] In view of this, the embodiments of the present application provide a lithium-ion battery and a preparation method thereof, and an electrical device, wherein the lithium-ion battery has a negative electrode plate including a lithium-philic metal and an electrolyte including metal ions, and both the lithium-philic metal and the metal ions can improve lithium precipitation during the cycle of the lithium-ion battery, thereby inhibiting the formation of lithium dendrites, thereby achieving the inhibition of lithium dendrites during the long cycle of the lithium-ion battery.

[0065] Generally, a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. Next, the lithium-ion battery provided in the present application and various parts of the lithium-ion battery are introduced.

[0066] First, a lithium-ion battery is provided, which includes a negative electrode plate and an electrolyte, wherein the negative electrode active material layer of the negative electrode plate includes a lithium-philic metal; and the electrolyte includes metal ions, the reduction potential of which is higher than the reduction potential of lithium ions.

[0067] Specifically, during the cycle of the lithium-ion battery, when lithium deposition occurs on the surface of the negative electrode active material layer, the lithium-philic metal in the negative electrode active material layer can react with the deposited lithium to form a lithium-metal alloy, which preliminarily inhibits lithium deposition. During the high current cycle or long cycle of the lithium-ion battery, the inhibitory effect of the lithium-philic metal in the negative electrode active material layer is limited, and lithium dendrites may continue to grow and pierce the SEI film. Since the reduction potential of the metal ions in the electrolyte is higher than the reduction potential of the lithium ions, the metal ions can be reduced to metal elements by the deposited lithium, consuming the deposited lithium. In this way, the continuous inhibition of lithium dendrites is achieved during the long cycle of the lithium-ion battery.

[0068] It should be understood that the elements of the lithiophilic metal and the metal ion may be the same or different.

[0069] This embodiment introduces lithium-philic metals into the negative electrode active material layer of the lithium-ion battery and metal ions into the electrolyte, which can effectively inhibit the formation and / or growth of lithium dendrites and improve the safety performance and service life of the battery during the long cycle process of the battery.

[0070] In one embodiment, the lithium-philic metal is located on the surface of the negative electrode active material layer close to the electrolyte.

[0071] Specifically, lithium precipitation usually occurs on the surface of the negative electrode active material layer. In this embodiment, by introducing a lithium-philic metal on the surface of the negative electrode active material layer close to the electrolyte, the lithium-philic metal is helped to react with the precipitated lithium in a timely manner to form a lithium-metal alloy, thereby helping to improve the inhibitory effect of the lithium-philic metal on lithium precipitation.

[0072] For example, in the process of preparing the negative electrode active material layer including the lithium-philic metal, the content of the lithium-philic metal on the surface of the negative electrode active material layer can be controlled to be higher than the content of the lithium-philic metal in the negative electrode active material layer near the current collector.

[0073] In one embodiment, the lithium-philic metal includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0074] In one embodiment, the content w1 of the lithium-philic metal in the negative electrode sheet satisfies: 100 ppm≤w1≤1000 ppm.

[0075] Specifically, w1 can be 100 ppm, 200 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 700 ppm, 800 ppm, 900 ppm, 1000 ppm, or a numerical range within the range obtained by combining any two of the above numerical values.

[0076] On the one hand, if the content of the lithium-philic metal is too low, the inhibitory effect of the lithium-philic metal on lithium precipitation is limited, so that local lithium precipitation may occur in the negative electrode active material layer. On the other hand, if the content of the lithium-philic metal is too high, the lithium-philic metal covers too much of the surface of the negative electrode active material layer, and more alloys are formed, which increases the impedance of the lithium-ion battery, and the lithium-philic metal cannot contribute to the capacity of the lithium-ion battery, which is not conducive to improving the energy density of the lithium-ion battery. In one possible implementation, the lithium-philic metal is prepared by an electrochemical reaction. Specifically, the lithium-philic metal can be prepared by electrochemical reduction of metal ions in an electrolyte. In the process of electrochemical reduction, illustratively, the content of the lithium-philic metal in the negative electrode active material layer can be regulated by controlling the concentration of metal ions in the electrolyte.

[0077] Therefore, this embodiment can effectively suppress lithium deposition while reducing the influence of the lithium-philic metal on the impedance of the lithium-ion battery by controlling the content w1 of the lithium-philic metal in the negative electrode plate within a suitable range.

[0078] In one embodiment, the lithium-philic metal includes single atoms and / or particles, and the size d of the particles satisfies: 0 nm<d≤3 nm.

[0079] Specifically, d can be 0.1nm, 0.2nm, 0.3nm, 0.4nm, 0.5nm, 0.6nm, 0.7nm, 0.8nm, 0.9nm, 1nm, 1.1nm, 1.2nm, 1.3nm, 1.4nm, 1.5nm, 1.6nm, 1.7nm, 1.8nm, 1.9nm, 2.0nm, 2.1nm, 2.2nm, 2.3nm, 2.4nm, 2.5nm, 2.6nm, 2.7nm, 2.8nm, 2.9nm, 3.0nm, or its numerical range is within the range obtained by combining any two of the above numerical values.

[0080] Since the lithium-philic metal is conductive, if the size of the lithium-philic metal is too large, the insulation of the SEI film on the surface of the negative electrode active material layer may decrease, thereby increasing the self-discharge of the lithium-ion battery, affecting the capacity and service life of the lithium-ion battery. In a possible implementation, the lithium-philic metal is prepared by an electrochemical reaction, and in the process of electrochemical reduction, the particle size of the lithium-philic metal can be regulated by controlling the time of the electrochemical reaction.

[0081] In this embodiment, the size of the lithium-philic metal is controlled within a smaller range, which can reduce the impact on the insulation of the SEI film formed on the surface of the negative electrode active material layer after the lithium-philic metal is introduced into the negative electrode active material layer, thereby helping to reduce the self-discharge of the lithium-ion battery.

[0082] The lithium-philic metal includes single atoms, which can be understood as the morphology of the lithium-philic metal being a single metal atom. The lithium-philic metal includes particles, which can be understood as the morphology of the lithium-philic metal being an aggregation of multiple metal atoms.

[0083] In one embodiment, the SEI film of the negative electrode sheet includes at least one of lithium-philic metal fluorides and carbonates.

[0084] In one embodiment, the metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

[0085] Specifically, during the long cycle of lithium-ion batteries, when the lithium-philic metal in the negative electrode is consumed in large quantities and can no longer suppress lithium precipitation, the above-mentioned metal ions can be reduced by lithium to form metal elements, and the metal elements are lithium-philic and can continue to form lithium-metal alloys with lithium. The lithium-metal alloy can further induce the uniform deposition of lithium on the negative electrode, regulate the morphology of the surface of the negative electrode, and thus suppress the growth of lithium dendrites, which helps to improve the cycle performance and service life of lithium-ion batteries during long cycles.

[0086] In another embodiment, after the metal ions are reduced to a metal element by lithium, the metal element may not be lithiophilic. In other words, the metal element may not form a lithium-metal alloy with lithium.

[0087] In one embodiment, the content w2 of the metal ions in the electrolyte satisfies: 500ppm≤w2≤50000ppm; optionally, 2000ppm≤w2≤20000ppm.

[0088] Specifically, w2 can be 500ppm, 1000ppm, 1500ppm, 2000ppm, 2500ppm, 3000ppm, 3500ppm, 4000ppm, 4500ppm, 5000ppm, 5500ppm, 6000ppm, 6500ppm, 7000ppm, 7500ppm, 8000ppm, 8500ppm, 9000ppm, 9500ppm, 10000ppm, 15000ppm, 20000ppm, 25000ppm, 30000ppm, 35000ppm, 40000ppm, 45000ppm, 50000ppm, or its numerical range is within the range obtained by combining any two of the above numerical values.

[0089] On the one hand, if the metal ion content in the electrolyte is too low, the inhibitory effect on lithium precipitation is limited; on the other hand, if the metal ion content in the electrolyte is too high, the viscosity of the electrolyte will be too high and the impedance of the lithium-ion battery will increase.

[0090] In this embodiment, by controlling the content of metal ions in the electrolyte within a suitable range, it is helpful to suppress lithium dendrites while reducing the effect of metal ions on the impedance of the lithium-ion battery.

[0091] In one embodiment, the electrolyte includes an inorganic salt, and the inorganic salt includes the metal ion and an anion; the anion includes at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonimide anions.

[0092] In one embodiment, the lithiophilic metal is obtained by chemical reaction.

[0093] In one embodiment, the chemical reaction includes atomic layer deposition (ALD), liquid phase deposition (LPD), and solid phase deposition (SP).

[0094] In one embodiment, the lithiophilic metal is obtained by an electrochemical reaction.

[0095] In the above embodiment, a lithium ion battery capable of suppressing lithium dendrites for a long time is introduced. Next, the lithium ion battery after the above lithium ion battery has been cycled is introduced.

[0096] The embodiment of the present application also provides a lithium-ion battery after cycling, comprising a negative electrode plate and an electrolyte, wherein the negative electrode active material layer of the negative electrode plate comprises a lithium-metal alloy, and the electrolyte comprises metal ions, and the reduction potential of the metal ions is higher than the reduction potential of the lithium ions.

[0097] It should be understood that in the embodiments of the present application, the lithium-ion battery after cycling can be considered as a lithium-ion battery in which lithium deposition has occurred, that is, a lithium-ion battery after lithium deposition. As mentioned in the aforementioned embodiments, the negative electrode plate of the lithium-ion battery includes a lithium-philic metal, and the electrolyte includes metal ions. Therefore, lithium is deposited on the surface of the negative electrode active material layer of the lithium-ion battery after cycling, and the deposited lithium is consumed by the lithium-philic metal and / or metal ions, so that the negative electrode active material layer of the lithium-ion battery after cycling includes a lithium-metal alloy.

[0098] In one embodiment, the negative electrode active material layer includes a lithium-philic metal, and the lithium-metal alloy includes an alloy formed of lithium and the lithium-philic metal.

[0099] Specifically, when lithium is just beginning to precipitate on the surface of the negative electrode active material layer, the precipitated lithium can react with the lithium-philic metal in the negative electrode active material layer to form a lithium-metal alloy. Thus, the negative electrode active material layer of the cycled lithium-ion battery includes a lithium-metal alloy formed by the lithium-philic metal and the precipitated lithium.

[0100] In one embodiment, the lithium-metal alloy further includes an alloy formed by lithium and a metal obtained by reducing a metal ion.

[0101] For example, during the long cycle of a lithium-ion battery, the content of the lithium-philic metal in the negative electrode active material layer is limited. When the lithium-philic metal in the negative electrode active material layer can no longer improve lithium precipitation and inhibit the growth of lithium dendrites, lithium dendrites may continue to grow. In the case where lithium dendrites pierce the SEI film on the surface of the negative electrode active material layer, the free metal ions in the electrolyte can diffuse to the lithium dendrites and be reduced to metal elements by lithium, and then react with lithium to form lithium-metal alloys. As a result, the negative electrode active material layer of the cycled lithium-ion battery may also include a lithium-metal alloy formed by the metal obtained by the reduction of the metal ions and lithium. In other words, the metal elements obtained by the reduction of the metal ions in the electrolyte can also participate in the formation of the lithium-metal alloy.

[0102] It should be understood that in the case where the lithium-loving metal and the metal ion have the same element, the lithium-metal alloy in the negative electrode active material layer after cycling can be a single-component alloy. Exemplarily, the lithium-loving metal is zinc (Zn), and the metal ion is zinc ion (Zn 2+ ), then the composition of the lithium-metal alloy is a lithium-zinc alloy. In the case where the lithium-philic metal and the metal ion are different elements, the lithium-metal alloy in the negative electrode active material layer after cycling can be a multi-component alloy. Exemplarily, the lithium-philic metal is zinc (Zn), and the metal ion is magnesium ion (Mg 2+ ), then the composition of the lithium-metal alloy can include both lithium-zinc alloy and lithium-magnesium alloy.

[0103] In one embodiment, the lithium-metal alloy is located on the surface of the negative electrode active material layer close to the electrolyte.

[0104] Specifically, in the case where the lithium-philic metal is located on the surface of the negative electrode active material layer, in the cycled lithium-ion battery, the lithium-metal alloy is also located on the surface of the negative electrode active material layer close to the electrolyte.

[0105] In one embodiment, the content w3 of the lithium-philic metal in the negative electrode sheet satisfies: 100 ppm≤w3≤3000 ppm.

[0106] Specifically, w3 can be 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2600ppm, 2800ppm, 3000ppm, or its numerical range is within the range obtained by combining any two of the above numerical values.

[0107] In one embodiment, the metal in the lithium-metal alloy includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0108] In one embodiment, the metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

[0109] In one embodiment, the content w4 of the metal ions in the electrolyte satisfies: 100ppm≤w4≤48000ppm; optionally, 300ppm≤w4≤19000ppm.

[0110] As the number of cycles of lithium-ion batteries increases, the content of metal ions in the electrolyte will gradually decrease. Exemplarily, when lithium ions just begin to precipitate lithium, the content of metal ions in the electrolyte w4 satisfies 400ppm≤w4≤48000ppm, optionally, 1800ppm≤w4≤19000ppm. As the metal ions are gradually consumed by lithium dendrites, the content of metal ions in the electrolyte w4 satisfies: 100ppm≤w4≤42000ppm, optionally, 300ppm≤w4≤14000ppm.

[0111] Specifically, W4 can be 100ppm, 200ppm, 300ppm, 400ppm, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm, 6000ppm, 7000ppm, 8000ppm, 9000ppm, 10000ppm, 11000ppm, 12000ppm, 13000ppm, 14000ppm, 15000ppm , 16000ppm, 17000ppm, 18000ppm, 19000ppm, 20000ppm, 22000ppm, 24000ppm, 26000ppm, 28000ppm, 30000ppm, 32000ppm, 34000ppm, 36000ppm, 38000ppm, 40000ppm, 42000ppm, 44000ppm, 46000ppm, 48000ppm, or a numerical range within the range obtained by combining any two of the above numerical values.

[0112] Next, the positive electrode sheet, negative electrode sheet, separator and electrolyte in the lithium-ion battery are introduced in detail.

[0113] [Negative electrode]

[0114] The negative electrode sheet generally includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material and a lithium-philic metal.

[0115] As an example, the negative electrode current collector has two surfaces opposite to each other in the thickness direction thereof, 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. The negative electrode active material layer disposed on the surface of the negative electrode current collector also has two opposite surfaces in the thickness direction thereof, and one of the surfaces is in contact with the negative electrode current collector, and the other surface is away from the negative electrode current collector along the thickness direction of the negative electrode active material layer. The "surface of the negative electrode active material layer close to the electrolyte" mentioned in the embodiments of the present application is the surface of the negative electrode active material layer away from the negative electrode current collector.

[0116] In one embodiment, the negative electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, 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 the 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.).

[0117] In one embodiment, the negative electrode active material may adopt the negative electrode active material for batteries known in the art. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0118] In one embodiment, the lithium-philic metal may be a metal known in the art that can form an alloy with lithium. As an example, the lithium-philic metal may be selected from at least one of the following metals: Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0119] In one embodiment, the content w1 of the lithium-philic metal in the negative electrode active material layer satisfies: 100 ppm≤w1≤1000 ppm.

[0120] In one embodiment, the lithium-philic metal includes single atoms and / or particles, and the size d of the particles satisfies: 0 nm<d≤3 nm.

[0121] In one embodiment, the negative electrode active material layer further includes a binder. The binder can 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).

[0122] In one embodiment, the negative electrode active material layer further includes 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.

[0123] In one embodiment, the negative electrode active material layer further includes other additives, such as a thickener (eg sodium carboxymethyl cellulose (CMC-Na)).

[0124] In one embodiment, the negative electrode sheet can be prepared in the following manner: the components for preparing the negative electrode sheet are formed into a negative electrode slurry. For example, the negative electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a negative electrode slurry. Then, the negative electrode slurry is coated on the negative electrode current collector, and after drying, rolling and other processes, the negative electrode sheet can be obtained.

[0125] [Positive electrode]

[0126] The positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector.

[0127] As an example, the positive electrode current collector has two surfaces facing each other in its thickness direction, and the positive electrode active material layer is disposed on any one or both of the two facing surfaces of the positive electrode current collector.

[0128] In one embodiment, the positive electrode current collector may be a metal foil or a composite current collector. For example, as the metal foil, 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 (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0129] In one embodiment, the positive electrode active material may adopt a positive electrode active material for a battery that is well known in the art. As an example, the positive electrode active material may include at least one of the following materials: a lithium-containing phosphate with an olivine structure, a lithium transition metal oxide, and their respective modified compounds. However, the present application is not limited to these materials, and other traditional materials that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxide (such as LiCoO2), lithium nickel oxide (such as LiNiO2), lithium manganese oxide (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide (such as LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM333), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM523), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM211), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM622), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM811), lithium nickel cobalt aluminum oxide (such as LiNi 0.85 Co 0.15 Al 0.05 O2) and at least one of its modified compounds. Examples of lithium-containing phosphates with an olivine structure may include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), a composite material of lithium iron phosphate and carbon, lithium manganese phosphate (such as LiMnPO4), a composite material of lithium manganese phosphate and carbon, lithium iron manganese phosphate, and at least one of a composite material of lithium iron manganese phosphate and carbon. The battery is accompanied by the deintercalation and consumption of Li during the charging and discharging process, and the molar content of Li in the positive electrode active material is different when the battery is discharged to different states. In the enumeration of positive electrode active materials in this application, the molar content of Li is the initial state of the material, that is, the state before feeding. The positive electrode active material is used in the battery system, and the molar content of Li will change after charge and discharge cycles. In the enumeration of positive electrode active materials in this application, the molar content of O is only an ideal state value. The release of lattice oxygen will cause the molar content of O to change, and the actual molar content of O will fluctuate.

[0130] In one embodiment, the positive electrode active material layer further includes a binder. As an example, the binder may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin.

[0131] In one embodiment, the positive electrode active material layer further includes a conductive agent. As an example, the conductive agent may include at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0132] In one embodiment, the positive electrode sheet can be prepared in the following manner: the components for preparing the positive electrode sheet are respectively formed into positive electrode slurries. For example, the positive electrode active material, the conductive agent, the binder and any other components are dispersed in a solvent (such as N-methylpyrrolidone) to form a positive electrode slurry. Then, the positive electrode slurry is coated on the positive electrode current collector, and after drying, rolling and other processes, the positive electrode sheet can be obtained.

[0133] [Electrolyte]

[0134] The electrolyte plays a role in conducting ions between the positive electrode and the negative electrode. The present application has no specific restrictions on the type of electrolyte, which can be selected according to needs. The electrolyte includes electrolyte salts, solvents and metal ions.

[0135] In one embodiment, the electrolyte 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.

[0136] In one embodiment, the solvent can be selected from at least one of ethylene carbonate, propylene carbonate, ethyl methyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butylene carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, cyclopentane sulfone, dimethyl sulfone, methyl ethyl sulfone and diethyl sulfone.

[0137] In one embodiment, the metal ions are provided by inorganic salts. In other words, the electrolyte includes inorganic salts, and the inorganic salts include the metal ions and anions. The metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ The anion includes at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonyl imide anions.

[0138] In one embodiment, the electrolyte may further include additives, which may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain performance of the battery, such as additives that improve the overcharge performance of the battery, additives that improve the high or low temperature performance of the battery, etc.

[0139] [Isolator]

[0140] In one embodiment, the battery further includes a separator. The present application has no particular limitation on the type of separator, for example, any known porous structure separator with good chemical stability and mechanical stability can be selected.

[0141] In one embodiment, the material of the isolation membrane can be selected from at least one of glass fiber, non-woven fabric, polyethylene, polypropylene and polyvinylidene fluoride. The isolation membrane can be a single-layer film or a multi-layer composite film, without particular limitation. When the isolation membrane is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0142] [Preparation method]

[0143] Next, the method for preparing the lithium-ion battery in the aforementioned embodiment is introduced.

[0144] The present application also provides a method for preparing a lithium-ion battery. Figure 1 is a schematic flow chart of the preparation method.

[0145] like Figure 1 As shown, the method 100 includes:

[0146] S101, preparing a lithium-philic metal in the negative electrode active material layer of the negative electrode sheet.

[0147] S102, adding metal ions into the electrolyte, wherein the reduction potential of the metal ions is higher than the reduction potential of the lithium ions.

[0148] S103, assembling the negative electrode plate and the electrolyte into a lithium-ion battery.

[0149] In other words, a lithium-philic metal is prepared in the negative electrode active material layer, metal ions are added to the electrolyte, and the negative electrode sheet including the lithium-philic metal and the electrolyte including the metal ions are used to prepare a lithium-ion battery. For example, after the negative electrode sheet including the lithium-philic metal, the positive electrode sheet and the separator are wound to form an electrode assembly, the electrode assembly is placed in a housing, the electrolyte including the metal ions is injected, and then the housing is packaged to obtain a lithium-ion battery.

[0150] It should be understood that in the process of implementing method 100, the lithium-philic metal can be first prepared in the negative electrode active material layer, and then the metal ions are added to the electrolyte; or the metal ions can be first added to the electrolyte, and then the lithium-philic metal is prepared in the negative electrode active material layer; or the lithium-philic metal can be prepared in the negative electrode active material layer and the metal ions can be added to the electrolyte at the same time.

[0151] Optionally, in S101, preparing the lithium-philic metal in the negative electrode active material layer includes: preparing the lithium-philic metal on the surface of the negative electrode active material layer close to the electrolyte.

[0152] Optionally, in S101 , preparing the lithium-philic metal in the negative electrode active material layer includes: preparing the lithium-philic metal by chemical reaction.

[0153] Optionally, the chemical reaction includes atomic layer deposition, liquid phase deposition, solid phase deposition.

[0154] For example, by using atomic layer deposition, the lithium-philic metal can be plated on the surface of the negative electrode active material layer layer by layer in the form of a single atomic film. Atomic layer deposition is advantageous for preparing lithium-philic metals with smaller particle sizes. For another example, by using liquid phase deposition, the negative electrode active material layer can be placed in a solution, and the lithium-philic metal can be prepared at the position where the negative electrode active material layer contacts the solution through a chemical reaction in the solution. For another example, by using solid phase deposition, a precursor can be set in the negative electrode active material layer, and the precursor can be induced to react at high temperature to obtain a lithium-philic metal. Optionally, after liquid phase deposition or solid phase deposition, acid washing can be performed to prepare a lithium-philic metal with smaller particle size.

[0155] Optionally, in S101 , preparing the lithium-philic metal in the negative electrode active material layer includes: preparing the lithium-philic metal by electrochemical reaction.

[0156] Optionally, the electrochemical reaction comprises reducing the metal ions at a reduction potential of the metal ions to obtain the lithium-philic metal.

[0157] Specifically, an inorganic salt including metal ions and anions can be directly added to the electrolyte, and the voltage of the lithium-ion battery is adjusted to the reduction potential of the metal ions, so that the metal ions are reduced to lithium-philic metals on the surface of the negative electrode active material layer.

[0158] It should be understood that the metal ions used for the electrochemical reduction reaction are metal ions corresponding to the lithium-philic metal, and may be the same as or different from the metal ions in the lithium-ion battery electrolyte of the aforementioned embodiment. In other words, in one embodiment, the lithium-philic metal can be directly reduced from the metal ions in the electrolyte.

[0159] Optionally, the SEI film of the negative electrode plate includes at least one of lithium-philic metal fluorides and carbonates.

[0160] The formation process of the SEI film usually occurs at the solid-liquid interface between the negative electrode active material layer and the electrolyte. Therefore, for lithium-ion batteries whose negative electrode active material layer includes a lithium-philic metal, the lithium-philic metal will also participate in the formation of the SEI film, and the SEI film after formation includes the lithium-philic metal. In addition, in the process of preparing the lithium-philic metal by electrochemical reaction, since inorganic salts are added to the electrolyte, some inorganic salts may still remain in the electrolyte after the lithium-philic metal is prepared. This part of the inorganic salt can participate in the formation of the SEI film, so that the SEI film includes at least one of the fluorides and carbonates of the lithium-philic metal.

[0161] Optionally, in S102, adding metal ions to the electrolyte includes: adding an inorganic salt to the electrolyte, the inorganic salt includes metal ions and anions, and the anions include at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonimide anions.

[0162] Optionally, the lithium-philic metal includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

[0163] Optionally, the metal ion includes Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

[0164] Based on similar principles, the lithium-ion battery in the aforementioned embodiment that can be prepared by method 100 has a negative electrode plate including a lithium-philic metal and an electrolyte including metal ions, and can achieve corresponding technical effects, which will not be described in detail here.

[0165] In one embodiment, the negative electrode sheet, the positive electrode sheet and the separator may be formed into an electrode assembly by a winding process or a lamination process.

[0166] In one embodiment, the battery cell may include an outer packaging, which may be used to encapsulate the electrode assembly and the electrolyte.

[0167] In one embodiment, the outer packaging of the battery cell may be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the battery cell 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.

[0168] The present application has no particular restrictions on the shape of the battery cell, which can be cylindrical, square or any other shape. For example, Figure 2 The battery cell 200 is a square structure as an example.

[0169] It should be understood that the battery cell 200 may include the lithium-ion battery in the aforementioned embodiment.

[0170] Figure 3 300 is an example of a battery module. Figure 3 In the battery module 300, the plurality of battery cells 200 may be arranged in sequence along the length direction of the battery module 300. Of course, they may also be arranged in any other manner. The plurality of battery cells 200 may further be fixed by fasteners. The plurality of battery cells 200 may be battery cells 200 of the same chemical system or battery cells 200 of different chemical systems.

[0171] Optionally, in one embodiment, the battery module 300 may further include a housing having an accommodation space, and the plurality of battery cells 200 are accommodated in the accommodation space.

[0172] Optionally, in one embodiment, the battery modules 300 may also be assembled into a battery. The number of battery modules 300 contained in the battery may be one or more, and the specific number may be selected by those skilled in the art according to the application and capacity of the battery.

[0173] Figure 4 and Figure 5 400 is an example of a battery. Figure 3 and Figure 4 The battery 400 may include a battery box and a plurality of battery modules 300 disposed in the battery box. The battery box includes an upper box body 401 and a lower box body 402. The upper box body 401 can cover the lower box body 402 and form a closed space for accommodating the battery modules 300. The plurality of battery modules 300 may be arranged in the battery box in any manner.

[0174] It should be understood that in other embodiments, the battery 400 is also referred to as a battery pack. The battery cells 200 may first form a battery module 300, and the battery 400 may be formed by the battery module 300. Alternatively, the battery 400 may be directly formed by the battery cells 200, omitting the intermediate form of the battery module 300.

[0175] In addition, the present application also provides an electrical device, which includes at least one of the lithium-ion battery in the aforementioned embodiment or the lithium-ion battery prepared by method 100.

[0176] In another embodiment, the power-consuming device includes at least one of the battery cell 200, battery module 300, or battery 400 provided in the present application. The battery cell 200, battery module 300, or battery 400 can be used as a power source for the power-consuming device, or as an energy storage unit for the power-consuming device. The power-consuming device may include mobile devices (such as mobile phones, laptops, etc.), electric vehicles (such as pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc., but is not limited thereto.

[0177] As an electric device, a battery cell 200, a battery module 300, or a battery 400 may be selected according to its usage requirements.

[0178] As an example of an electric device, the electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle, etc. In order to meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or a battery module may be used.

[0179] Another example of a device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is usually required to be thin and light, and a secondary battery may be used as a power source.

[0180] Hereinafter, the embodiments of the present application will be described. The embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If no specific techniques or conditions are indicated in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. If the manufacturer is not indicated in the reagents or instruments used, they are all conventional products that can be obtained commercially.

[0181] [Examples 1-16 and Comparative Examples 1-3]

[0182] Example 1

[0183] (1) Preparation of negative electrode sheet

[0184] The negative electrode active material graphite, the conductive agent acetylene black, the binder styrene butadiene rubber (SBR), and the thickener sodium carboxymethyl cellulose (CMC) are dissolved in the solvent deionized water and mixed evenly to obtain the negative electrode slurry. The negative electrode slurry is then evenly coated on the negative electrode current collector copper foil. After cold pressing and cutting, the negative electrode sheet is obtained. The lithium-philic metal in the negative electrode active material layer is prepared by electrochemical reaction, which will be introduced in detail in the preparation process of lithium-ion batteries.

[0185] (2) Preparation of positive electrode sheet

[0186] The positive electrode active material lithium nickel cobalt manganese oxide, the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are dissolved in N-methylpyrrolidone (NMP) and mixed evenly to obtain the positive electrode slurry. The positive electrode slurry is then evenly coated on the positive electrode current collector aluminum foil. After cold pressing and slitting, the positive electrode sheet is obtained.

[0187] (3) Preparation of electrolyte

[0188] The inorganic salt magnesium nitrate was added to a LiPF6 electrolyte with a concentration of 1 mol / L so that the mass fraction of magnesium nitrate in the electrolyte was 0.8%. At this time, the content of magnesium ions in the electrolyte was 1300 ppm, and electrolyte 1 was obtained.

[0189] The inorganic salt magnesium nitrate is added to a LiPF6 electrolyte with a concentration of 1 mol / L so that the mass fraction of the magnesium nitrate is 1.2%. At this time, the content w2 of magnesium ions in the electrolyte is 2000 ppm, and electrolyte 2 is obtained.

[0190] The content of a substance in the electrolyte can be understood as the mass content of the substance in the electrolyte.

[0191] (4) Preparation of lithium-ion batteries

[0192] The positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet and can separate the positive electrode sheet from the negative electrode sheet; then the stacked components are wound and placed in a shell, and after drying, the electrolyte 1 is injected, and the battery is obtained after packaging.

[0193] The battery was charged at 0.6V (vs Li + / Li), so that the free magnesium ions in electrolyte 1 are reduced to lithium-philic metal (magnesium) on the surface of the negative electrode active material layer. The negative electrode sheet at this time is detected to obtain the content w1 and size d of the lithium-philic metal (magnesium). Then, electrolyte 1 is removed, electrolyte 2 is added, and a lithium-ion battery is obtained after packaging.

[0194] In Example 1, the content of the lithium-philic metal in the negative electrode active material layer of the lithium-ion battery is w1=300 ppm, the size of the lithium-philic metal is d=2 nm, and the content of the metal ions in the electrolyte is w2=2000 ppm.

[0195] Example 2

[0196] Compared with Example 1, in Example 2, w1=100 ppm.

[0197] Example 3

[0198] Compared with Example 1, in Example 3, w1=1000 ppm.

[0199] Example 4

[0200] Compared with Example 1, w1 in Example 4 is 1200 ppm.

[0201] Example 5

[0202] Compared with Example 1, d in Example 6 is 3 nm.

[0203] Example 6

[0204] Compared with Example 1, Example 6 prepares a lithium-philic metal by atomic layer deposition. The specific process is: using bis(cyclopentadienyl)magnesium as a precursor and ozone as a reactant, a precursor pulse of 300s, a nitrogen purge of 120s, an ozone pulse of 40s, and a nitrogen purge of 20s, as one cycle, and a metal magnesium is deposited on the graphite surface after one cycle. Thus, a lithium-philic metal with d=0.3nm is obtained.

[0205] Example 7

[0206] Compared with Example 1, Example 7 prepared the lithium-philic metal by liquid phase deposition. The specific process is: magnesium chloride and graphite are mixed in water, stirred evenly, and then the water is removed by rotary evaporation, and then the obtained sample is reduced at 500°C for 2h in an atmosphere containing argon-hydrogen mixed gas (95% Ar, 5% H2); the loaded sample is then pickled in 1mol / L hydrochloric acid, and after pickling for 12h, it is filtered until the filtrate is neutral. Thus, a lithium-philic metal with d=20nm is obtained.

[0207] Example 8

[0208] Compared with Example 1, in Example 8, w2=500 ppm.

[0209] Example 9

[0210] Compared with Example 1, in Example 9, w2=50000 ppm.

[0211] Example 10

[0212] Compared with Example 1, w2 in Example 10 is 20000 ppm.

[0213] Embodiment 11

[0214] Compared with Example 1, w2 in Example 11 is 400 ppm.

[0215] Example 12

[0216] Compared with Example 1, in the process of preparing the electrolyte in Example 12, the inorganic salt added to the electrolyte 1 is magnesium hexafluorophosphate, and the mass fraction of magnesium hexafluorophosphate in the electrolyte 1 is 1.7%. The inorganic salt added to the electrolyte 2 is magnesium hexafluorophosphate, and the mass fraction of magnesium hexafluorophosphate in the electrolyte 2 is 2.6%. Therefore, w2 in Example 12 is 2000ppm.

[0217] Embodiment 13

[0218] Compared with Example 1, in the process of preparing the electrolyte in Example 13, the inorganic salt added to the electrolyte 1 is magnesium bistrifluoromethanesulfonyl imide, and the mass fraction of magnesium bistrifluoromethanesulfonyl imide in the electrolyte 1 is 3.2%. The inorganic salt added to the electrolyte 2 is magnesium bistrifluoromethanesulfonyl imide, and the mass fraction of magnesium bistrifluoromethanesulfonyl imide in the electrolyte 2 is 4.9%. Therefore, w2 in Example 13 is 2000ppm.

[0219] Embodiment 14

[0220] Compared with Example 1, the lithium-philic metal in Example 14 is tin. Specifically, in the process of preparing the electrolyte, the inorganic salt added to the electrolyte 1 and the electrolyte 2 is tin nitrate, and the mass fraction is 2.0% and 3.1% respectively. In the process of preparing the lithium-ion battery, at 2.0V (vs Li + / Li) under constant voltage discharge conditions, so that the free tin ions in electrolyte 1 are reduced to lithium-philic metal (tin) on the surface of the negative electrode active material layer. Then, electrolyte 1 is removed, electrolyte 2 is added, and a lithium ion battery is obtained after packaging. In Example 14, w1=300ppm, w2=2000ppm, and d=2nm.

[0221] Embodiment 15

[0222] Compared with Example 1, the lithium-philic metal in Example 15 is silver. Specifically, in the process of preparing the electrolyte, the inorganic salt added to the electrolyte 1 and the electrolyte 2 is silver nitrate, and the mass fractions are 0.9% and 1.4%, respectively. In the process of preparing the lithium-ion battery, at 2.0V (vs Li + / Li) is used for constant voltage discharge, so that the free silver ions in electrolyte 1 are reduced to lithium-philic metal (silver) on the surface of the negative electrode active material layer. Then, electrolyte 1 is removed, electrolyte 2 is added, and a lithium ion battery is obtained after packaging. In Example 15, w1=300ppm, w2=2000ppm, and d=2nm.

[0223] Example 16

[0224] Compared with Example 1, the metal ions in Example 16 are silver ions. Specifically, when preparing the electrolyte 2, the inorganic salt added is silver nitrate, with a mass fraction of 1.4%. In Example 16, w2=2000ppm.

[0225] Comparative Example 1

[0226] Compared with Example 1, there is no lithium-philic metal in the negative electrode active material layer of the negative electrode sheet in Comparative Example 1, and there is no metal ion in the electrolyte. Specifically, in the process of preparing the lithium-ion battery, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet and can isolate the positive electrode sheet and the negative electrode sheet; then the stacked components are wound and placed in a shell, and after drying, a LiPF6 electrolyte with a mass fraction of 12.7% is injected, and the lithium-ion battery is obtained after packaging.

[0227] Comparative Example 2

[0228] Compared with Example 1, the negative electrode active material layer of the negative electrode plate in Comparative Example 2 includes a lithium-philic metal but no metal ions in the electrolyte. Specifically, in the process of preparing the lithium-ion battery, after removing the electrolyte 1, a LiPF6 electrolyte with a mass fraction of 12.7% is injected, and the lithium-ion battery is obtained after packaging.

[0229] Comparative Example 3

[0230] Compared with Example 1, the negative electrode active material layer of the negative electrode sheet in Comparative Example 3 does not contain a lithium-philic metal, but the electrolyte includes metal ions. Specifically, in the process of preparing a lithium-ion battery, the positive electrode sheet, the separator, and the negative electrode sheet are stacked in order, so that the separator is between the positive electrode sheet and the negative electrode sheet and can isolate the positive electrode sheet from the negative electrode sheet; then the stacked components are wound and placed in a shell, and after drying, the electrolyte 2 is injected, and the lithium-ion battery is obtained after packaging.

[0231] The product parameters of Examples 1-16 and Comparative Examples 1-3 are shown in Table 1

[0232] Table 1: Product parameters of Examples 1-16 and Comparative Examples 1-3

[0233] In Table 1, "lithium-philic metal" refers to the lithium-philic metal in the negative electrode active material layer; "preparation method" refers to the preparation method of the lithium-philic metal; "w1" refers to the content of the lithium-philic metal in the negative electrode plate; "d" refers to the size of the lithium-philic metal; "inorganic salt" refers to the substance that provides metal ions in the electrolyte; "metal ions" refers to metal ions in the electrolyte; "w2" refers to the content of the lithium-philic metal in the electrolyte.

[0234] The lithium ion batteries in Examples 1-16 and Comparative Examples 1-3 were subjected to performance tests, and the obtained product performance data are shown in Table 2.

[0235] Table 2 Product performance data of Examples 1-16 and Comparative Examples 1-3

[0236] According to the comparative analysis of Examples 1-16 and Comparative Examples 1-3, by introducing lithium-philic metals into the negative electrode active material layer and introducing metal ions into the electrolyte, the growth of lithium dendrites can be continuously suppressed during the long cycle of the battery, effectively improving the cycle performance and service life of the lithium-ion battery.

[0237] For the DCR of lithium-ion batteries, it can be seen that the DCR of the lithium-ion batteries of Examples 1-16 is only slightly greater than the DCR of Comparative Examples 1-3, but the cycle performance of the lithium-ion batteries in the examples are significantly higher than that of the comparative examples. This shows that by introducing lithium-philic metals and metal ions into lithium-ion batteries, the DCR of lithium-ion batteries is affected to a certain extent, but overall, it helps to significantly improve the cycle performance of lithium-ion batteries. According to the comparative analysis of Examples 1-4, as the content w1 of the lithium-philic metal in the negative electrode sheet increases, the DCR of the lithium-ion battery increases. The content w1 of the lithium-philic metal in the negative electrode sheet of Example 4 is 1200ppm, which exceeds the range of 100ppm-1000ppm, and the DCR of the lithium-ion battery is significantly increased. Therefore, it is shown that by controlling w1 within a suitable range, the impedance of the lithium-ion battery can be improved while the cycle performance of the lithium-ion battery is not significantly increased.

[0238] As for the self-discharge of lithium-ion batteries, it can be seen that the self-discharge of the lithium-ion batteries of Examples 1-16 is only slightly greater than the self-discharge performance of the lithium-ion batteries of Comparative Examples 1-3, but the cycle performance of the lithium-ion batteries in the examples is significantly higher than that of the comparative examples. It is shown that the introduction of lithium-philic metals and metal ions into lithium-ion batteries has a certain degree of influence on the self-discharge of lithium-ion batteries, but overall, it helps to significantly improve the cycle performance of lithium-ion batteries. According to the comparative analysis of Example 1 and Example 5-7, the lithium-philic metal in the negative electrode active material layer can be prepared by different methods such as electrochemical reduction, atomic layer deposition, and liquid phase deposition. In addition, the size d of the lithium-philic metal in Example 1 and Example 5-6 is relatively small (0nm<d≤3nm), and the self-discharge of the lithium-ion battery is relatively small. In Example 7, the size d of the lithium-philic metal reaches 20nm, and the self-discharge of the lithium-ion battery is greater than that of Example 5-6. If the self-discharge of the lithium-ion battery is further increased, it is not conducive to the improvement of its cycle performance. Therefore, it is shown that by controlling the size of the lithium-philic metal within a suitable range, the self-discharge of the lithium-ion battery can be improved while the cycle performance of the lithium-ion battery is not significantly increased.

[0239] According to the comparative analysis of Example 1 and Examples 8-11, it can be seen that the content w2 of metal ions in the electrolyte in the lithium ion battery of Example 11 is 400ppm, which is not within the range of 500ppm-50000ppm. Because the content of metal ions is too small, the inhibitory effect on lithium dendrites is limited, and the lithium ion battery fails after 800 cycles. The lithium ion batteries in other embodiments can circulate 1500 cycles without failure. Thus, it is shown that by controlling the content of metal ions within a suitable range, a continuous inhibitory effect can be produced on lithium dendrites, thereby helping to improve the cycle performance of lithium ion batteries. It can also be seen from Examples 8-10 that as the content of metal ions in the electrolyte increases, the impedance of the lithium ion battery increases. Thus, it is shown that by controlling the content of metal ions within a suitable range, the impedance of the lithium ion battery can be made not to increase significantly.

[0240] Examples 12-13 illustrate that the lithiophilic metal can be provided by salts other than magnesium nitrate.

[0241] Examples 14-15 illustrate that the lithium-philic metal may also be tin or silver; the metal ion may also be tin ion or silver ion.

[0242] In Example 16, the lithium-philic metal is magnesium and the metal ion is silver ion, which illustrates that the elements of the lithium-philic metal and the metal ion can be the same or different.

[0243] [Examples 17-23 and Comparative Example 4]

[0244] Embodiment 17

[0245] The lithium ion battery in Example 17 is a lithium ion battery after 1500 cycles of the lithium ion battery in Example 1. The lithium ion battery is disassembled to detect the content w3 of magnesium metal in the negative electrode plate of the lithium ion battery and the content w4 of metal magnesium ions in the electrolyte. In Example 17, w3=800ppm, w4=200ppm.

[0246] Embodiment 18

[0247] The lithium ion battery in Example 18 is a lithium ion battery after 10 cycles of the lithium ion battery in Example 2. In Example 18, w3=100 ppm, w4=2000 ppm.

[0248] Embodiment 19

[0249] The lithium ion battery in Example 19 is a lithium ion battery after 1500 cycles of the lithium ion battery in Example 2. In Example 19, w3=600ppm, w4=900ppm.

[0250] Embodiment 20

[0251] The lithium ion battery in Example 20 is a lithium ion battery after 1500 cycles of the lithium ion battery in Example 4. In Example 20, w3=3000ppm, w4=100ppm.

[0252] Embodiment 21

[0253] The lithium ion battery in Example 21 is a lithium ion battery after 10 cycles of the lithium ion battery in Example 8. In Example 21, w3=300ppm, w4=500ppm.

[0254] Embodiment 22

[0255] The lithium ion battery in Example 22 is a lithium ion battery after 1500 cycles of the lithium ion battery in Example 8. In Example 22, w3=400ppm, w4=100ppm.

[0256] Embodiment 23

[0257] The lithium ion battery in Example 23 is a lithium ion battery after 1000 cycles of the lithium ion battery in Example 9. In Example 23, w3=800ppm, w4=48000ppm.

[0258] Comparative Example 4

[0259] Comparative Example 4 is a lithium ion battery of Comparative Example 1 after 100 cycles.

[0260] Comparative Example 5

[0261] Comparative Example 5 is a lithium ion battery of Comparative Example 2 after 500 cycles.

[0262] Comparative Example 6

[0263] Comparative Example 6 is a lithium-ion battery of Comparative Example 3 after 600 cycles.

[0264] The product parameters and performance parameters of Examples 17-23 and Comparative Examples 4-6 are shown in Table 3

[0265] Table 3: Product parameters and performance parameters of Examples 17-23 and Comparative Examples 4-6 w1(ppm) w2(ppm) w3(ppm) w4(ppm) Number of cycles Failure circle number Embodiment 17 300 2000 800 200 1500 ＞1500 Embodiment 18 100 2000 100 2000 10 ＞1500 Embodiment 19 100 2000 600 900 1500 ＞1500 Embodiment 20 1200 2000 3000 100 1500 ＞1500 Embodiment 21 300 500 300 500 10 ＞1500 Embodiment 22 300 500 400 100 1500 ＞1500 Embodiment 23 300 50000 800 48000 1000 ＞1500 Comparative Example 4 / / / / 100 100 Comparative Example 5 300 / 200 / 500 500 Comparative Example 6 / 2000 700 100 600 600

[0266] In Table 2, "w1" indicates the content of lithium-loving metal in the negative electrode sheet of the lithium-ion battery before cycling; "w2" indicates the content of lithium-loving metal in the electrolyte of the lithium-ion battery before cycling; "w3" indicates the content of lithium-loving metal in the negative electrode sheet of the lithium-ion battery after cycling; "w4" indicates the content of metal ions in the electrolyte of the lithium-ion battery after cycling. "Number of failure cycles" indicates the number of battery cycle failure cycles.

[0267] According to the data in Table 3, the content of lithium-philic metal in the lithium-ion battery after cycling is related to the content of lithium-philic metal before cycling. The content of metal ions in the lithium-ion battery after cycling is related to the content of metal ions before cycling.

[0268] According to the comparative analysis of Example 17 and Comparative Examples 4-6, it can be explained that introducing lithium-philic metals into the negative electrode active material layer and introducing metal ions into the electrolyte can continuously suppress lithium dendrites in the long cycle of the lithium-ion battery, thereby effectively improving the cycle performance and service life of the lithium-ion battery.

[0269] According to the comparative analysis of Examples 18-19 and 21-22, it can be reasonably inferred that in the long cycle process of lithium-ion batteries, when the lithium-ion battery just begins to precipitate lithium (when the number of cycles is small), it first forms a lithium-metal alloy with the lithium-philic metal in the negative electrode active material layer. Since the lithium-metal alloy is still in the negative electrode active material layer, and the metal ions in the electrolyte are not consumed at this time. Therefore, in Examples 18 and 21, the lithium-philic metal content before and after the cycle is consistent with the metal ion content. With the further cycle of the battery, lithium precipitation further occurs, and after the lithium dendrites grow and pierce the SEI film, the metal ions in the electrolyte begin to be consumed, and lithium-metal alloys are further formed. Therefore, in Examples 19 and 22, in the lithium-philic metal content of the lithium-ion battery after the cycle, the metal ion content in the electrolyte is significantly increased, while the metal ion content in the electrolyte is significantly decreased.

[0270] The following is a brief introduction to the test methods of the physical and chemical parameters and performance parameters involved in the embodiments of the present application. It should be understood that the following test methods are only examples, and other test methods known in the art may also be used for testing.

[0271] 1. Test method for reduction potential of metal ions

[0272] According to the Nernst equation, the reduction potential of metal ions to lithium at different concentrations relative to 1 mol / L concentration is calculated, and the metal ions can be reduced by selecting a potential to lithium less than this potential.

[0273] 2. Test method of content

[0274] Take part of the sample to be tested, such as the negative electrode and electrolyte; and directly measure the content of the target element in the sample through ICP (Inductively coupled plasma) testing.

[0275] 3. Size test method

[0276] Take part of the sample to be tested, such as the negative electrode, and test it through TEM (Transmission electron microscope) or AC-TEM (Spherical Aberration corrected transmission electron microscope) to obtain a microscopic photo of the sample, thereby obtaining the size of the sample.

[0277] 4. Test method for self-discharge of lithium-ion batteries

[0278] The battery is charged to 3.75V (nickel cobalt manganese oxide positive electrode) at a constant current of 0.33C, and then charged to 0.05C at a constant voltage of 3.75V. After the battery cell is left at room temperature for 12 hours, the voltage V0 of the battery is tested at this time. After leaving it for another 48 hours, the voltage V1 is tested, and the self-discharge is (V1-V0) / 48.

[0279] 5. Test method for DCR of lithium-ion batteries

[0280] The prepared lithium-ion battery was first discharged at 25°C with a current of 0.33C to a voltage of 2.5V. After standing for 30 minutes, it was charged at a current of 0.33C to a voltage of 4.3V, and then charged at a constant voltage at a voltage of 4.3V until the current was less than 0.05C. After standing for 30 minutes, it was discharged at a current of 0.33C to a voltage of 2.5V. At this time, the capacity of the battery C0 was obtained. Then the battery was charged at a current of 0.33C to a voltage of 4.3V, and then charged at a constant voltage at a voltage of 4.3V until the current was less than 0.05C. After standing for 30 minutes, it was discharged at a current of 0.33C to a capacity of 0.5C0, so that the SOC of the lithium-ion battery was 50%. At this time, the voltage of the battery was recorded as V1. Then it was discharged at a current of 4C for 30s. At this time, the voltage of the battery was recorded as V2. According to the formula: (V1-V2) / (4C×1000), the DCR (unit mΩ) of the battery was obtained.

[0281] 6. Test method for the number of cycles of failure of lithium-ion batteries

[0282] Charge the lithium-ion battery at 2C current to 4.3V, then charge at 4.3V at constant voltage until the current is less than 0.05C, leave it for 30 minutes, and then discharge it at 1C current to 2.5V. Repeat the above steps and record the number of cycles when the capacity of the lithium-ion battery decays to 80%.

[0283] Although the present application has been described with reference to preferred embodiments, various modifications may be made thereto and parts thereof may be replaced with equivalents without departing from the scope of the present application. In particular, the various technical features mentioned in the various embodiments may be combined in any manner as long as there are no structural conflicts. The present application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A lithium ion battery, characterized in that: The lithium-ion battery comprises: A negative electrode plate, wherein the negative electrode active material layer of the negative electrode plate includes a lithium-philic metal; An electrolyte comprises metal ions, wherein the reduction potential of the metal ions is higher than the reduction potential of lithium ions.

2. The lithium-ion battery according to claim 1, characterized in that The lithium-philic metal is located on the surface of the negative electrode active material layer close to the electrolyte.

3. The lithium ion battery according to claim 1 or 2, characterized in that: The lithium-philic metal includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

4. The lithium ion battery according to any one of claims 1 to 3, characterized in that: The content w1 of the lithium-philic metal in the negative electrode sheet satisfies: 100ppm≤w1≤1000ppm.

5. The lithium ion battery according to any one of claims 1 to 4, characterized in that: The lithium-philic metal includes single atoms and / or particles, and the size d of the particles satisfies: 0<d≤3nm.

6. The lithium ion battery according to any one of claims 1 to 5, characterized in that: The metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

7. The lithium ion battery according to any one of claims 1 to 6, characterized in that: The content w2 of the metal ions in the electrolyte satisfies: 500ppm≤w2≤50000ppm; optionally, 2000ppm≤w2≤20000ppm.

8. The lithium ion battery according to any one of claims 1 to 7, characterized in that: The electrolyte includes an inorganic salt, and the inorganic salt includes the metal ion and an anion; The anions include at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonyl imide anions.

9. The lithium ion battery according to any one of claims 1 to 8, characterized in that: The lithiophilic metal is obtained by chemical reaction.

10. The lithium ion battery according to claim 9, characterized in that: The chemical reaction includes atomic layer deposition, liquid phase deposition, and solid phase deposition.

11. The lithium ion battery according to any one of claims 1 to 8, characterized in that: The SEI film of the negative electrode plate includes at least one of the fluorides and carbonates of the lithium-philic metal.

12. The lithium ion battery according to claim 11, characterized in that: The lithium-philic metal is obtained by an electrochemical reaction.

13. A lithium ion battery, characterized in that: The lithium-ion battery comprises: A negative electrode plate, wherein the negative electrode active material layer of the negative electrode plate comprises a lithium-metal alloy; An electrolyte comprises metal ions, wherein the reduction potential of the metal ions is higher than the reduction potential of lithium ions.

14. The lithium ion battery according to claim 13, characterized in that: The negative electrode active material layer includes a lithium-philic metal, and the lithium-metal alloy includes an alloy formed of lithium and the lithium-philic metal.

15. The lithium ion battery according to claim 13 or 14, characterized in that: The lithium-metal alloy also includes an alloy formed by lithium and a metal obtained by reducing the metal ions.

16. The lithium ion battery according to any one of claims 13 to 15, characterized in that: The lithium-metal alloy is located on a surface of the negative electrode active material layer close to the electrolyte.

17. The lithium ion battery according to any one of claims 14 to 16, characterized in that: The content w3 of the lithium-philic metal in the negative electrode sheet satisfies: 100ppm≤w3≤3000ppm.

18. The lithium ion battery according to any one of claims 13 to 17, characterized in that: The metal in the lithium-metal alloy includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

19. The lithium ion battery according to any one of claims 13 to 18, characterized in that: The metal ions include Mg 2+ Sn 4+ 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

20. The lithium ion battery according to any one of claims 13 to 19, characterized in that: The content w4 of the metal ions in the electrolyte satisfies: 100ppm≤w4≤48000ppm; optionally, 300ppm≤w4≤19000ppm.

21. A method for preparing a lithium ion battery, characterized in that: The method comprises: preparing a lithium-philic metal in a negative electrode active material layer of a negative electrode sheet; Adding metal ions into the electrolyte, wherein the reduction potential of the metal ions is higher than the reduction potential of the lithium ions; The negative electrode plate and the electrolyte are assembled into a lithium-ion battery.

22. The method according to claim 21, characterized in that The step of preparing a lithium-philic metal in the negative electrode active material layer of the negative electrode plate comprises: The lithium-philic metal is prepared on the surface of the negative electrode active material layer close to the electrolyte.

23. The method according to claim 21 or 22, characterized in that The step of preparing a lithium-philic metal in the negative electrode active material layer of the negative electrode plate comprises: The lithium-philic metal is prepared by a chemical reaction.

24. The method according to claim 23, characterized in that The chemical reaction includes atomic layer deposition, liquid phase deposition, and solid phase deposition.

25. The method according to claim 21 or 22, characterized in that The step of preparing a lithium-philic metal in the negative electrode active material layer of the negative electrode plate comprises: The lithium-philic metal is prepared by an electrochemical reaction.

26. The method according to claim 25, characterized in that The electrochemical reaction includes: The metal ion is reduced at the reduction potential of the metal ion to obtain the lithiophilic metal.

27. The method according to claim 26, characterized in that The SEI film of the negative electrode plate includes at least one of the fluorides and carbonates of the lithium-philic metal.

28. The method according to any one of claims 21 to 27, characterized in that The step of adding metal ions to the electrolyte comprises: An inorganic salt is added to the electrolyte, wherein the inorganic salt includes the metal ion and an anion, and the anion includes at least one of acetate, nitrate, hexafluorophosphate, perchlorate, and bistrifluoromethanesulfonyl imide anions.

29. The method according to any one of claims 21 to 28, characterized in that The lithium-philic metal includes at least one of Mg, Sn, Ag, Al, In, Zn, Ca, Sr, Ba, Sc, Y, Rh, Ir, Pd, Pt, Au, Cd, Ga, Ge, Pb, Sb, and Bi.

30. The method according to any one of claims 21 to 29, characterized in that The metal ions include Mg 2+ Sn 4 + 、Ag + 、Al 3+ 、In 3+ 、Zn 2+ , Ca 2+ , Sr 2+ , Ba 2+ Sc + , Y 3+ , Rh 3+ , Ir 3+ , Pd 3+ , Pt 3+ 、Au 2+ 、Cd 2+ , Ga 3+ ,Ge 4+ , Pb 4+ , Sb 3+ 、Bi 3+ At least one of .

31. An electrical device, characterized in that: The electrical device comprises at least one of the lithium ion battery according to any one of claims 1 to 12, the lithium ion battery according to any one of claims 13 to 20, and the lithium ion battery prepared by the method according to any one of claims 21 to 30.

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