Lithium ion battery and electric device

Abstract

The invention provides a lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, the positive electrode comprises a positive electrode active material layer and a positive electrode current collector, the surface of the positive electrode current collector is provided with a safety coating, the positive electrode active material layer is arranged on the surface of the safety coating, and the surface of the diaphragm facing the positive electrode is provided with an oxide solid electrolyte coating; the electrolyte comprises a first additive and a second additive, the first additive comprises an acrylate monomer, and the second additive comprises a cross-linking agent; the lithium ion battery meets the following conditions: (H + X) / P is more than or equal to 0.72 and less than or equal to 8; 0.5 < = (A + B) / (H + X) < = 8.89; 0.16 < = H / X < = 6.43; 0.5 < = A / B < = 12; according to the lithium ion battery provided by the invention, through multi-component regulation and control, the safety and the high and low temperature performance of the lithium ion battery are remarkably improved, and further, when the lithium ion battery meets the relation limitation at the same time, the interface impedance can be well reduced, and multi-component parameters are coordinated; and synchronous optimization of thermal safety, low-temperature discharge capacity and high-temperature cycle life of the battery is realized.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a lithium-ion battery and an electrical device thereof. Background Technology

[0002] Lithium-ion batteries are widely used in consumer electronics and electric vehicles due to their core advantages such as high energy density, low self-discharge rate and long cycle life. However, the safety of lithium-ion batteries has always been a key factor restricting their further development. Traditional lithium-ion batteries have the risk of thermal runaway under conditions such as thermal abuse and overcharging.

[0003] To improve safety, a safety coating is usually applied to the positive electrode current collector to provide heat insulation and prevent internal short circuits. Meanwhile, applying an oxide solid electrolyte coating to the separator surface is an effective way to improve ion transport performance. However, while the introduction of the safety coating improves thermal safety, it may also increase interfacial impedance and have a certain negative impact on the low-temperature performance of the battery. Summary of the Invention

[0004] To address the issues of low thermal shock safety and inability to balance high and low temperature performance in traditional lithium-ion batteries, a lithium-ion battery and power device are provided.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: On one hand, the present invention provides a lithium-ion battery, including a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode active material layer and a positive electrode current collector. A safety coating is disposed on the surface of the positive electrode current collector. The positive electrode active material layer is disposed on the surface of the safety coating. An oxide solid electrolyte coating is disposed on the surface of the separator facing the positive electrode. The electrolyte includes a first additive and a second additive, wherein the first additive includes an acrylate monomer and the second additive includes a crosslinking agent. The lithium-ion battery meets the following conditions: 0.72≤(H+X) / P≤8; 0.5≤(A+B) / (H+X)≤8.89; 0.16≤H / X≤6.43; 0.5 ≤ A / B ≤ 12; Where H is the thickness of the safety coating, in μm; X represents the thickness of the oxide solid electrolyte coating on the membrane surface, in μm; P is the liquid retention coefficient of the lithium-ion battery, with units of g / Ah; A% represents the mass percentage of the first additive in the electrolyte; B% represents the mass percentage of the second additive in the electrolyte.

[0006] Optionally, the lithium-ion battery satisfies the following conditions: 1≤(H+X) / P≤4.67.

[0007] Optionally, the lithium-ion battery satisfies the following conditions: 0.87≤(A+B) / (H+X)≤5.67.

[0008] Optionally, the lithium-ion battery satisfies the following conditions: 0.4≤H / X≤5.

[0009] Optionally, the first additive and the second additive satisfy the following conditions: 1≤A / B≤10.

[0010] Optionally, the first additive comprises one or more of butyl acrylate, butyl methacrylate, methyl acrylate, methyl methacrylate, pentafluoropropyl acrylate, trifluoroethyl acrylate, and trifluoroethyl methacrylate; and / or, The second additive includes one or more of pentaerythritol tetraacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ethoxylated trimethylolpropane triacrylate, and polyethylene glycol diacrylate.

[0011] Optionally, the thickness H of the safety coating is 0.5μm≤H≤5μm.

[0012] Optionally, the thickness X of the oxide solid electrolyte coating is 0.5μm≤X≤5μm.

[0013] Optionally, the liquid retention coefficient P of the lithium-ion battery is 0.8 g / Ah to 2.5 g / Ah.

[0014] Optionally, based on the total mass of the electrolyte as 100%, the mass percentage of the first additive is 1% to 15%; Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.5% to 5%.

[0015] Optionally, the raw materials for the safety coating include one or more of lithium iron phosphate and ceramics.

[0016] Optionally, the oxide solid electrolyte coating includes an oxide solid electrolyte, which includes one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconate, lithium aluminum germanium phosphate, and lithium lanthanum titanate.

[0017] Optionally, the positive electrode active material layer includes a positive electrode active material, which includes a transition metal lithium oxide. The chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; Wherein, M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr; The negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one of graphite negative electrode, silicon-carbon composite negative electrode or lithium metal negative electrode.

[0018] On the other hand, the present invention provides an electrical device including the aforementioned lithium-ion battery.

[0019] The beneficial effects provided by this application are as follows: The lithium-ion battery provided in this application includes a positive electrode comprising a positive electrode active material layer and a positive electrode current collector. A safety coating is disposed on the surface of the positive electrode current collector, and the positive electrode active material layer is disposed on the surface of the safety coating. An oxide solid electrolyte coating is disposed on the surface of the separator facing the positive electrode. The electrolyte includes a first additive and a second additive. The first additive includes acrylate monomers, and the second additive includes a crosslinking agent. The safety coating provides physical insulation and protection against internal short circuits. The oxide solid electrolyte coating of the separator constructs a fast ion transport channel. The two additives synergistically improve the safety performance and ion transport of the lithium-ion battery. The first additive, acrylate monomers, can polymerize on the electrode surface to form an elastic polymer interface film, inhibiting electrolyte decomposition and transition metal dissolution. The second additive, crosslinking agent, crosslinks with the monomers to form a three-dimensional network structure, enhancing the mechanical strength and thermal stability of the interface film. The two additives synergistically optimize the electrode interface characteristics, achieving safety protection and ion transport efficiency. Furthermore, through previous verification, this application found that when the thickness H of the safety coating, the thickness X of the oxide solid electrolyte coating on the separator surface, the liquid retention coefficient P of the lithium-ion battery, the mass percentage A% of the first additive, and the mass percentage B of the second additive are controlled, and the following conditions are met simultaneously, the problem of increased interface impedance that may be introduced by the safety coating can be effectively balanced. Thus, the high safety, long cycle life, and wide temperature range performance of the battery can be synergistically optimized from the perspectives of interface stability, ion transport, and thermal safety. Detailed Implementation

[0020] To make the technical problems solved, the technical solutions, and the beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0021] This invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode active material layer and a positive electrode current collector. A safety coating is disposed on the surface of the positive electrode current collector. The positive electrode active material layer is disposed on the surface of the safety coating. An oxide solid electrolyte coating is disposed on the surface of the separator facing the positive electrode. The electrolyte includes a first additive and a second additive, wherein the first additive includes an acrylate monomer and the second additive includes a crosslinking agent. The lithium-ion battery meets the following conditions: 0.72≤(H+X) / P≤8; 0.5≤(A+B) / (H+X)≤8.89; 0.16≤H / X≤6.43; 0.5 ≤ A / B ≤ 12; Where H is the thickness of the safety coating, in μm; X represents the thickness of the oxide solid electrolyte coating on the membrane surface, in μm; P is the liquid retention coefficient of the lithium-ion battery, with units of g / Ah; A% represents the mass percentage of the first additive in the electrolyte; B% represents the mass percentage of the second additive in the electrolyte.

[0022] It should be noted that the core functional group of the first additive (acrylate monomer) is the acrylate group, which has high reactivity and can undergo polymerization under battery operating conditions. The second additive (crosslinking agent) contains multiple polymerizable functional groups and can form a crosslinking network with the acrylate monomer. When the two additives work synergistically, the positive electrode interface is stabilized: the acrylate monomer polymerizes on the positive electrode surface to form a protective film, and the crosslinking agent reacts with the monomer to form a more stable and dense composite interface film. This synergistically suppresses side reactions and transition metal dissolution at the positive electrode / electrolyte interface during high-temperature cycling, significantly improving high-temperature cycling performance. The polymer network formed by the crosslinking agent can effectively suppress dendrite growth and improve the mechanical strength of the interface film. Together, they work to form a highly stable and mechanically strong SEI film on the negative electrode.

[0023] Furthermore, the polymer interfacial film formed by the first and second additives exhibits good thermal stability, and the cross-linked network structure further enhances the thermomechanical properties of the interfacial film. Combined with the physicochemical protective effects of the safety coating and the oxide solid electrolyte coating, these two additives synergistically enhance the battery's safety under thermal abuse conditions.

[0024] The safety coating provides physical isolation and thermal stability, preventing internal short circuits and heat propagation, and greatly improving thermal safety. The oxide solid electrolyte coating on the membrane surface provides additional ion transport channels and improves ion conductivity. However, the increased thickness of the safety coating increases interfacial impedance, which negatively impacts high and low temperature performance. Therefore, it is necessary to verify and control the thickness of the safety coating (H), the oxide solid electrolyte coating on the membrane surface (X), the liquid retention coefficient (P), and the ratio of two complementary additives (A, B) to achieve a balance between high battery safety, long lifespan, and wide temperature range performance.

[0025] Specifically, the lithium-ion battery provided in this application includes a positive electrode comprising a positive electrode active material layer and a positive electrode current collector. A safety coating is disposed on the surface of the positive electrode current collector, and the positive electrode active material layer is disposed on the surface of the safety coating. An oxide solid electrolyte coating is disposed on the surface of the separator facing the positive electrode. The electrolyte includes a first additive and a second additive. The first additive includes acrylate monomers, and the second additive includes a crosslinking agent. The safety coating provides physical insulation and protection against internal short circuits. The oxide solid electrolyte coating of the separator constructs a fast ion transport channel. The two additives synergistically improve the safety performance and ion transport of the lithium-ion battery. The first additive, acrylate monomers, can polymerize on the electrode surface to form an elastic polymer interface film, inhibiting electrolyte decomposition and transition metal dissolution. The second additive, crosslinking agent, crosslinks with the monomers to form a three-dimensional network structure, enhancing the mechanical strength and thermal stability of the interface film. The two additives synergistically optimize the electrode interface characteristics, achieving safety protection and ion transport efficiency. Furthermore, previous verification in this application revealed that if (H+X) / P < 0.72, the solid-state ion conduction pathway is insufficient, the electrolyte is relatively excessive, and the excessive amount of combustible material during thermal shock significantly increases the risk of thermal runaway. Conversely, when (H+X) / P > 8, the solid-solid interface impedance is too high, the electrolyte wetting is insufficient, ion transport is hindered at low temperatures, and capacity decays rapidly. When (A+B) / (H+X) < 0.5, the additive cannot cover the newly added interface of the oxide solid electrolyte, and the electrolyte continues to degrade during high-temperature cycling. In the decomposition process, when (A+B) / (H+X) > 8.89, excessive additive products hinder lithium-ion migration, affecting the overall performance of the lithium-ion battery; when H / X < 0.16, the safety coating is too thin and cannot effectively provide physical protection, resulting in decreased thermal safety; when H / X > 6.43, the safety coating is too thick and may increase interfacial impedance, affecting battery kinetic performance; when A / B < 0.5, insufficient cross-linking leads to a decrease in the mechanical strength of the interfacial film; when A / B > 12, excessive cross-linking embrittles the interfacial film, affecting ion transport. That is, by controlling the thickness H of the safety coating, the thickness X of the oxide solid electrolyte coating on the separator surface, the liquid retention coefficient P of the lithium-ion battery, the mass percentage A% of the first additive, and the mass percentage B of the second additive, while simultaneously satisfying 0.72≤(H+X) / P≤8, 0.5≤(A+B) / (H+X)≤8.89, 0.16≤H / X≤6.43, and 0.5≤A / B≤12, the problem of increased interface impedance that may be introduced by the safety coating can be effectively balanced. Thus, from the aspects of interface stability, ion transport, and thermal safety, the synergistic optimization of high battery safety, long cycle life, and wide temperature range performance can be achieved.

[0026] In some embodiments, the lithium-ion battery satisfies the following conditions: 1≤(H+X) / P≤4.67.

[0027] Specifically, when a lithium-ion battery satisfies 1≤(H+X) / P≤4.67, this parameter relationship is further improved by matching the total coating thickness (the sum of the safety coating thickness H and the oxide solid electrolyte coating thickness X) with the electrolyte retention capacity (in terms of the electrolyte retention coefficient P). The measurement achieves further performance optimization. Compared to the basic range of 0.72≤(H+X) / P≤8, this preferred range can better balance ion transport and electrolyte wetting effect. That is, when the ratio of (H+X) / P is between 1 and 4.67, it ensures that the heat insulation effect of the safety coating and the ion transport performance of the oxide solid electrolyte coating can be fully coordinated, so that the total coating thickness and electrolyte retention capacity are reasonably matched. This matching can not only effectively maintain the thermal stability of the battery, but also improve the ion transport efficiency and low temperature performance without significantly increasing the interface impedance. At the same time, combined with the synergistic effect of the first and second additives contained in the electrolyte, a stable solid electrolyte interface (SEI) film is formed, further optimizing the stability of the electrolyte and electrode interface, thereby maintaining the excellent performance of the battery in a wider temperature range and effectively reducing the risk of internal short circuit.

[0028] In some embodiments, the lithium-ion battery satisfies the following conditions: 0.87≤(A+B) / (H+X)≤5.67.

[0029] Specifically, when the lithium-ion battery further satisfies 0.87≤(A+B) / (H+X)≤5.67, it effectively avoids the problems of insufficient additive function or excessive coating impedance due to too low a ratio, and excessive additives or insufficient coating safety protection due to too high a ratio. Further precise ratio control enables the additives and coatings inside the battery to achieve a better synergistic balance, thereby significantly improving the overall performance and safety of the lithium-ion battery. Without sacrificing thermal safety, it optimizes ion transport efficiency and electrode interface stability, effectively solves the problem of battery performance or safety fluctuations, and ensures the stability and reliability of the battery in long-term use.

[0030] In some embodiments, the lithium-ion battery satisfies the following conditions: 0.4≤H / X≤5.

[0031] Specifically, the optimized coating structure (safety coating, separator surface oxide solid electrolyte coating) is combined with the first additive containing acrylate monomers and the second additive containing crosslinking agent in the electrolyte, which further stabilizes the electrode / electrolyte interface, which is conducive to the formation of a more uniform and dense solid electrolyte interface film and optimizes the overall performance of the battery.

[0032] In some embodiments, the first additive and the second additive satisfy the following conditions: 1≤A / B≤10.

[0033] Specifically, by further limiting the mass percentage ratio A / B of the first additive and the second additive to the range of 1 to 10, the relative amounts of acrylate monomers and crosslinking agents in the electrolyte are kept in balance. This helps to fully promote the polymerization reaction in the electrolyte, form a more uniform and dense polymer network, stabilize the interface between the positive electrode, negative electrode and electrolyte, reduce the occurrence of side reactions, and improve the transport efficiency of lithium ions in the electrolyte.

[0034] In some embodiments, the first additive comprises one or more of butyl acrylate, butyl methacrylate, methyl acrylate, methyl methacrylate, pentafluoropropyl acrylate, trifluoroethyl acrylate, and trifluoroethyl methacrylate; and / or, The second additive includes one or more of pentaerythritol tetraacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ethoxylated trimethylolpropane triacrylate, and polyethylene glycol diacrylate.

[0035] Specifically, when the first additive and the second additive are selected from any one or more of the above-mentioned compounds, they can effectively exert their effects on the positive electrode.

[0036] In some embodiments, the thickness H of the safety coating is 0.5 μm ≤ H ≤ 5 μm.

[0037] The lithium-ion battery of this application features a safety coating on the surface of its positive electrode current collector. This coating provides thermal insulation during battery operation and effectively prevents internal short circuits between the current collector and the positive electrode active material layer under extreme conditions. However, the introduction of the safety coating inevitably increases the ion transport impedance at the positive electrode interface. To fully utilize the safety protection function of the safety coating while minimizing its adverse effects on battery performance, especially low-temperature performance, this application limits the thickness H of the safety coating to a specific range of 0.5 μm to 5 μm. When the thickness H is within this range, the coating ensures sufficient physical strength and thermal insulation to effectively address safety risks such as thermal abuse. At the same time, its thickness is not excessive, thus avoiding a significant increase in ion transport path and interface impedance caused by an excessively thick coating. This precise thickness control optimizes the transport resistance of lithium ions at the interface between the positive electrode active material layer and the safety coating, as well as within the safety coating itself. This maintains good power performance and low-temperature performance while ensuring high battery safety.

[0038] Specifically, the thickness H of the safety coating can be 0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm.

[0039] In some embodiments, the thickness X of the oxide solid electrolyte coating is 0.5 μm ≤ X ≤ 5 μm.

[0040] The thickness X of the oxide solid electrolyte coating refers to the vertical dimension of the oxide solid electrolyte coating disposed on the surface of the separator. This thickness affects the internal ion transport efficiency and interface impedance of the lithium-ion battery. Specifically, controlling the thickness X of the oxide solid electrolyte coating on the separator surface within the range of 0.5 μm to 5 μm effectively solves the performance problems caused by improper coating thickness. This thickness range allows the oxide solid electrolyte coating to provide sufficient ion transport channels, significantly improving the migration rate of lithium ions inside the battery, thereby improving the battery's rate performance and low-temperature performance. Simultaneously, this thickness avoids a sharp increase in interfacial impedance caused by excessive coating thickness, ensuring that the battery has low internal resistance and high energy efficiency during operation. Combined with a safety coating on the positive electrode current collector and specific additives in the electrolyte, this optimized oxide solid electrolyte coating thickness not only improves the overall ionic conductivity of the battery but also further enhances the battery's cycle stability and safety. Specifically, the thickness H of the oxide solid electrolyte coating can be 0.5μm, 1μm, 2μm, 3μm, 4μm or 5μm.

[0041] In some embodiments, the liquid retention coefficient P of the lithium-ion battery is 0.8 g / Ah to 2.5 g / Ah.

[0042] Specifically, this application ensures a moderate amount of electrolyte within the battery by limiting the electrolyte retention coefficient P of the lithium-ion battery to the range of 0.8 g / Ah to 2.5 g / Ah. When the electrolyte retention coefficient P is too low (below 0.8 g / Ah), the amount of electrolyte is insufficient to fully wet the positive electrode active material layer, safety coating, separator, and oxide solid electrolyte coating on the separator surface, resulting in a significant increase in interfacial impedance. Especially at low temperatures, the ion transport efficiency will be greatly reduced, affecting the battery's low-temperature performance and power output. Conversely, when the electrolyte retention coefficient P is too high (above 2.5 g / Ah), the excessive electrolyte will not only increase the battery's weight and volume and reduce energy density, but may also lead to the risk of electrolyte leakage and increase the possibility of side reactions between the electrolyte and electrode materials, thereby affecting the battery's cycle life and thermal stability.

[0043] By precisely controlling the electrolyte retention factor P between 0.8 g / Ah and 2.5 g / Ah, the electrolyte can fully wet the positive electrode active material layer, the safety coating on the surface of the positive electrode current collector, and the oxide solid electrolyte coating on the surface of the separator, ensuring smooth lithium-ion transport between the positive electrode, separator, and negative electrode. Simultaneously, the appropriate amount of electrolyte provides a favorable reaction environment for the first additive (acrylate monomer) and the second additive (crosslinking agent) contained in the electrolyte, enabling them to form a stable solid electrolyte interphase (SEI) film or polymer layer during battery operation, further reducing interfacial impedance and improving the battery's cycle stability and safety. This optimization of the electrolyte retention factor P, combined with the safety coating on the positive electrode current collector and the oxide solid electrolyte coating on the separator, effectively balances the battery's energy density, power performance, low-temperature characteristics, and thermal safety, avoiding the negative impact of improper electrolyte management on the battery's overall performance.

[0044] In some embodiments, the mass percentage of the first additive is 1% to 15% based on the total mass of the electrolyte (100%). Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.5% to 5%.

[0045] Specifically, by limiting the mass percentages of the first and second additives in the electrolyte, the formation process of the polymer network was controlled. The first additive, an acrylate monomer, was controlled within the range of 1% to 15%. This ensured that sufficient monomer molecules participated in the polymerization reaction to form the polymer backbone, thereby constructing an effective network structure to stabilize the electrolyte. Simultaneously, this range avoided incomplete polymerization due to excessively low monomer content, resulting in a loose network structure that could not function effectively; and also avoided a sharp increase in electrolyte viscosity due to excessively high content, which would hinder the transport efficiency of lithium ions in the electrolyte. Furthermore, the second additive, acting as a crosslinking agent, was limited within the range of 0.5% to 5%, ensuring that the polymer network could be fully crosslinked to form a three-dimensional structure with sufficient mechanical strength and stability. An appropriate amount of crosslinking agent effectively enhanced the toughness of the polymer network and its ability to solidify in the electrolyte, thereby improving the overall safety of the battery. Simultaneously, this range avoids the problem of insufficient network strength due to insufficient crosslinking agent content, as well as excessive crosslinking due to excessive content, resulting in an overly dense polymer network that affects electrolyte fluidity and lithium-ion transport efficiency at low temperatures. Through this synergistic constraint, the electrolyte system can form a structurally stable polymer network with high ion transport efficiency and strong adaptability to temperature changes, effectively solving the problem of unstable electrolyte performance caused by the imbalance of additive ratios in traditional solutions. This optimized electrolyte system, combined with the existing safety coating on the positive electrode current collector surface and the oxide solid electrolyte coating on the separator surface in lithium-ion batteries, can further improve the overall safety performance and low-temperature cycle performance of the battery, forming a more efficient and reliable battery system.

[0046] The mass percentage of the first additive can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, or 15%. Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.5% to 5%.

[0047] Further, the mass percentage of the second additive can be 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5% or 5%.

[0048] In some embodiments, the raw materials for the safety coating include one or more of lithium iron phosphate and ceramics.

[0049] The oxide solid electrolyte includes one or more of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconate (LLZO), lithium aluminum germanium phosphate (LAGP), and lithium lanthanum titanate (LLTO).

[0050] In some embodiments, the positive electrode active material layer includes a positive electrode active material, which includes a transition metal lithium oxide. The chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; Wherein, M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr; Specifically, the positive electrode active material can be one or more of the above-mentioned materials.

[0051] The positive electrode includes a positive current collector. In this application, there is no particular limitation on the type of positive current collector, which can be any known material suitable for use as a positive current collector, including aluminum, stainless steel, nickel plating, titanium, tantalum metal materials, as well as carbon cloth and carbon paper.

[0052] The positive electrode active material layer also includes a positive electrode conductive agent, a positive electrode binder, and a solvent.

[0053] In some embodiments, the present invention does not limit the type of positive conductive agent mentioned, and any known conductive agent may be used.

[0054] In some embodiments, the positive electrode conductive agent mentioned in this invention includes at least one of carbon materials such as natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene.

[0055] In some embodiments, the present invention does not limit the type of positive electrode binder, and any known positive electrode binder may be used.

[0056] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0057] In some embodiments, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one of graphite negative electrode, silicon-carbon composite negative electrode or lithium metal negative electrode.

[0058] The negative electrode active material layer also includes a negative electrode conductive agent, a negative electrode binder, a thickener, and a solvent; The negative electrode conductive agent includes at least one of the following carbon materials: natural graphite, artificial graphite, acetylene black, needle coke, carbon nanotubes, and graphene; the negative electrode binder includes styrene-butadiene latex; the thickener includes CMC; and the solvent includes deionized water.

[0059] The application does not impose any particular restrictions on the negative electrode current collector, as long as it can achieve the purpose of this application. For example, it can be copper foil, copper alloy foil, nickel foil, stainless steel foil, titanium foil, foamed nickel, foamed copper, or composite current collector, etc.

[0060] In some embodiments, the negative current collector comprises copper foil.

[0061] In the lithium-ion battery mentioned in this application, a separator is usually provided between the positive and negative electrodes to prevent short circuits. This application does not impose any particular restrictions on the material and shape of the separator, as long as it does not significantly impair the effectiveness of this application.

[0062] In some embodiments, the diaphragm includes a porous sheet-like or non-woven material with excellent liquid retention properties, and the diaphragm includes a resin or glass fiber diaphragm material, which includes, but is not limited to, polyolefins, aromatic polyamides, polytetrafluoroethylene, polyethersulfone, etc.

[0063] In some embodiments, the outer packaging of a lithium-ion battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc.

[0064] The outer packaging of lithium-ion batteries can also be a soft pack, such as a pouch. The material of the soft pack can be plastic, such as polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0065] This application does not impose any particular restrictions on the shape of the lithium-ion battery; it can be cylindrical, square, or any other arbitrary shape.

[0066] Another embodiment of the present invention provides an electrical device including the aforementioned lithium-ion battery.

[0067] Specifically, the electrical devices 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 are not limited to these.

[0068] The present invention will be further illustrated by the following examples.

[0069] Table 1 Table 2 Example 1 This embodiment illustrates the lithium-ion battery disclosed in this invention, and includes the following operational steps: Preparation of positive electrode The positive electrode current collector is a 10μm aluminum foil, mixed with ceramic, polyvinylidene fluoride (PVDF) binder, and 1-methyl-2-pyrrolidone (NMP) in a mass ratio of 50:2:48. After uniform mixing, a safety coating slurry is obtained. The safety coating slurry is uniformly coated on both sides of the positive electrode current collector. After baking and rolling, the coating thickness is measured by calipers. The thickness of the coating on one side is 1μm, and the total thickness of the coating on both sides is 2μm, thus obtaining a positive electrode current collector with a safety coating. The positive electrode active material lithium cobalt oxide, the positive electrode conductive agent acetylene black (SuperP) and polyvinylidene fluoride (PVDF) binder are mixed evenly at a mass ratio of 97:1.5:1.5, and then evenly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform positive electrode slurry 1. The safety coating surface of the positive electrode current collector is coated, and the positive electrode is obtained by baking and rolling.

[0070] Preparation of diaphragm The base membrane is a 6μm PE base membrane. The oxide solid electrolyte LATP, polyvinylidene fluoride (PVDF) binder, and 1-methyl-2-pyrrolidone (NMP) are mixed in a mass ratio of 50:2:48. After uniform mixing, an oxide solid electrolyte coating slurry is obtained. The coating slurry is uniformly coated on one side of the diaphragm. After baking and rolling, the coating thickness on one side is measured by calipers and found to be 1μm.

[0071] Preparation of negative electrode Artificial graphite (anode active material), acetylene black (Super P) (anode conductive agent), CMC (thickener), and SBR (anode binder) (anode binder) are mixed evenly in a mass ratio of 94:2:1.2:2.8 and then evenly dispersed with deionized water to form a uniform anode slurry. The mixed slurry is coated on both sides of a copper foil current collector, and then baked, rolled, and cut into sheets to obtain the anode.

[0072] Preparation of electrolyte a. Mix ethylene carbonate (EC), propylene carbonate (PC), propyl propionate (EP), and diethyl carbonate (DEC) in a mass ratio of 10:20:40:30 to form a mixed solvent. Remove water using a molecular sieve and set aside. Add 1M LiPF6 and mix thoroughly. Then add 0.5% azobisisobutyronitrile (AIBN) initiator, which accounts for the total mass ratio of solvent and lithium salt, to obtain a mixed solution. b. Add additives (the types and amounts of additives are shown in Table 1) to the mixture obtained in step a to obtain the electrolyte.

[0073] Manufacturing of lithium-ion batteries The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator in the middle of the positive and negative electrodes and the oxide solid electrolyte coating facing the positive electrode. After winding and welding the tabs, a bare cell is obtained. The bare cell is placed in an aluminum-plastic film for liquid injection and encapsulation. After liquid injection and encapsulation, the cell is cured at 60°C for 8 hours to form a gel. After the gel is formed, it is formed, resealed, and capacity tested to obtain a lithium-ion battery.

[0074] Examples 2-38 Examples 2-38 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that: The first additive type, A%, the second additive type, B%, the oxide solid electrolyte type, X, safety coating raw material, H, P, and the ratios of (H+X) / P, (A+B) / (H+X), H / X, and A / B are as specified in Tables 1 and 2, respectively.

[0075] Comparative Examples 1-37 Comparative Examples 1-37 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, with the following differences: The first additive type, A%, the second additive type, B%, the oxide solid electrolyte type, X, safety coating raw material, H, P, and the ratios of (H+X) / P, (A+B) / (H+X), H / X, and A / B are as specified in Tables 1 and 2, respectively.

[0076] Performance testing The following performance tests were performed on Examples 1-38 and Comparative Examples 1-37 prepared above: Thermal shock test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged at 25°C at a rate of 1C to the cutoff voltage and a cutoff current of 0.025C. They were then transferred to an oven and heated to 150°C at a rate of 5°C / min and kept constant for 60 minutes. The batteries were considered to have passed the test if they did not catch fire or explode. The number of test cells was 20.

[0077] 45℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to charge-discharge cycles at 45°C at a rate of 1C / 1C within the charge-discharge cutoff voltage range. The discharge capacity of the first cycle was recorded as C1, and the discharge capacity of the Nth cycle was recorded as C2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate R2 = C2 / C1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate R2 was 70% was recorded.

[0078] 0℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 0°C at a rate of 1C / 1C within the charge and discharge cutoff voltage range. The discharge capacity of the first cycle was recorded as Y1, and the discharge capacity of the Nth cycle was recorded as Y2. The capacity of the Nth cycle was divided by the capacity of the first cycle to obtain the cycle capacity retention rate of the Nth cycle, X2 = Y2 / Y1. The cycle number of the lithium-ion battery when the cycle capacity retention rate X2 was 70% was recorded.

[0079] The test results are entered into Table 3.

[0080] Table 3 As can be seen from the test results in Table 3, the overall test data (thermal shock pass rate, high and low temperature cycle life) of the embodiment are better than those of the comparative example. The core reason is that the safety coating of the positive electrode current collector and the solid electrolyte coating of the separator oxide form a dual channel for physical protection and ion transport in the embodiment of this application. This not only blocks heat propagation and prevents internal short circuits, but also makes up for the interface impedance problem caused by the safety coating. In addition, the acrylate monomers and crosslinking agents in the electrolyte are compounded according to the ratio specified in this application to form a highly stable elastic interface film, which inhibits electrolyte decomposition and transition metal dissolution, and inhibits lithium dendrite growth. At the same time, the embodiment of this application further limits the relevant parameters to meet 0.72≤(H+X) / P≤8, 0.5≤(A+B) / (H+X)≤8.89, 0.16≤H / X≤6.43, and 0.5≤A / B≤12, which achieves a precise match between coating thickness, liquid retention coefficient and additive ratio, and balances thermal safety and high and low temperature ion transport efficiency. In contrast, the comparative examples all have the problem of not meeting the above-mentioned relevant limits, and cannot form a synergistic protection and interface stability system, resulting in overall performance degradation.

[0081] Specifically, in the thermal shock tests of Examples 6, 9, 11-12, 15, 21, 25-26, 31, and 34, the number of passes was ≥14. Based on the parameter settings in Tables 1-2, all related examples met the requirements of a safety coating thickness ≥2.5 μm or an oxide solid electrolyte coating thickness ≥4 μm, demonstrating good physical protection. Furthermore, they satisfied the relationship 0.87 ≤ (A+B) / (H+X) ≤ 5.67, which is beneficial for fully utilizing the interfacial synergy between the additives and the coating. Similar effects were observed in Examples 6 (B=5%, sufficient crosslinking agent, strong thermal stability of the interfacial film) and 9 (X=5μm, strong ability of solid electrolyte coating to block heat propagation); only 8 particles passed the test in Example 22 and only 9 particles passed the test in Example 15. The reason is that the relationship or parameters between the two are at the critical values ​​set in this application. In Example 22, (H+X) / P=0.72 (close to the lower limit, insufficient solid conductive path), and in Example 15, P=2.8g / Ah (exceeding the upper limit of the liquid retention coefficient, excessive electrolyte can easily cause thermal runaway). Comparative Examples 1-15, lacking safety coatings, oxide electrolyte coatings, or electrolyte additives, could not provide synergistic protection, with only 2-7 samples passing the thermal shock test. For example, Comparative Example 1, which had no coatings or additives, had only 2 samples pass the test, thus verifying the conclusion that synergistic component parameters improve battery thermal safety.

[0082] The additives or coating thicknesses of Comparative Examples 16-25 deviated from the specified range, resulting in interface protection failure. For example, only 2 particles passed in Comparative Example 25 (P=3.5g / Ah, excess electrolyte), and although 13 particles passed in Comparative Example 23 (H=10μm, excessive coating caused local heat accumulation), it was still lower than Example 12 (15 particles). This was because the relationship H / X=10 exceeded the specified range (0.16≤H / X≤6.43), and the coating impedance was too high, causing side reactions.

[0083] Comparative Examples 26-29 showed that using non-acrylate monomers (such as isocyanate methacrylate) or crosslinking agents not specified in this application (such as N,N′-methylenebisacrylamide) failed to form a stable interfacial film, with only 3 particles passing through each. This indicates that additives not specified in this application cannot effectively improve the thermal stability of the interface.

[0084] Although the parameters of Comparative Examples 30 to 37 basically met the requirements, the relationships were unbalanced. For example, in Comparative Example 31, (H+X) / P=0.5 (insufficient solid-state pathway), only 6 samples passed the test, and in Comparative Example 32, (A+B) / (H+X)=14.29 (excessive additives blocked ion channels, causing local overheating), only 9 samples passed the test.

[0085] The low-temperature cycling cycles in the examples are generally between 360 and 537 cycles, far exceeding the low-temperature cycling cycles in the comparative examples. All examples satisfy the parameter relationships 1≤(H+X) / P≤5.33 and 0.4≤H / X≤5, achieving matching between the coating and the electrolyte and a reasonable coating thickness ratio, thereby reducing interfacial impedance. Among them, the groups with more than 500 cycles (such as Examples 9 and 15) all have the characteristics of X≥4μm (providing a fast ion channel) and A≥5% (ensuring the low-temperature elasticity of the interfacial film). However, the groups with a lower number of cycles (such as Examples 12 and 21) have H≥4μm and H / X≥5, resulting in an excessively thick safety coating that increases interfacial impedance, leading to a surge in lithium-ion transport resistance and accelerated capacity decay.

[0086] The comparative examples only achieved 228-460 low-temperature cycling cycles. The reasons for this are speculated to be: first, the coating is too thick, resulting in excessively high interfacial impedance, such as in Comparative Examples 23 (H=10μm) and 21 (X=10μm), which hinders low-temperature ion transport; second, the additive ratio is unbalanced, such as in Comparative Example 18 (B=0.1%, insufficient cross-linking leads to easy damage to the interfacial film) and Comparative Example 17 (A=20%, high electrolyte viscosity); and third, key parameters are missing, such as in Comparative Example 5, which has an oxide-free solid electrolyte coating, resulting in a significant decrease in low-temperature ion transport capability.

[0087] The specific test data above shows that by controlling the thickness H of the safety coating, the thickness X of the oxide solid electrolyte coating on the separator surface, the liquid retention coefficient P of the lithium-ion battery, the mass percentage A% of the first additive, and the mass percentage B of the second additive, while simultaneously satisfying 0.72≤(H+X) / P≤8, 0.5≤(A+B) / (H+X)≤8.89, 0.16≤H / X≤6.43, and 0.5≤A / B≤12, the potential increase in interface impedance introduced by the safety coating can be effectively balanced. This leads to the synergistic optimization of high battery safety, long cycle life, and wide temperature range performance through improvements in interface stability, ion transport, and thermal safety.

[0088] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium-ion battery, characterized in that, It includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode active material layer and a positive electrode current collector. A safety coating is disposed on the surface of the positive electrode current collector. The positive electrode active material layer is disposed on the surface of the safety coating. An oxide solid electrolyte coating is disposed on the surface of the separator facing the positive electrode. The electrolyte includes a first additive and a second additive, wherein the first additive includes an acrylate monomer and the second additive includes a crosslinking agent. The lithium-ion battery meets the following conditions: 0.72≤(H+X) / P≤8; 0.5≤(A+B) / (H+X)≤8.89; 0.16≤H / X≤6.43; 0.5 ≤ A / B ≤ 12; Where H is the thickness of the safety coating, in μm; X represents the thickness of the oxide solid electrolyte coating on the membrane surface, in μm; P is the liquid retention coefficient of the lithium-ion battery, with units of g / Ah; A% represents the mass percentage of the first additive in the electrolyte; B% represents the mass percentage of the second additive in the electrolyte.

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery meets the following conditions: 1≤(H+X) / P≤4.

67.

3. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery meets the following conditions: 0.87≤(A+B) / (H+X)≤5.

67.

4. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery meets the following conditions: 0.4≤H / X≤5.

5. The lithium-ion battery according to claim 1, characterized in that, The first additive and the second additive satisfy the following conditions: 1≤A / B≤10.

6. The lithium-ion battery according to claim 1, characterized in that, The raw materials for the safety coating include one or more of lithium iron phosphate and ceramics; and / or, The oxide solid electrolyte coating includes an oxide solid electrolyte, which comprises one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconate, lithium aluminum germanium phosphate, and lithium lanthanum titanate; and / or, The first additive includes one or more of butyl acrylate, butyl methacrylate, methyl acrylate, methyl methacrylate, pentafluoropropyl acrylate, trifluoroethyl acrylate, and trifluoroethyl methacrylate; and / or, The second additive includes one or more of pentaerythritol tetraacrylate, trimethylolpropane triacrylate, dipentaerythritol hexaacrylate, ethoxylated trimethylolpropane triacrylate, and polyethylene glycol diacrylate.

7. The lithium-ion battery according to claim 1, characterized in that, The thickness H of the safety coating is 0.5 μm ≤ H ≤ 5 μm; and / or, The thickness X of the oxide solid electrolyte coating is 0.5 μm ≤ X ≤ 5 μm; and / or, The liquid retention coefficient P of lithium-ion batteries is 0.8 g / Ah to 2.5 g / Ah.

8. The lithium-ion battery according to claim 1, characterized in that, Based on the total mass of the electrolyte as 100%, the mass percentage of the first additive is 1% to 15%. Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.5% to 5%.

9. The lithium-ion battery according to claim 1, characterized in that, The positive electrode active material layer includes a positive electrode active material, which includes a transition metal lithium oxide. The chemical formula of the transition metal lithium oxide is Li 1+x Ni y Co z M (1-y-z) O2, where -0.1≤x≤1; 0≤y≤1, 0≤z≤1, and 0≤y+z≤1; Wherein, M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr; The negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active material, and the negative electrode active material includes one of graphite negative electrode, silicon-carbon composite negative electrode or lithium metal negative electrode.

10. An electrical device, characterized in that, The lithium-ion battery includes any one of claims 1-9.

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