Lithium ion battery and electric device

Abstract

The invention provides a lithium ion battery and an electric device, the lithium ion battery comprises a positive plate, a negative plate and an electrolyte, the positive plate comprises a positive active material layer, the positive active material layer comprises a positive active material and an oxide solid electrolyte, and the surface of the positive plate is provided with an oxide solid electrolyte layer; the electrolyte comprises a solvent, a lithium salt, a first additive and a second additive, the first additive comprises lithium difluorophosphate, and the second additive comprises tetraethylene silane; the lithium ion battery satisfies the following conditions: 0.72 < = (H + X) / P < = 8; 0.1 < = (A + B) / (H + X) < = 1.78; 0.16 < = H / X < = 6.43; 0.1 < = A / B < = 2.4; according to the lithium ion battery provided by the invention, the safety and the high and low temperature performance of the lithium ion battery are remarkably improved through multi-component cooperative regulation and control, further, when the lithium ion battery meets the limitation of the relational expression at the same time, the interface impedance can be reduced to the maximum extent, and the performance of the lithium ion battery can be improved through cooperation of multi-component parameters. 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, with their high energy density, low self-discharge rate, and long cycle life, have become the mainstream energy storage devices in consumer electronics and new energy vehicles. Their performance depends on the synergistic effect of four major components: the positive electrode, the negative electrode, the electrolyte, and the separator. Among them, the positive electrode is the key to affecting the battery's energy density and safety, but it also has corresponding problems in actual use. First, the crystal structure distortion during charge and discharge cycles leads to capacity decay. Second, the interfacial side reactions with the electrolyte cause loss of active materials and increased impedance. Third, the risk of thermal runaway under extreme conditions threatens the safety of use. Currently, the industry mainly modifies the positive electrode by element doping, core-shell structure design, and electrolyte formulation optimization to improve its structural stability and interfacial compatibility.

[0003] In existing technologies, the solution of incorporating oxide solid electrolyte (SSE) into the positive electrode active material layer and coating it on the surface of the positive electrode sheet is used to improve the overall performance of the battery. This solution works through a dual mechanism: the internal SSE particles can build a high-speed lithium-ion transport network, reduce the lithium-ion diffusion resistance at low temperature (0°C) to improve low-temperature charge and discharge capability; the SSE coating on the surface of the positive electrode sheet can act as an "interface reinforcement layer", enhance the stability of the interface between the positive electrode and the electrolyte, suppress interfacial side reactions and the dissolution of transition metal ions, and improve thermal safety.

[0004] However, while this technology improves low-temperature performance and thermal safety, it may lead to a slight decline in high-temperature cycle life. The core reason is that the introduction of SSE increases the solid-liquid interface area between the electrode and the electrolyte. These interfaces have high reactivity under high temperature and high pressure conditions, providing more reaction sites for electrolyte oxidation and decomposition, accelerating interfacial side reactions, internal gas generation and impedance growth, ultimately causing the battery's cycle life at high temperature (45℃) to decline compared to traditional structure batteries. Summary of the Invention

[0005] To address the issue that lithium-ion batteries cannot simultaneously achieve both safety and high / low temperature performance when oxide solid electrolytes are used as the cathode in existing technologies, a lithium-ion battery and power device are provided.

[0006] 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 and an electrolyte, wherein the positive electrode includes a positive active material layer, the positive active material layer includes a positive active material and an oxide solid electrolyte, and the surface of the positive electrode is provided with an oxide solid electrolyte layer; The electrolyte includes a solvent, a lithium salt, a first additive, and a second additive. The first additive includes lithium difluorophosphate, and the second additive includes tetraethylenesilane. The lithium-ion battery meets the following conditions: 0.72≤(H+X) / P≤8; 0.1≤(A+B) / (H+X)≤1.78; 0.16≤H / X≤6.43; 0.1 ≤ A / B ≤ 2.4; Where H is the thickness of the oxide solid electrolyte layer, in μm; X% represents the mass percentage of oxide solid electrolyte in the positive electrode active material layer; 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.

[0007] Optionally, the lithium-ion battery satisfies the following conditions: 1≤(H+X) / P≤4.67.

[0008] Optionally, the lithium-ion battery satisfies the following conditions: 0.19≤(A+B) / (H+X)≤1.

[0009] Optionally, the lithium-ion battery satisfies the following conditions: 0.4≤H / X≤5.

[0010] Optionally, the first additive and the second additive satisfy the following conditions: 0.2≤A / B≤2.

[0011] Optionally, the thickness H of the oxide solid electrolyte layer is 0.5 μm ≤ H ≤ 5 μm.

[0012] Optionally, in the positive electrode active material layer, the mass percentage of the oxide solid electrolyte is 0.5% ≤ X% ≤ 5%.

[0013] Optionally, the liquid retention coefficient of the lithium-ion battery is 0.8g / Ah≤P≤2.8g / Ah.

[0014] Optionally, based on the total mass of the electrolyte as 100%, the mass percentage of the first additive is 0.1% ≤ A% ≤ 1.5%; Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.25% ≤ B% ≤ 2.5%.

[0015] Optionally, the oxide solid electrolyte includes one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconate, lithium aluminum germanium phosphate, and lithium lanthanum titanate.

[0016] Optionally, the positive electrode active material includes 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; M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0017] Optionally, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active substance, and the negative electrode active substance includes one or more of graphite negative electrode, silicon-carbon composite negative electrode and 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 of this application are as follows: The lithium-ion battery provided in this application includes a positive electrode sheet comprising a positive electrode active material layer, which includes a positive electrode active material and an oxide solid electrolyte. An oxide solid electrolyte layer is also disposed on the surface of the positive electrode sheet. The electrolyte contains a first additive and a second additive. The SSE (solid-state electrolyte) incorporated into the positive electrode active material layer constructs a high-speed ion transport network, reducing lithium-ion diffusion resistance at low temperatures to ensure low-temperature performance. The oxide solid electrolyte layer on the electrode surface further serves as an interface reinforcement layer to suppress positive electrode side reactions and thermal runaway, improving basic safety. Simultaneously, the first additive, lithium difluorophosphate (LiPO2F2), in the electrolyte forms a LiF / Li-containing structure at the positive electrode. x PO y F z The stable interface film specifically addresses the problem that the solid-liquid interface generated after the introduction of oxide solid electrolytes is prone to oxidation and decomposition of electrolytes at high temperatures, ensuring high-temperature cycling stability. The second additive, tetraethylenesilane (TES), forms a tough SEI film on the negative electrode to suppress dendrites, further enhancing overall safety. Furthermore, through extensive preliminary experimental verification, this application controls the thickness H of the oxide solid electrolyte layer, the mass percentage of the oxide solid electrolyte X%, the liquid retention coefficient P of the lithium-ion battery, the mass percentage of the first additive A%, and the mass percentage of the second additive B, while simultaneously satisfying 0.72≤(H+X) / P≤8, 0.1≤(A+B) / (H+X)≤1.78, 0.16≤H / X≤6.43, and 0.1≤A / B≤2.4. This maximizes the reduction of interface impedance without affecting the low-temperature ion transport efficiency and thermal protection effect of the oxide solid electrolyte. In other words, through the synergy of multiple component parameters, the battery thermal safety, low-temperature discharge capacity, and high-temperature cycle life are simultaneously optimized. 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, and an electrolyte. The positive electrode includes a positive active material layer, which includes a positive active material and an oxide solid electrolyte. An oxide solid electrolyte layer is disposed on the surface of the positive electrode. The electrolyte includes a solvent, a lithium salt, a first additive, and a second additive. The first additive includes lithium difluorophosphate (LiPO2F2), and the second additive includes tetraethylenesilane (TES). The lithium-ion battery meets the following conditions: 0.72≤(H+X) / P≤8; 0.1≤(A+B) / (H+X)≤1.78; 0.16≤H / X≤6.43; 0.1 ≤ A / B ≤ 2.4; Where H is the thickness of the oxide solid electrolyte layer, in μm; X% represents the mass percentage of oxide solid electrolyte in the positive electrode active material layer; 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 lithium difluorophosphate additive is a highly efficient and multifunctional film-forming additive. It can undergo decomposition reactions at both the positive and negative electrode interfaces, participating in the formation of a layer rich in LiF and Li. x POy F z A stable and dense interfacial film with high ionic conductivity and good mechanical stability is formed, which effectively inhibits further decomposition of the electrolyte and dissolution of transition metal ions, thereby significantly improving the high-temperature cycle life and thermal stability of the battery. Meanwhile, its moderate interfacial impedance has minimal negative impact on low-temperature performance. The key to the synergistic effect between LiPO2F2 and the solid-state electrolyte (SSE) lies in the introduction of a large new interface, which is effectively passivated by the stable interfacial film formed by the decomposition of LiPO2F2. This prevents side reactions that may be exacerbated by contact between the SSE and the electrolyte, thus forming a robust positive electrode protection barrier.

[0023] Tetraethylenesilane additives primarily function at the anode interface. Their reduction and decomposition products can participate in the construction of an SEI film rich in organosilicon compounds and Li2O and Li2CO3. This SEI film has a dense structure and good flexibility, which can effectively adapt to the volume changes of silicon-based or graphite anodes during cycling, suppress the growth of lithium dendrites, thereby significantly improving the cycle life of the battery and the safety threshold under thermal abuse conditions (improving thermal shock performance). At the same time, the interfacial film formed by it has relatively low impedance and has little impact on the low-temperature performance of the battery. The synergy between TES and oxide solid electrolyte is reflected in the fact that the addition of SSE may change the local lithium ion flow distribution, while TES can enhance the stability of the anode interface. The tough SEI film formed by it can better suppress lithium dendrites and is a key component to ensure the stability of the anode interface of a high-safety battery.

[0024] The synergy between LiPO2F2 and TES allows LiPO2F2 to preferentially stabilize the positive electrode interface and inhibit oxidative decomposition, while TES preferentially acts on the negative electrode to form a tough SEI that suppresses dendrite formation. This achieves synchronous stability of the positive and negative electrode interfaces and avoids a chain reaction caused by the failure of one electrode. When LiPO2F2, TES, and solid electrolyte work together, the SSE strengthens the positive electrode bulk and interface from a physical and chemical perspective. LiPO2F2 and TES, through their chemical interactions, provide tough protection for the new interface formed by the SSE and the inherent negative electrode interface. The synergy of these three components enables lithium-ion batteries to achieve a good balance between high safety (excellent thermal shock), good low-temperature performance, and high stability.

[0025] Specifically, the lithium-ion battery provided in this application includes a positive electrode sheet comprising a positive electrode active material layer, which includes a positive electrode active material and an oxide solid electrolyte. An oxide solid electrolyte layer is also disposed on the surface of the positive electrode sheet. The electrolyte contains a first additive and a second additive. The SSE (solid-state electrolyte) incorporated into the positive electrode active material layer constructs a high-speed ion transport network, reducing lithium-ion diffusion resistance at low temperatures to ensure low-temperature performance. The oxide solid electrolyte layer disposed on the electrode surface further serves as an interface reinforcement layer to suppress positive electrode side reactions and thermal runaway, improving basic safety. Simultaneously, the first additive, lithium difluorophosphate (LiPO2F2), in the electrolyte forms a LiF / Li-containing structure at the positive electrode. x PO y F z The stable interface film specifically addresses the problem that the solid-liquid interface generated after the introduction of oxide solid electrolytes is prone to oxidation and decomposition of electrolytes at high temperatures, ensuring high-temperature cycling stability. The second additive, tetraethylenesilane (TES), forms a tough SEI film on the negative electrode to suppress dendrites, further enhancing overall safety. Furthermore, through extensive preliminary experimental verification, this application controls the thickness H of the oxide solid electrolyte layer, the mass percentage of the oxide solid electrolyte X%, the liquid retention coefficient P of the lithium-ion battery, the mass percentage of the first additive A%, and the mass percentage of the second additive B, while simultaneously satisfying 0.72≤(H+X) / P≤8, 0.1≤(A+B) / (H+X)≤1.78, 0.16≤H / X≤6.43, and 0.1≤A / B≤2.4. Under the premise of not affecting the low-temperature ion transport efficiency and thermal protection effect of the oxide solid electrolyte, the interfacial impedance is minimized to the maximum extent. That is, through the synergy of multiple component parameters, the battery thermal safety, low-temperature discharge capacity, and high-temperature cycle life are simultaneously optimized.

[0026] Experimental verification revealed that when (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. 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 the capacity utilization rate drops sharply. When (A+B) / (H+X) < 0.1, the additive is insufficient to cover the large newly added interface of the solid electrolyte, and the electrolyte continues to decompose at the active interface during high-temperature cycling, causing rapid capacity decay and impedance increase. When H / X > 1.78, excessive additive decomposition products form an overly thick interfacial film, which may hinder lithium-ion migration and affect overall performance. If H / X < 0.16, the electrode coating is too thin and cannot effectively reinforce the positive electrode interface, resulting in insufficient suppression of interfacial side reactions and decreased thermal safety. If H / X > 6.43, the overly thick coating may become a bottleneck for ion transport or increase internal resistance. When A / B < 0.1, a relative excess of TES may lead to an overly thick negative electrode SEI film or changes in composition, affecting efficiency. When A / B > 2.4, a relative excess of LiPO2F2 results in an overly thick positive electrode interfacial film, which may slightly affect kinetic performance.

[0027] In some embodiments, the lithium-ion battery satisfies the following conditions: 1≤(H+X) / P≤4.67.

[0028] Specifically, further limiting the (H+X) / P parameter of lithium-ion batteries to the range of 1≤(H+X) / P≤4.67, combined with the mixing of oxide solid electrolyte in the positive electrode active material layer, the setting of oxide solid electrolyte layer on the surface of the positive electrode sheet, and the presence of lithium difluorophosphate and tetraethylenesilane in the electrolyte, is beneficial to further enhance the synergistic effect and achieve better safety and high and low temperature performance.

[0029] In some embodiments, the lithium-ion battery satisfies the following conditions: 0.19≤(A+B) / (H+X)≤1.

[0030] Specifically, when the lithium-ion battery further satisfies 0.19≤(A+B) / (H+X)≤1, the following synergistic effects are achieved: mixing oxide solid electrolyte into the positive electrode active material layer (constructing a low-temperature, high-speed ion transport network), setting an oxide solid electrolyte layer on the positive electrode surface (suppressing positive electrode side reactions and thermal runaway), and combining lithium difluorophosphate in the electrolyte (forming a stable positive electrode interface film and improving high-temperature cycle stability) with tetraethylenesilane (constructing a tough negative electrode SEI film and suppressing dendrite growth). This is further achieved by matching 1≤(H+X) / P≤5.33, 0.16≤H / X≤6.43, and 0.1≤A / B≤2.4. By controlling the parameters, the total amount of dual additives in the electrolyte is matched with the relevant components of the oxide solid electrolyte. This ensures that the dual additives are sufficient to address the problems of easy oxidation and decomposition of the solid-liquid interface and dendrite growth of the negative electrode after the introduction of oxide solid electrolyte, while avoiding the increase in interface impedance or cost caused by excessive additives. Under the premise of ensuring low-temperature ion transport efficiency and thermal protection effect, the interface stability control is further enhanced, and the synergistic optimization effect of battery thermal safety, low-temperature discharge capacity and high-temperature cycle life is more balanced.

[0031] In some embodiments, the lithium-ion battery satisfies the following conditions: 0.4≤H / X≤5.

[0032] When the lithium-ion battery satisfies 0.4≤H / X≤5, it is beneficial to further optimize the performance. Specifically, when the lithium-ion battery satisfies 0.4≤H / X≤5, the precise ratio of the oxide solid electrolyte layer thickness H to the active layer doping amount X% is achieved. This ensures the dense protection of the surface electrolyte layer to fully suppress thermal runaway and side reactions, while avoiding the surge in interface impedance caused by excessive layer thickness or excessive doping amount. At the same time, it ensures the continuity of the ion transport network in the active layer to maintain low-temperature performance. Without affecting the synergistic effect of other functional components, the dual-effect efficiency of the oxide solid electrolyte is further optimized, so that the battery thermal safety, low-temperature discharge capacity and high-temperature cycle life can be better coordinated.

[0033] In some embodiments, the first additive and the second additive satisfy the following conditions: 0.2≤A / B≤2.

[0034] When the ratio of the first additive to the second additive is 0.2 ≤ A / B ≤ 2, the safety and high / low temperature performance of the lithium-ion battery can be further optimized. Specifically, the first additive can form a dense and stable interface film on the positive electrode surface in sufficient quantity, which can specifically suppress the high-temperature electrolyte oxidation and decomposition that is prone to occur at the solid-liquid interface after the introduction of oxide solid electrolyte, thus building a strong protective barrier for the positive electrode interface. The second additive can fully construct a high-toughness SEI film on the negative electrode surface, effectively suppressing lithium dendrite growth and SEI film rupture and shedding, and ensuring the stability of the negative electrode interface. This ratio range avoids the failure of the positive electrode interface protection caused by insufficient first additive, and also prevents the increase in interface impedance caused by its excessive amount. At the same time, it can ensure that the second additive can fully play its function of suppressing dendrites.

[0035] In some embodiments, the thickness H of the oxide solid electrolyte layer is 0.5 μm ≤ H ≤ 5 μm.

[0036] Specifically, when the thickness H of the oxide solid electrolyte layer is less than 0.5 μm, the mechanical strength is insufficient and the resistance to dendrite penetration decreases. When it is greater than 5 μm, the ion transport path is too long and the internal resistance increases significantly. Specifically, the thickness H of the oxide solid electrolyte layer can be 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm or 5 μm.

[0037] The raw material for the oxide solid electrolyte layer can be one or more of lithium aluminum titanium phosphate (LATP), lithium lanthanum zirconate (LLZO), lithium aluminum germanium phosphate (LAGP), and lithium lanthanum titanate (LLTO).

[0038] In some embodiments, the mass percentage of the oxide solid electrolyte in the positive electrode active material layer is 0.5% ≤ X% ≤ 5%.

[0039] Specifically, the mass percentage of the oxide solid electrolyte can be 0.5%, 1%, 2%, 3%, 4%, or 5%.

[0040] In some embodiments, the liquid retention coefficient of the lithium-ion battery is 0.8 g / Ah ≤ P ≤ 2.8 g / Ah.

[0041] Specifically, lithium-ion batteries limit the electrolyte retention coefficient P to 0.8 g / Ah ≤ P ≤ 2.8 g / Ah. This ensures that the electrolyte can fully wet the electrodes and separator, and, together with the ion transport network constructed by the oxide solid electrolyte in the positive electrode and separator, ensures lithium-ion diffusion efficiency and discharge capacity at low temperatures. This avoids the problems of reduced battery energy density and increased electrolyte side reactions at high temperatures caused by excessive electrolyte retention, while also preventing problems of insufficient interface wetting and obstructed ion transport caused by insufficient electrolyte retention.

[0042] Furthermore, the liquid retention coefficient P of the lithium-ion battery can be 0.8g / Ah, 1g / Ah, 1.2g / Ah, 1.5g / Ah, 2g / Ah, 2.3g / Ah, 2.5g / Ah or 2.8g / Ah.

[0043] In some embodiments, based on the total mass of the electrolyte as 100%, the mass percentage of the first additive is 0.1% ≤ A% ≤ 1.5%; Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.25% ≤ B% ≤ 2.5%.

[0044] Specifically, limiting the mass percentage of the first additive to 0.1%≤A%≤1.5% and the mass percentage of the second additive to 0.25%≤B%≤2.5% helps to ensure the synergistic stability of the positive and negative electrode interfaces, as well as improve battery thermal safety, low-temperature discharge capacity and high-temperature cycle life. Further, the mass percentage of the first additive can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.3%, or 1.5%; Further, the mass percentage of the second additive may be 0.25%, 0.3%, 0.35%, 0.5%, 0.8%, 1%, 1.3%, 1.5%, 1.8%, 2%, 2.3%, or 2.5%.

[0045] In some embodiments, the oxide solid electrolyte includes one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconate, lithium aluminum germanium phosphate, and lithium lanthanum titanate.

[0046] Specifically, in some embodiments, 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).

[0047] In some embodiments, the positive electrode active material includes 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; M is selected from one or more of Mg, Zn, Ga, Ba, Al, Cr, Sn, V, Mn, Sc, Ti, Nb, Mo, and Zr.

[0048] Specifically, the positive electrode active material can be one or more of the above-mentioned materials.

[0049] 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.

[0050] The positive electrode active material layer also includes a positive electrode conductive agent, a positive electrode binder, and a solvent.

[0051] In some embodiments, the present invention does not limit the type of positive conductive agent mentioned, and any known conductive agent may be used.

[0052] 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.

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

[0054] In some embodiments, the positive electrode binder includes at least one of polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polyimide, aromatic polyamide, cellulose, and nitrocellulose.

[0055] In some embodiments, the negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active substance, and the negative electrode active substance includes one or more of graphite negative electrode, silicon-carbon composite negative electrode and lithium metal negative electrode.

[0056] 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.

[0057] 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.

[0058] In some embodiments, the negative current collector comprises copper foil.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] Another embodiment of the present invention provides an electrical device including the aforementioned lithium-ion battery.

[0063] 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.

[0064] The present invention will be further illustrated by the following examples.

[0065] Table 1 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 active material lithium cobalt oxide, the positive electrode conductive agent acetylene black (SuperP) and polyvinylidene fluoride (PVDF) binder were 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. Add 1% by mass (1% of the total amount of positive electrode active material lithium cobalt oxide, positive electrode conductive agent acetylene black and polyvinylidene fluoride binder) of LATP oxidizing solid electrolyte to positive electrode slurry 1 and disperse it evenly to obtain positive electrode slurry 2. After coating the mixed positive electrode slurry 2 on both sides of aluminum foil current collector, it is baked to obtain positive electrode sheet 1. LATP oxide solid electrolyte, polyvinylidene fluoride (PVDF) binder, and 1-methyl-2-pyrrolidone (NMP) are mixed in a mass ratio of 20:2:78. After uniform mixing, an oxide solid electrolyte layer slurry is obtained. This slurry is then uniformly coated on both sides of the positive electrode sheet 1. After baking, the thickness of the LATP coating on one side is measured with calipers. The total thickness of the LATP coating on both sides is 2 μm. The sheet is then rolled and cut to obtain the positive electrode sheet described in this application.

[0066] 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 sheet.

[0067] 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 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.

[0068] Manufacturing of lithium-ion batteries The positive electrode, negative electrode, and separator are stacked in sequence, with the separator in the middle of the positive and negative electrodes. After winding and welding the tabs, a bare cell is obtained. The bare cell is then placed in an aluminum-plastic film for liquid injection, encapsulation, etc., to obtain a lithium-ion battery.

[0069] Examples 2-30 This embodiment is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Embodiment 1, with the following differences: The mass percentage of the first additive in the electrolyte (A / %), the mass percentage of the second additive in the electrolyte (B / %), the type of oxide solid electrolyte in the positive electrode active material layer (X / %), the type of oxide solid electrolyte in the positive electrode coating (Hμm), the thickness of the oxide solid electrolyte layer (Hμm), the electrolyte retention coefficient (Pg / Ah), and the ratios of (H+X) / P, (A+B) / (H+X), H / X, and A / B are all based on Table 1.

[0070] Comparative Examples 1-35 Comparative Examples 1-35 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 mass percentage of the first additive in the electrolyte (A / %), the mass percentage of the second additive in the electrolyte (B / %), the type of oxide solid electrolyte in the positive electrode active material layer (X / %), the type of oxide solid electrolyte in the positive electrode coating (H μm), the thickness of the oxide solid electrolyte layer (H μm), the electrolyte retention coefficient (P g / Ah), and the ratios of (H+X) / P, (A+B) / (H+X), H / X, and A / B are all based on Table 1.

[0071] Performance testing The following performance tests were performed on Examples 1-30 and Comparative Examples 1-35 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 battery cells tested was 20.

[0072] 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.

[0073] 0℃ Cyclic Performance Test The lithium-ion batteries prepared in the above embodiments and comparative examples were subjected to charge-discharge cycles at 0°C within the charge-discharge cutoff voltage range at a rate of 1C / 1C. 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 X2 = Y2 / Y1 of the Nth cycle. The number of cycles of the lithium-ion battery when the cycle capacity retention rate X2 was 70% was recorded.

[0074] The test results are entered into Table 2.

[0075] Table 2 As can be seen from the test results in Table 2, the test data of the embodiments are generally better than those of the comparative examples. The reason is that the lithium-ion batteries of Examples 1 to 30 simultaneously meet the requirements of mixing oxide solid electrolyte with positive electrode active material layer, setting oxide solid electrolyte layer on positive electrode surface, and having first additive and second additive in electrolyte. Moreover, the parameters (H+X) / P, (A+B) / (H+X), H / X, and A / B defined in this application are within the scope defined by this invention. Their thermal safety (thermal shock pass rate), low temperature (0°C) cycle life, and high temperature (45°C) cycle life are significantly better than those of the comparative examples. The comparative examples have a comprehensive performance degradation due to the lack of core components or parameters exceeding the defined range. This verifies the key role of multi-component synergy and parameter matching in this invention. As the thickness H of the oxide solid electrolyte layer increases from 0.5 μm (Example 10, 13 particles passed) to 5 μm (Example 12, 20 particles passed), the number of particles passing thermal shock gradually increases. The optimal thermal shock pass rate (20 particles) is achieved when H is 5 μm. This is because the thickness of the oxide solid electrolyte layer acts as a physical barrier. Increasing the thickness can more effectively block the direct contact between the positive electrode and the electrolyte, reducing the triggering source of thermal runaway. In Example 10, H is 0.5 μm, which has weak mechanical strength and limited resistance to dendrite penetration and thermal diffusion. In Example 12, H is 5 μm, which can completely cover the defects on the surface of the positive electrode, inhibit the dissolution of transition metal ions and the oxidative decomposition of the electrolyte, and can significantly reduce the risk of thermal runaway. The thermal shock pass rate was significantly improved when the mass percentage B% of the second additive increased from 0.25% (Example 4, 13 particles passed) to 2.5% (Example 6, 20 particles passed). This is because the second additive forms a silicon-rich and tough SEI film on the negative electrode. The increase in the mass percentage of the second additive makes the SEI film denser and more flexible, which can adapt to volume changes during negative electrode cycling and avoid lithium dendrite exposure and thermal reaction caused by SEI film rupture. In Example 4, B% was 0.25%, and the SEI film coverage was incomplete, making it easy for dendrites to puncture the separator at high temperatures. In Example 6, B% was 2.5%, and the SEI film protection was sufficient, eliminating the risk of short circuits caused by dendrites under thermal shock. As the mass percentage (A%) of the first additive in the electrolyte increased from 0.1% (Example 1, 597 weeks) to 1.5% (Example 3, 617 weeks), the cycle life at 45°C gradually increased. However, when A% exceeded 1.5% (Comparative Example 17, A=2%, 428 weeks), the cycle life actually decreased. The presumed reason is that at lower A% levels, LiPO2F2 cannot adequately cover the newly added solid-liquid interface of the oxide solid electrolyte, making the electrolyte prone to decomposition at the interface and leading to capacity decay. At A%=1.5%, a complete LiF / Li2O3 ... x PO y F z The interface film effectively suppresses side reactions. When A% is in excess, the interface film becomes too thick, which increases the lithium-ion migration resistance and shortens the cycle life. In Examples 7 and 9, the percentage of oxide solid electrolyte in the positive electrode active material layer, X%, increased from 0.5% (Example 7, 618 cycles) to 5% (Example 9, 705 cycles), resulting in a significant improvement in 0°C cycle life. This is presumably because, within the scope of this application, as X% increases, the amount of oxide solid electrolyte in the positive electrode active material layer increases, forming a denser high-speed lithium-ion transport network and reducing ion diffusion resistance at low temperatures. In Example 7, X% was 0.5%, resulting in a discontinuous transport network and low low-temperature ion transport efficiency; in Example 9, X% was 5%, resulting in a complete transport path, meeting the requirements of high-current charging and discharging at low temperatures, and achieving higher capacity retention. Comparative Examples 1-3, 6, and 11 showed low thermal shock pass rates, with 364-439 cycles at 45℃ and 339-439 cycles at 0℃, indicating poor performance. Among them, Comparative Examples 1, 2, 3, and 6, which used oxide-free solid electrolytes, had short low-temperature cycles due to the lack of a high-speed ion transport network. Furthermore, the absence of interfacial physical protection led to severe side reactions between the positive electrode and the electrolyte, resulting in a high risk of thermal runaway. Comparative Example 11, which used additives, lacked a stable film protection at the solid-liquid interface introduced by the oxide solid electrolyte. The electrolyte continued to decompose at high temperatures, resulting in only 364 cycles at 45℃. At the same time, the negative electrode lacked a tough SEI film and lithium dendrite growth, resulting in a thermal shock pass rate of only 7. Comparative Examples 20-21, 28, 30 and 34-35 have lower overall performance than the examples because their parameters exceed the limits of this application. Comparative Example 20 (H / X=20), which has an H / X ratio exceeding the range, has a 0°C cycle time of only 459 cycles due to the excessive thickness of the oxide solid electrolyte layer and insufficient mixing of oxide solid electrolyte in the positive electrode active material layer. Comparative Example 33 (H / X=0.11) had only 428 cycles at 45°C due to an excessively thin oxide solid electrolyte layer. The (A+B) / (H+X) ratio of Comparative Example 30 (2.86) exceeded the limit of this application. Both Comparative Example 33 and Comparative Example 31 (0.06) had poor cycle performance due to insufficient additives and severe interfacial side reactions. Comparative Example 34 (A / B = 3.25) has an A / B ratio that exceeds the limits of this application because of excessive first additive LiPO2F2 and excessively thick positive electrode interface film. Comparative Example 35 (A / B = 0.09) has an excessive second additive and excessively thick negative electrode SEI film, which also affects cycle life. Compared with the parameter settings of Examples 1 and 2, Comparative Examples 26 and 27, although satisfying the parameters and relationships defined in this application, used additives LiBOB and tetramethylsilane, which are not limited by this application, respectively. Their thermal shock safety and high / low temperature cycling performance were significantly lower than those of Examples 1 and 2. This is because LiBOB cannot form a stable LiF / Li ... x PO y F z The tetramethylsilane reduction product cannot form a tough SEI film, resulting in a sharp drop in performance.

[0076] In summary, the corresponding experimental data further verified that the present application achieves simultaneous optimization of battery thermal safety, low-temperature discharge capacity, and high-temperature cycle life through the synergy of multiple component parameters.

[0077] 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, and an electrolyte. The positive electrode includes a positive active material layer, which includes a positive active material and an oxide solid electrolyte. An oxide solid electrolyte layer is disposed on the surface of the positive electrode. The electrolyte includes a solvent, a lithium salt, a first additive, and a second additive. The first additive includes lithium difluorophosphate, and the second additive includes tetraethylenesilane. The lithium-ion battery meets the following conditions: 0.72≤(H+X) / P≤8; 0.1≤(A+B) / (H+X)≤1.78; 0.16≤H / X≤6.43; 0.1 ≤ A / B ≤ 2.4; Where H is the thickness of the oxide solid electrolyte layer, in μm; X% represents the mass percentage of oxide solid electrolyte in the positive electrode active material layer; 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: 0.19≤(A+B) / (H+X)≤1.

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: 0.2≤A / B≤2.

6. The lithium-ion battery according to claim 1, characterized in that, The thickness H of the oxide solid electrolyte layer is 0.5μm≤H≤5μm.

7. The lithium-ion battery according to claim 1, characterized in that, In the positive electrode active material layer, the mass percentage of the oxide solid electrolyte is 0.5% ≤ X% ≤ 5%.

8. The lithium-ion battery according to claim 1, characterized in that, The liquid retention coefficient of lithium-ion batteries is 0.8 g / Ah ≤ P ≤ 2.8 g / Ah.

9. The lithium-ion battery according to claim 1, characterized in that, Based on the total mass of the electrolyte being 100%, the mass percentage of the first additive is 0.1% ≤ A% ≤ 1.5%; Based on the total mass of the electrolyte as 100%, the mass percentage of the second additive is 0.25% ≤ B% ≤ 2.5%.

10. The lithium-ion battery according to claim 1, characterized in that, The oxide solid electrolyte includes one or more of lithium aluminum titanium phosphate, lithium lanthanum zirconate, lithium aluminum germanium phosphate, and lithium lanthanum titanate.

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

12. The lithium-ion battery according to claim 1, characterized in that, The negative electrode includes a negative electrode active material layer, the negative electrode active material layer includes a negative electrode active substance, and the negative electrode active substance includes one or more of graphite negative electrode, silicon-carbon composite negative electrode and lithium metal negative electrode.

13. An electrical appliance, characterized in that, The lithium-ion battery includes any one of claims 1-12.

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