Lithium ion battery and electric device using the same

Abstract

In order to overcome the problems of poor cycle performance and safety performance of the existing lithium ion battery, the application 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, the positive electrode active material layer comprises a positive electrode active material and an oxide solid electrolyte, at least one side surface of the diaphragm is coated with an oxide solid electrolyte coating layer, the electrolyte comprises a first additive and a second additive, the first additive comprises mannitol carbonate sulfate, and the second additive comprises tris(trimethylsilyl)borate; the lithium ion battery satisfies the following relationship formulas: formula 1: 0.33<=B / A<=3; formula 2: 0.43<= (A+B) / (H+X) <=3.91; and formula 3: 0.26<= (B+X) / (A+H) <=2.33.

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, as one of the core technologies in modern electrochemical energy storage, occupy an important position in consumer electronics, new energy vehicles, and other fields due to their high energy density and excellent cycle stability. The stable operation of a battery system depends on the synergistic effect of key components such as the positive electrode, negative electrode active materials, electrolyte, and separator. Among the technical solutions for improving battery safety using solid electrolytes, oxide solid electrolytes can significantly improve battery thermal stability and build an efficient ion conduction network. However, the solid-liquid interface compatibility problem between oxide solid electrolytes and organic electrolytes has become a new bottleneck restricting the industrial application of this technology. Under high-temperature conditions, the surface of oxide solid electrolytes can catalyze the decomposition reaction of ester solvents in organic electrolytes, leading to the generation and accumulation of gaseous byproducts, which in turn causes a surge in interfacial impedance. Under low-temperature conditions, if the solid electrolyte coating on the separator surface is too thick, it will significantly increase the ion transport resistance, resulting in intensified battery polarization and significant capacity decay. Furthermore, there are multiple contradictions in the interaction between the key components in the battery system. The solid electrolyte coating of the separator and the solid electrolyte additive of the cathode oxide used to improve battery safety often lead to a decrease in the high temperature cycle stability of the battery while improving the battery's needle penetration safety and low temperature performance.

[0003] Therefore, there is an urgent need for a lithium-ion battery and electrical device that can improve high-temperature and low-temperature cycle performance and safety. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the issues of poor high-temperature and low-temperature cycle performance and low safety performance of lithium-ion batteries in the prior art, and to provide a lithium-ion battery and power device.

[0005] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows:

[0006] A lithium-ion battery is provided, comprising a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode active material layer, the positive electrode active material layer comprising a positive electrode active material and an oxide solid electrolyte. At least one side surface of the separator is coated with an oxide solid electrolyte coating. The electrolyte includes a first additive and a second additive. The first additive includes mannitol carbonate sulfate, and the second additive includes tris(trimethylsilane)borate.

[0007] Wherein, the mass percentage A% of the first additive in the electrolyte is 1%~5%, the mass percentage B% of the second additive in the electrolyte is 1%~5%, the thickness Hµm of the oxide solid electrolyte coating on the separator is 1µm~5µm, and the mass percentage X% of the oxide solid electrolyte in the positive electrode active material layer is 0.5%~3%;

[0008] The lithium-ion battery satisfies the following relationship:

[0009] Equation 1: 0.33 ≤ B / A ≤ 3;

[0010] Equation 2: 0.43≤(A+B) / (H+X)≤3.91;

[0011] Equation 3: 0.26≤(B+X) / (A+H)≤2.33.

[0012] Optionally, the lithium-ion battery satisfies at least one of the following relationships:

[0013] Equation 4: 0.4 ≤ B / A ≤ 2;

[0014] Equation 5: 0.83≤(A+B) / (H+X)≤2.67;

[0015] Equation 6: 0.38≤(B+X) / (A+H)≤1.2.

[0016] Optionally, the lithium-ion battery satisfies at least one of the following conditions:

[0017] (1) The mass percentage A% of the first additive in the electrolyte is 1.5%~3.5%;

[0018] (2) The mass percentage (B%) of the second additive in the electrolyte is 1.5% to 5%;

[0019] (3) The thickness Hµm of the oxide solid electrolyte coating on the diaphragm is 1.5µm~3.5µm;

[0020] (4) The mass percentage of oxide solid electrolyte in the positive electrode active material layer is 1%~2.5%.

[0021] Optionally, the membrane comprises a polyolefin porous membrane.

[0022] Optionally, the oxide solid electrolyte coating is applied to the surface of the separator near the positive electrode.

[0023] Optionally, the oxide solid electrolyte coating includes one or more of lithium aluminum titanium phosphate coating, lithium lanthanum zirconate coating, lithium aluminum germanium phosphate coating, and lithium lanthanum titanate coating.

[0024] 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.

[0025] Optionally, the mass percentage of the positive electrode active material in the positive electrode active material layer is 85% to 98%.

[0026] Optionally, the positive electrode active material includes one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate; 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≤0.2; 0.5≤y≤0.9, 0≤z≤0.4, and 0.9≤y+z≤1.0; where M is selected from one or more of Mn, Al, Mg, and Zr.

[0027] The present invention also provides an electrical device comprising the aforementioned lithium-ion battery.

[0028] The lithium-ion battery of this application achieves a balance of multiple performance characteristics through the synergistic regulation of the first additive mannitol carbonate sulfate (CBS), the second additive tris(trimethylsilane)borate ester (TMSB), and the oxide solid electrolyte components (the oxide solid electrolyte coating on at least one side of the separator and the oxide solid electrolyte in the positive electrode active material layer). CBS forms a dense SEI film with its bifunctional groups, improving high-temperature stability and needle penetration safety, but deteriorating low-temperature ion transport; TMSB can promote lithium salt dissociation and capture impurities, improving high and low temperature cycling performance without affecting safety. The oxide solid electrolyte coating on the separator acts as a physical barrier to enhance needle penetration safety, but increases the resistance to high and low temperature ion transport; the oxide solid electrolyte in the positive electrode active material layer constructs an efficient ion transport network, improving safety and low-temperature performance, but is prone to inducing high-temperature interface side reactions. Through functional group complementarity, CBS and TMSB can synergistically alleviate the negative impact of oxide solid electrolyte coating on at least one side of the separator and oxide solid electrolyte in the positive electrode active material layer on the battery. At high temperature, the two form a stable composite interface with the oxide solid electrolyte, inhibiting electrolyte decomposition and impedance growth. At low temperature, TMSB compensates for the impedance disadvantage of the dense SEI film of CBS by improving ionic conductivity. Simultaneously, precise control of A%, B%, H, and X% improves the overall performance of the battery. Equation 1: 0.33≤B / A≤3 precisely regulates the ratio of TMSB and CBS, ensuring that TMSB fully plays its role in enhancing ion conduction and improving low-temperature performance, effectively compensating for the low-temperature impedance disadvantage caused by the dense SEI film of CBS, and achieving synergistic function of the two additives. Equation 2: 0.43≤(A+B) / (H+X)≤3.91 balances the total chemical protection capacity of the electrolyte additives with the total amount of oxide solid electrolyte (H+X), so that the additives can offset the high-temperature interfacial side reactions caused by oxide solid electrolyte. Equation 3: 0.26≤(B+X) / (A+H)≤2.33 adapts the ratio of low-temperature beneficial components (TMSB, oxide solid electrolyte in the positive electrode active material layer) to low-temperature unfavorable components (CBS, oxide solid electrolyte on the separator), ensuring rapid ion transport kinetics at low temperatures. This invention solves the problem of solid-liquid interface instability caused by oxide solid electrolytes, achieving a balance between battery needle penetration safety and high and low temperature cycle performance, and significantly improving the overall performance and reliability of lithium-ion batteries in complex environments. Detailed Implementation

[0029] 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.

[0030] In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0031] An embodiment of 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, which comprises a positive electrode active material and an oxide solid electrolyte. At least one side of the separator is coated with an oxide solid electrolyte coating. The electrolyte includes a first additive and a second additive. The first additive includes mannitol carbonate sulfate, and the second additive includes tris(trimethylsilane)borate.

[0032] Wherein, the mass percentage A% of the first additive in the electrolyte is 1%~5%, the mass percentage B% of the second additive in the electrolyte is 1%~5%, the thickness Hµm of the oxide solid electrolyte coating on the separator is 1µm~5µm, and the mass percentage X% of the oxide solid electrolyte in the positive electrode active material layer is 0.5%~3%;

[0033] The lithium-ion battery satisfies the following relationship:

[0034] Equation 1: 0.33 ≤ B / A ≤ 3;

[0035] Equation 2: 0.43≤(A+B) / (H+X)≤3.91;

[0036] Equation 3: 0.26≤(B+X) / (A+H)≤2.33.

[0037] Specifically, the lithium-ion battery of this application achieves a balance of multiple performance characteristics through the synergistic regulation of the first additive mannitol carbonate sulfate (CBS), the second additive tris(trimethylsilane)borate ester (TMSB), and the oxide solid electrolyte (the oxide solid electrolyte coating on at least one side of the separator and the oxide solid electrolyte in the positive electrode active material layer). CBS forms a dense SEI film with its bifunctional groups, improving high-temperature stability and needle penetration safety, but deteriorating low-temperature ion transport; TMSB can promote lithium salt dissociation and capture impurities, improving high and low temperature cycling performance without affecting safety. The oxide solid electrolyte coating on the separator acts as a physical barrier to enhance needle penetration safety, but increases the resistance to high and low temperature ion transport; the oxide solid electrolyte in the positive electrode active material layer constructs an efficient ion transport network, improving safety and low-temperature performance, but is prone to inducing high-temperature interface side reactions. Through functional group complementarity, CBS and TMSB can synergistically alleviate the negative impact of oxide solid electrolyte coating on at least one side of the separator and oxide solid electrolyte in the positive electrode active material layer on the battery. At high temperature, the two form a stable composite interface with the oxide solid electrolyte, inhibiting electrolyte decomposition and impedance growth. At low temperature, TMSB compensates for the impedance disadvantage of the dense SEI film of CBS by improving ionic conductivity. Simultaneously, precise control of A%, B%, H, and X% improves the overall performance of the battery. Equation 1: 0.33≤B / A≤3 precisely regulates the ratio of TMSB and CBS, ensuring that TMSB fully plays its role in enhancing ion conduction and improving low-temperature performance, effectively compensating for the low-temperature impedance disadvantage caused by the dense SEI film of CBS, and achieving synergistic function of the two additives. Equation 2: 0.43≤(A+B) / (H+X)≤3.91 balances the total chemical protection capacity of the electrolyte additives with the total amount of oxide solid electrolyte (H+X), so that the additives can offset the high-temperature interfacial side reactions caused by oxide solid electrolyte. Equation 3: 0.26≤(B+X) / (A+H)≤2.33 adapts the ratio of low-temperature beneficial components (TMSB, oxide solid electrolyte in the positive electrode active material layer) to low-temperature unfavorable components (CBS, oxide solid electrolyte on the separator), ensuring rapid ion transport kinetics at low temperatures. This invention solves the problem of solid-liquid interface instability caused by oxide solid electrolytes, achieving a balance between battery needle penetration safety and high and low temperature cycle performance, and significantly improving the overall performance and reliability of lithium-ion batteries in complex environments.

[0038] In some embodiments, the lithium-ion battery satisfies at least one of the following relationships:

[0039] Equation 4: 0.4 ≤ B / A ≤ 2;

[0040] Equation 5: 0.83≤(A+B) / (H+X)≤2.67;

[0041] Equation 6: 0.38≤(B+X) / (A+H)≤1.2.

[0042] Specifically, when the lithium-ion battery satisfies equations 4, 5, and 6, the first additive, the second additive, the oxide solid electrolyte coating of the separator, and the oxide solid electrolyte in the positive electrode active material layer can better exert a synergistic effect, improving the battery's high-temperature cycling and thermal shock performance, as well as its low-temperature cycling performance.

[0043] When the B / A ratio is low, the relative content of TMSB is too low, and its boron-containing functional groups are insufficient to promote lithium salt dissociation and ion transport. This fails to effectively compensate for the high impedance problem caused by the formation of a dense SEI film by CBS at low temperatures. At the same time, its silane functional groups have a weakened ability to capture moisture and acidic substances, resulting in decreased interfacial compatibility and significantly deteriorated low-temperature cycling performance. When the B / A ratio is high, the relative content of TMSB is too high, and excessive boron-containing compounds are over-enriched at the interface. Although this increases ionic conductivity, it may lead to an abnormal increase in the electronic conductivity of the interfacial film, exacerbating the continuous oxidative decomposition of the electrolyte. In addition, excessive silane groups may trigger their own side reactions, which have an adverse effect on the interfacial stability at high temperatures.

[0044] When (A+B) / (H+X) is low, the total amount of additives is severely insufficient relative to the solid electrolyte content. CBS and TMSB cannot form a complete protective layer on the increased solid-liquid interface (caused by the oxide solid electrolyte coating of the separator and the oxide solid electrolyte of the positive electrode active material layer). This results in a large number of active sites on the surface of the oxide solid electrolyte being exposed, continuously catalyzing electrolyte decomposition at high temperatures, intensifying gas production, rapidly increasing interfacial impedance, and drastically reducing high-temperature cycling performance. When (A+B) / (H+X) is high, the total amount of additives is too high relative to the solid electrolyte content. Excessive CBS and TMSB undergo fierce competitive reduction in the limited interfacial area, forming an excessively thick and structurally complex interfacial film. This film has a huge ion migration impedance, severely hindering lithium ion transport, resulting in severely impaired battery rate performance, especially low-temperature discharge capability.

[0045] When (B+X) / (A+H) is low, the proportion of components beneficial to low-temperature performance (TMSB and oxide solid electrolyte in the positive electrode active material layer) is too low. The effect of TMSB on improving ionic conductivity and the advantages of the fast ion transport network constructed by the oxide solid electrolyte in the positive electrode active material layer are weakened, which cannot offset the high impedance effect caused by the dense SEI film of CBS and the thickness of the H coating. This results in a severe limitation of the migration rate of lithium ions at low temperatures, and a significant reduction in the low-temperature capacity and cycle life of the battery. When (B+X) / (A+H) is high, the proportion of components beneficial to low-temperature performance is too high. On the one hand, the excessive oxide solid electrolyte in the positive electrode active material layer exacerbates the interfacial side reactions at high temperatures in the positive electrode and catalyzes the decomposition of the electrolyte. On the other hand, the excessive TMSB may cause changes in the properties of the interfacial film. Its synergy with the excessive oxide solid electrolyte in the positive electrode active material layer may make the interfacial structure too loose or increase the electronic conductivity, which will reduce the protective properties of the interfacial film and have a negative impact on the high-temperature cycle stability.

[0046] In some embodiments, the lithium-ion battery satisfies at least one of the following conditions:

[0047] (1) The mass percentage A% of the first additive in the electrolyte is 1.5%~3.5%;

[0048] (2) The mass percentage (B%) of the second additive in the electrolyte is 1.5% to 5%;

[0049] (3) The thickness Hµm of the oxide solid electrolyte coating on the diaphragm is 1.5µm~3.5µm;

[0050] (4) The mass percentage of oxide solid electrolyte in the positive electrode active material layer is 1%~2.5%.

[0051] Specifically, the mass percentage A% of the first additive in the electrolyte includes, but is not limited to, 1.5%, 1.7%, 2%, 2.4%, 2.5%, 2.8%, 2.9%, 3.1%, and 3.5%. If A% is too low, the film-forming effect is insufficient, the interface protection is incomplete, and the electrolyte decomposition and transition metal dissolution cannot be effectively inhibited. If A% is too high, the formed SEI film is too dense, which seriously hinders lithium ion migration and significantly deteriorates the low-temperature performance.

[0052] The mass percentage (B%) of the second additive in the electrolyte includes, but is not limited to, 1.5%, 1.7%, 2%, 2.4%, 2.5%, 2.8%, 2.9%, 3.1%, 3.5%, 3.8%, 4.1%, 3.5%, and 5.0%. If the B% is too low, the enhancement of ion transport and the interfacial stabilization effect will be insufficient, and a stable interface with high ionic conductivity cannot be effectively constructed. If the B% is too high, excessive decomposition products may change the interfacial membrane properties, trigger additional side reactions, and pose a potential risk to long-term cycling stability.

[0053] The thickness Hµm of the oxide solid electrolyte coating on the separator includes, but is not limited to, 1.5µm, 1.8µm, 1.9µm, 2.3µm, 2.5µm, 2.7µm, 3µm, 3.2µm, and 3.5µm. If Hµm is too low, the physical barrier effect is insufficient, and the ability to suppress dendrite puncture and the improvement effect on thermal stability are limited, and the safety enhancement effect of solid electrolyte cannot be fully utilized. If Hµm is too high, the ion transport path is too long, the interface impedance increases significantly, especially at low temperature conditions, lithium ion migration is severely hindered. At the same time, the contact area between the overly thick coating and the electrolyte increases at high temperatures, side reactions are aggravated, and cycle performance is reduced.

[0054] The mass percentage X% of the oxide solid electrolyte in the positive electrode active material layer includes, but is not limited to, 1%, 1.3%, 1.6%, 1.8%, 2%, 2.1%, 2.4%, and 2.5%. If X% is too low, an effective continuous ion transport network cannot be formed in the positive electrode, and the effect of promoting ion migration at low temperatures and enhancing the integrity of the electrode structure is limited. If X% is too high, the excessive oxide solid electrolyte significantly increases the solid-liquid interface area, and the side reactions of catalytic electrolyte decomposition at high temperatures increase sharply, producing a large number of gaseous byproducts and impedance layers, which seriously deteriorates the high-temperature cycling performance.

[0055] In some embodiments, the membrane comprises a polyolefin porous base membrane.

[0056] Specifically, polyolefin porous membranes have high tensile strength and puncture strength, ensuring the stability of the battery structure, and their good electrochemical compatibility can reduce the risk of side reactions.

[0057] In some embodiments, the oxide solid electrolyte coating is applied to the surface of the separator near the positive electrode.

[0058] Specifically, applying the oxide solid electrolyte coating to the surface of the separator near the positive electrode can effectively enhance the mechanical strength and thermal stability of the separator. However, applying the oxide solid electrolyte coating to the side of the separator facing the negative electrode can easily cause side effects.

[0059] In some embodiments, the oxide solid electrolyte coating includes one or more of lithium aluminum titanium phosphate coating, lithium lanthanum zirconate coating, lithium aluminum germanium phosphate coating, and lithium lanthanum titanate coating.

[0060] Specifically, this type of oxide solid electrolyte coating exhibits excellent thermal stability and high ion conduction efficiency. It can suppress lithium dendrite growth, optimize solid-liquid interface compatibility, reduce interface impedance, and enhance the mechanical properties of the separator, thereby significantly improving battery safety and electrochemical cycle stability.

[0061] 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.

[0062] Specifically, this type of oxide solid electrolyte exhibits excellent thermal stability and a highly efficient ion conduction network, which can suppress lithium dendrite growth and significantly improve battery safety and electrochemical performance.

[0063] In some embodiments, the mass percentage of the positive electrode active material in the positive electrode active material layer is 85% to 98%.

[0064] Specifically, the mass percentage of the positive electrode active material in the positive electrode active material layer includes, but is not limited to, 85%, 89%, 92%, 93%, 95%, 97%, and 98%. The positive electrode active material layer also includes a positive electrode conductive agent, a positive electrode binder, and a solvent. There are no limitations on the type of positive electrode conductive agent mentioned in this invention; any known conductive agent can be used. There are also no limitations on the type of positive electrode binder mentioned in this invention; any known positive electrode binder can be used.

[0065] In some embodiments, the positive electrode active material includes one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate; 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≤0.2; 0.5≤y≤0.9, 0≤z≤0.4, and 0.9≤y+z≤1.0; where M is selected from one or more of Mn, Al, Mg, and Zr.

[0066] An embodiment of the present invention provides an electrical device including the lithium-ion battery described above.

[0067] For example, the aforementioned 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 thereto.

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

[0069] Example 1

[0070] This embodiment illustrates a lithium-ion battery disclosed in this invention, including the following operating steps:

[0071] Preparation of positive electrode

[0072] Lithium cobalt oxide (LCO), acetylene black (SuperP), and polyvinylidene fluoride (PVDF) binder were mixed uniformly at a mass ratio of 97:1.5:1.5 and then uniformly dispersed with 1-methyl-2-pyrrolidone (NMP) to form a uniform positive electrode slurry 1. 1% (1% of the total mass of LATP oxide solid electrolyte, acetylene black (SuperP), and PVDF binder) of LATP oxide solid electrolyte was added to the positive electrode slurry 1 and dispersed uniformly to obtain positive electrode slurry 2. The mixed positive electrode slurry 2 was coated on both sides of an aluminum foil current collector, and then baked, rolled, and cut into sheets to obtain the positive electrode sheet.

[0073] Preparation of negative electrode

[0074] The negative electrode active material graphite, negative electrode conductive agent acetylene black (Super P), thickener CMC and negative electrode binder SBR 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 negative electrode slurry. The mixed slurry is coated on both sides of the copper foil current collector, and then baked, rolled, and cut into sheets to obtain the negative electrode sheet.

[0075] Preparation of electrolyte

[0076] a. Mix ethylene carbonate (EC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC) in a mass ratio of 30:40:30 to form a mixed solvent. Remove water using a molecular sieve and set aside. Add 1M LiPF6 and mix thoroughly.

[0077] b. Add 1% by mass of the first additive (mannitol carbonate sulfate) and 2% by mass of the second additive (tris(trimethylsilane)borate) to the colorless and transparent liquid obtained in step a to obtain the electrolyte.

[0078] Preparation of diaphragm

[0079] The diaphragm uses a PE base membrane with a 2µm LATP coating on one side.

[0080] Manufacturing of lithium-ion batteries

[0081] The prepared positive electrode, separator, and negative electrode are stacked in sequence, with the separator in the middle of the positive and negative electrode, and the LATP coating facing the positive electrode. After winding and tab welding, a bare cell is obtained. The bare cell is placed in an aluminum-plastic film for liquid injection, encapsulation, etc., to obtain a lithium-ion battery.

[0082] Examples 2-31

[0083] Examples 2-31 illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that:

[0084] The values ​​of the first additive, A, the second additive, B, H, X, B / A, (A+B) / (H+X), and (B+X) / (A+H) in Examples 2-31 are all referenced in Table 1.

[0085] Comparative Examples 1-15

[0086] Comparative Examples 1-15 are used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, with the following differences:

[0087] The values ​​of the first additive, A, the second additive, B, H, X, B / A, (A+B) / (H+X), and (B+X) / (A+H) in Comparative Examples 1 to 15 are all referenced in Table 1.

[0088] Comparative Example 16

[0089] Comparative Example 16 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that:

[0090] The first additive, A, is vinyl sulfate.

[0091] Vinyl sulfate and CBS share a single identical functional group: the cyclic sulfate group.

[0092] Comparative Example 17

[0093] Comparative Example 17 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that:

[0094] The first additive, A, is ethylene carbonate.

[0095] Ethylene carbonate and CBS share a single identical functional group: cyclic carbonate group.

[0096] Comparative Example 18

[0097] Comparative Example 18 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that:

[0098] The second additive, B, is trimethylsilane.

[0099] Trimethylsilane and TMSB share a single identical functional group: trimethylsilyl.

[0100] Comparative Example 19

[0101] Comparative Example 19 is used to illustrate the lithium-ion battery disclosed in this invention, including most of the operations in Example 1, except that:

[0102] The second additive, B, is trimethylboronic acid ester.

[0103] Trimethylboronic acid ester and TMSB share a single identical functional group: the boronic acid ester group.

[0104] Table 1. Lithium-ion battery preparation parameters for the examples and comparative examples.

[0105]

[0106]

[0107] Performance testing

[0108] The following performance tests were performed on Examples 1-31 and Comparative Examples 1-19 prepared above:

[0109] 0℃ Cyclic Performance Test

[0110] 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 W2 = Y2 / Y1. The number of cycles of the lithium-ion battery when the cycle capacity retention rate W2 was 70% was recorded.

[0111] 45℃ Cyclic Performance Test

[0112] The lithium-ion batteries prepared in the above embodiments and comparative examples were charged and discharged at 45°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 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.

[0113] Pinprick test

[0114] Charge the lithium-ion batteries prepared in the above-mentioned examples and comparative examples to the cut-off voltage at a rate of 0.2C at 25°C, with a cut-off current of 0.025C. Use a steel needle (3mm) to vertically pierce the center of the fully charged battery at a speed of 25±5mm / s and keep it for 10 minutes after penetration. If the battery does not catch fire or explode, it passes the test. The total number of batteries tested is 20.

[0115] The above test results are shown in Table 2.

[0116] Table 2 Performance test results of lithium-ion batteries prepared in examples and comparative examples

[0117]

[0118]

[0119] As can be seen from the test results in Table 2, compared with the test results of the examples, in Comparative Example 1, there are no additives and oxide solid electrolyte components. The number of batteries passing the pinprick test is only 1. The number of cycles for the 0°C cycle capacity retention rate to reach 70% is only 230 cycles, and the number of cycles for the 45°C cycle capacity retention rate to reach 70% is only 243 cycles. This shows that the lack of additives and oxide solid electrolytes leads to a decrease in the battery safety performance and high and low temperature cycle performance.

[0120] The test results of Comparative Examples 2-9 show that when A% is less than 1%, a dense SEI film cannot be formed, leading to reduced high-temperature cycling stability and needle penetration safety. When A% is greater than 5%, the formed SEI film is too dense, reducing low-temperature ion transport efficiency and triggering side reactions, resulting in reduced high and low temperature cycling stability. When B% is less than 1%, lithium salt dissociation cannot be promoted, ionic conductivity decreases, and impurity capture ability is insufficient, leading to increased side reactions and reduced high and low temperature cycling performance. When B% is greater than 5%, excessive TMSB triggers interfacial side reactions, damaging interfacial layer stability and reducing high and low temperature cycling performance. When Hµm is less than 1µm, the mechanical strength and thermal stability of the separator are reduced, making it prone to dendrite puncture and internal short circuits, resulting in poor safety performance. Significant reduction occurs when Hµm exceeds 5µm. An excessively thick oxide solid electrolyte coating increases the lithium-ion transport path length and interfacial impedance, leading to decreased ion migration rate at low temperatures, resulting in increased polarization and capacity loss. At high temperatures, the increased interfacial contact area between the oxide solid electrolyte coating and the electrolyte accelerates interfacial side reactions and electrolyte decomposition, causing a decrease in cycle stability. When X% is below 0.5%, ionic conductivity and thermal stability decrease, leading to reduced safety performance and low-temperature cycle performance. When X% is above 3%, the oxide solid electrolyte in the positive electrode active material layer is prone to interfacial side reactions with the organic electrolyte at high temperatures, resulting in SEI film thickening and active material deactivation. This also exacerbates lithium-ion diffusion resistance at the positive electrode interface, worsening high-temperature cycle performance.

[0121] The test results of Comparative Examples 10-15 show that when the B / A ratio is below 0.33, the relative content of TMSB is too low and cannot effectively compensate for the high impedance problem caused by the formation of a dense SEI film by CBS at low temperatures, resulting in a significant deterioration in low-temperature cycling performance. When the B / A ratio is above 3, the relative content of TMSB is too high, and excessive boron-containing compounds are over-enriched at the interface, exacerbating the continuous oxidative decomposition of the electrolyte and worsening high and low temperature cycling performance. When (A+B) / (H+X) is below 0.43, the total amount of the two additives is severely insufficient relative to the oxide solid electrolyte, leading to the exposure of a large number of active sites on the surface of the oxide solid electrolyte. This continuously catalyzes the decomposition of the electrolyte at high temperatures, intensifies gas production, and causes a rapid increase in interfacial impedance, resulting in poor high-temperature cycling performance. Cyclic performance deteriorates sharply. When (A+B) / (H+X) is higher than 3.91, excessive CBS and TMSB undergo intense competitive reduction in the limited interface region, forming an excessively thick and complex interface film that hinders lithium-ion transport, leading to a decrease in cycle performance, especially low-temperature cycle performance. When (B+X) / (A+H) is lower than 0.26, the B% and X% are too low, severely limiting the migration rate of lithium ions at low temperatures and significantly reducing the battery's low-temperature cycle life. When (B+X) / (A+H) is higher than 2.33, the excess oxide solid electrolyte of the positive electrode active material layer exacerbates the interfacial side reactions at high temperatures, and the excess TMSB leads to changes in the properties of the interface film, resulting in a decrease in high-temperature cycle performance.

[0122] In Comparative Examples 16-19, other additives with the same single functional group as the additive in this application were used. Substitutes for CBS (Comparative Examples 16, 17) and TMSB (Comparative Examples 18, 19) showed a needle penetration count of 9-10 particles, a cycle life of 309-316 cycles at 0°C, and a cycle life of 351-359 cycles at 45°C. Both safety performance and high / low temperature cycle performance decreased. This indicates that only when CBS and TMSB have a bifunctional structure can they effectively synergistically complement each other to form a stable interface layer and efficient ion transport channels, thereby comprehensively improving battery performance. Additives with a single functional group cannot achieve this synergistic effect.

[0123] The test results of Examples 1-5 show that as the mass percentage A% of the first additive (CBS) in the electrolyte increases from 1% to 5%, the 0°C cycle capacity retention rate decreases from 458 cycles to 431 cycles. The dense SEI film formed by excessive CBS increases interfacial impedance and deteriorates low-temperature performance. However, the 45°C cycle capacity retention rate increases from 471 cycles to 512 cycles, and the number of needle penetrations increases from 15 to 20. The bifunctional groups of CBS (cyclic sulfate groups and cyclic carbonate groups) can effectively inhibit electrolyte decomposition and transition metal dissolution, improving high-temperature stability and safety. When A% is 1.5%~3.5%, the overall performance of the battery is relatively high.

[0124] In Examples 6-10, when the mass percentage (B%) of the second additive (TMSB) in the electrolyte increased from 1% to 5%, the cycle capacity retention at 0°C increased from 442 cycles to 489 cycles, and the cycle capacity retention at 45°C increased from 486 cycles to 513 cycles. This indicates that increasing TMSB can promote lithium salt dissociation through its boron-containing functional groups, and can also capture harmful substances through silane functional groups, improve interfacial ionic conductivity and stability, and improve high and low temperature cycle performance. Furthermore, TMSB has no significant negative impact on safety. When B% is between 1.5% and 5%, the overall performance of the battery reaches its optimal level.

[0125] In Examples 11-15, when the thickness Hµm of the oxide solid electrolyte coating on the separator increased from 1µm to 5µm, the number of needle penetrations increased from 16 to 20. Increasing the thickness of the oxide solid electrolyte coating can enhance the mechanical strength and thermal stability of the separator and improve safety; however, the number of cycles with capacity retention at 0°C decreased from 457 cycles to 431 cycles, and the number of cycles with capacity retention at 45°C decreased from 509 cycles to 482 cycles. The excessively thick coating increases the ion transport path and interface impedance, reducing the high and low temperature cycling performance; when the thickness of the oxide solid electrolyte coating is 1.5µm~3.5µm, the overall performance of the battery is higher.

[0126] In Examples 2 and 16-19, when the mass percentage X% of the oxide solid electrolyte in the positive electrode active material layer increases from 0.5% to 3%, the cycle capacity retention rate at 0°C increases from 445 cycles to 478 cycles, and the number of needle penetrations increases from 16 to 20. Increasing the oxide solid electrolyte in the positive electrode active material layer can form a continuous ion transport network, promote low-temperature ion migration, and enhance safety. However, the cycle capacity retention rate at 45°C decreases from 492 cycles to 462 cycles. Excess oxide solid electrolyte in the positive electrode active material layer catalyzes the decomposition of the electrolyte at high temperatures, producing byproducts and an impedance layer. When X% is 1%~2.5%, the overall performance of the battery is higher.

[0127] The test results of Examples 20-25 compared with those of Example 2 show that when B / A is low (B is 0.33), low-temperature cycling performance is affected; when B / A is high (B is 3), high and low temperature cycling performance is reduced; when B / A is in the range of 0.4 to 2, the overall performance of the battery is high. When (A+B) / (H+X) is relatively low at 0.43, high-temperature cycling performance is affected; when (A+B) / (H+X) is relatively high at 3.91, cycling performance, especially low-temperature cycling performance, is reduced. When (B+X) / (A+H) is relatively low at 0.26, low-temperature cycling life is affected; when (B+X) / (A+H) is relatively high at 2.33, high-temperature cycling performance is reduced; when (A+B) / (H+X) is in the range of 0.38 to 1.2, the overall performance of the battery is high.

[0128] The test results of Examples 26-31 show that when the type of oxide solid electrolyte and the type of oxide solid electrolyte coating on the diaphragm are other types (LLZO, LAGP, LLTO), the same improvement effect is achieved.

[0129] 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, The device includes a positive electrode, a negative electrode, a separator, and an electrolyte. The positive electrode includes a positive electrode active material layer, which contains a positive electrode active material and an oxide solid electrolyte. The surface of the separator near the positive electrode is coated with an oxide solid electrolyte coating. The electrolyte includes a first additive and a second additive. The first additive includes mannitol carbonate sulfate, and the second additive includes tris(trimethylsilane)borate. Wherein, the mass percentage A% of the first additive in the electrolyte is 1%~5%, the mass percentage B% of the second additive in the electrolyte is 1%~5%, the thickness Hµm of the oxide solid electrolyte coating on the separator is 1µm~5µm, and the mass percentage X% of the oxide solid electrolyte in the positive electrode active material layer is 0.5%~3%; The lithium-ion battery satisfies the following relationship: Equation 1: 0.33 ≤ B / A ≤ 3; Equation 2: 0.43≤(A+B) / (H+X)≤3.91; Equation 3: 0.26≤(B+X) / (A+H)≤2.

33.

2. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies at least one of the following relationships: Equation 4: 0.4 ≤ B / A ≤ 2; Equation 5: 0.83≤(A+B) / (H+X)≤2.67; Equation 6: 0.38≤(B+X) / (A+H)≤1.

2.

3. The lithium-ion battery according to claim 1, characterized in that, The lithium-ion battery satisfies at least one of the following conditions: (1) The mass percentage A% of the first additive in the electrolyte is 1.5% to 3.5%; (2) The mass percentage B% of the second additive in the electrolyte is 1.5% to 5%; (3) The thickness Hµm of the oxide solid electrolyte coating on the diaphragm is 1.5µm~3.5µm; (4) The mass percentage of oxide solid electrolyte in the positive electrode active material layer is 1%~2.5%.

4. The lithium-ion battery according to claim 1, characterized in that, The membrane comprises a polyolefin porous base membrane.

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

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

7. The lithium-ion battery according to claim 1, characterized in that, The positive electrode active material layer contains 85% to 98% by mass.

8. The lithium-ion battery according to claim 1, characterized in that, The positive electrode active material includes one or more of transition metal lithium oxide, lithium iron phosphate, lithium manganese oxide, lithium manganese iron phosphate, and lithium vanadium phosphate; 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≤0.2; 0.5≤y≤0.9, 0≤z≤0.4, and 0.9≤y+z≤1.0; where M is selected from one or more of Mn, Al, Mg, and Zr.

9. An electrical device, characterized in that, Including the lithium-ion battery as described in any one of claims 1 to 8.

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