A high specific energy lithium-ion battery

Abstract

The application discloses a high specific energy lithium ion battery, which comprises a positive electrode, a negative electrode, a diaphragm and an electrolyte, the negative electrode is a metal lithium negative electrode or a negative electrode without active material, the electrolyte contains 10-70wt% of fluoroethylene carbonate, a first additive and a second additive, the first additive is a sulfur-containing amide heterocyclic compound, the second additive is a cyclic sulfate compound, the first additive accounts for 0.1-5.0wt% of the total mass of the electrolyte, and the second additive accounts for 0.1-5.0wt% of the total mass of the electrolyte. The high specific energy lithium ion battery provided by the application has excellent high-temperature storage and rate cycle performance, excellent safety performance and service life.

Description

Technical Field

[0001] This invention relates to the field of electrolytes, and more specifically to an energy storage electrolyte and a high-energy-density lithium-ion battery using the same. Background Technology

[0002] The global "decarbonization revolution" continues to drive the construction and upgrading of renewable energy networks in modern life, providing new opportunities for the development of electrochemical energy storage devices. Lithium-ion batteries, due to their advantages such as high energy density, good stability, long cycle life, low self-discharge, and no memory effect, have stood out from many energy storage devices and become one of the most important technologies in the field of electrochemical energy storage. In recent years, the application scenarios of lithium-ion batteries have rapidly expanded, gradually penetrating from portable electronic devices to electric vehicles, smart grids, and other fields. This has also placed higher demands on the safety and energy density of lithium-ion batteries.

[0003] Lithium metal batteries, including those with lithium metal anodes or anodes without active materials, possess the most negative potential and ultra-high specific capacity, making them the ultimate choice for improving the energy density of lithium-ion batteries. Unlike the extraction / intercalation mechanism of lithium ions within silicon-based and graphite structures, lithium metal batteries employ a deposition / stripping mechanism of lithium ions on the current collector surface. However, uneven deposition of lithium ions can lead to the formation of lithium dendrites and their uncontrolled growth, as well as poor stability of the solid electrolyte interface (SEI), resulting in decreased battery cycle life and severely reduced safety performance. The safety and lifespan issues caused by dendrite lithium growth greatly restrict the application of lithium metal batteries in large-scale energy storage.

[0004] To address the aforementioned issues, extensive research and exploration have been conducted on modification strategies to combat lithium dendrite formation in lithium metal batteries. Fluorinated ethylene carbonate (FEC) can be used to stabilize the lithium metal anode, decomposing to generate LiF to form a rich SEI interface and polyvinyl chloride (VC) organic components, thus improving the cycle performance of lithium metal batteries. However, FEC does not significantly improve the regulation of the anode interface deposition current or promote uniform lithium metal deposition, and therefore cannot fundamentally solve the lithium dendrite problem. Furthermore, in lithium metal anode batteries, the amount of FEC typically exceeds 10%, and high FEC content increases gas generation during high-temperature storage and leads to a continuous increase in battery impedance, posing significant challenges to the battery's high-temperature storage and rate performance. A paper (DOI:10.1002 / adma.202305470) proposes using 4,6-dimethyl-2-mercaptopyrimidine (DMP), a typical leveling agent used in the copper deposition industry, to suppress lithium dendrite formation. The DMP leveling agent reshapes the Li... +The solvation structure alters lithium deposition behavior by forming steric barriers, thereby inducing uniform lithium deposition. However, the DMP leveling agent does not participate in the formation of the solid electrolyte interface, and cannot guarantee the uniformity and stability of the interface. At the same time, the planar DMP molecular layer formed by the leveling agent on the lithium metal surface, while suppressing side reactions, also affects the migration rate of lithium ions, thus failing to simultaneously ensure the battery's storage stability and rate cycling performance.

[0005] Therefore, developing an additive or additive composition that promotes uniform lithium-ion deposition, inhibits the formation and growth of lithium dendrites, and maintains good high-temperature storage performance and rate cycling characteristics, while ensuring excellent battery safety performance and lifespan, is of great practical significance for the application of high-energy-density lithium metal batteries. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention proposes a high-energy-density lithium-ion battery that can suppress the formation and growth of lithium dendrites, while also exhibiting excellent high-temperature storage performance and rate cycling characteristics, ensuring the battery's superior safety performance and lifespan.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A high-energy-density lithium-ion battery includes a positive electrode, a negative electrode, a separator, and an electrolyte. The negative electrode is a metallic lithium negative electrode or a negative electrode without active materials. The electrolyte contains 10-70 wt% fluoroethylene carbonate (FEC). The electrolyte further includes a first additive and a second additive.

[0009] The first additive is selected from at least one of the sulfur-containing oroamide heterocyclic compounds with the structure shown in formula (A):

[0010]

[0011] In formula (A), R1, R2, and R3 are independently selected from hydrogen, C1-C6 alkyl, C3-C6 cycloalkyl, C2-C6 alkenyl, C2-C6 alkoxy, cyano, phenyl, or phenoxy, and the hydrogen in R1, R2, and R3 may optionally be substituted with a halogen; n is selected from 0, 1, or 2; m is selected from 0 or 1.

[0012] The second additive is selected from at least one of the cyclic sulfate compounds with the structures shown in formula (B-I), formula (B-II), and formula (B-III):

[0013]

[0014] In formula (B-Ⅰ), m is selected from 0, 1 or 2;

[0015] In formula (B-Ⅱ), z is selected from 0, 1 or 2;

[0016] In formula (B-Ⅲ), R4, R5, R6, and R7 are independently selected from hydrogen, C1-C10 alkyl, C3-C10 cycloalkyl, C2-C10 alkenyl, C2-C10 alkynyl, C1-C10 alkoxy, phenyl, or phenoxy, and the hydrogen in R4, R5, R6, and R7 may optionally be substituted with a halogen.

[0017] The first additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte; the second additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.

[0018] Regarding the structures of the first and second additives, preferably...

[0019] In formula (A), R1, R2, and R3 are independently selected from hydrogen, C1-C4 alkyl, C3-C6 cycloalkyl, C2-C3 alkenyl, C2-C3 alkynyl, C1-C3 alkoxy, cyano, phenyl, or phenoxy, and the hydrogen in R1, R2, and R3 may optionally be substituted with a halogen; n is selected from 0, 1, or 2; m is selected from 0 or 1.

[0020] In formula (B-Ⅰ), m is selected from 0 or 1;

[0021] In formula (B-Ⅱ), z is selected from 0, 1 or 2;

[0022] In formula (B-Ⅲ), R4, R5, R6, and R7 are independently selected from hydrogen, C1-C3 alkyl, C3-C4 cycloalkyl, C2-C3 alkenyl, and C2-C3 alkynyl, and the hydrogen in R4, R5, R6, and R7 may optionally be substituted with fluorine.

[0023] More preferably,

[0024] In formula (A), R1, R2, and R3 are independently selected from hydrogen, C1-C4 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, cyano, and phenyl, and the hydrogen in R1, R2, and R3 may optionally be substituted with fluorine; n is selected from 1; and m is selected from 0 or 1.

[0025] Most preferably, the first additive is selected from at least one of the following structures:

[0026]

[0027] The second additive is selected from at least one of the following structures:

[0028]

[0029] When the first additive of this invention is used at 0.1–5.0 wt% of the total electrolyte mass, the sulfonamide heterocyclic group possesses heteroatom adsorption capacity and strong coordination. During lithium deposition, the additive preferentially anchors the lithium, forming a protective molecular layer on the lithium surface, thus preventing the active lithium metal from undergoing continuous side reactions with the solvent. Therefore, this effectively delays the random nucleation and uneven deposition of lithium atoms. Furthermore, the solvated clusters formed by the first additive are highly likely to repel the polarized solute Li through repulsive forces. + The additive pushes lithium ions into the adjacent area, thereby inducing random deposition of lithium ions repelling the lithium anode. This balancing effect promotes uniform lithium deposition and inhibits lithium dendrite growth, effectively extending the working life of lithium metal batteries. When the second additive is used at 0.1–5.0 wt% of the total electrolyte mass, it effectively reduces the lithium metal interface, forming an interface film rich in inorganic components. This reduces solvent consumption and enhances interface uniformity and stability. The synergistic application of both additives effectively reduces initial impedance, giving the battery excellent high-temperature storage and rate cycling performance. It also significantly improves lithium plating in lithium metal batteries, inhibits the formation and growth of lithium dendrites, and ensures excellent battery safety and lifespan.

[0030] However, the interfacial components formed by the first additive have poor stability and lithium-ion conductivity. Adding a small amount can create a uniform electric field and induce uniform lithium-ion deposition; however, excessive addition may directly affect interfacial lithium-ion conductivity, impacting rate performance and cycle life. The interfacial components formed by the second additive are mainly inorganic, exhibiting superior ion conductivity, which can reduce impedance and improve high-temperature storage and cycle stability. However, excessive addition resulting in an overly thick interfacial component will still increase interfacial impedance, affecting battery cycle life and increasing the risk of lithium plating.

[0031] To establish a balanced interfacial ion conduction and a uniform interfacial electric field, effectively suppressing lithium plating, preferably, the first additive accounts for 0.1–5.0 wt% of the total electrolyte mass; the second additive accounts for 0.1–5.0 wt% of the total electrolyte mass. More preferably, the first additive accounts for 0.1–2.0 wt% of the total electrolyte mass; the second additive accounts for 0.1–2.0 wt% of the total electrolyte mass. Most preferably, the first additive accounts for 0.1–1.0 wt% of the total electrolyte mass; the second additive accounts for 0.5–1.5 wt% of the total electrolyte mass.

[0032] Regarding the content of fluoroethylene carbonate, preferably, the fluoroethylene carbonate accounts for 15 to 60 wt% of the total mass of the electrolyte.

[0033] The electrolyte of the present invention further comprises a main lithium salt, which is preferably selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium difluorophosphate-based fluorophosphate, and lithium difluorophosphate-based fluoroborate, and its molar concentration is 0.1 to 4.0 mol / L; more preferably, the main lithium salt is selected from at least one of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, or lithium bis(trifluoromethanesulfonyl)imide, and the molar concentration of the main lithium salt is 0.8 to 2.0 mol / L.

[0034] The electrolyte further comprises the base solvent, which is selected from at least one of C3-C6 carbonate compounds, C3-C8 carboxylic acid ester compounds, sulfone compounds, and ether compounds. Preferably, the C3-C6 carbonate compound is selected from at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, difluorodimethyl ester, methyl ethyl fluoride, diethyl fluoride, fluoropropylene carbonate, and diethyl fluoride; and the C3-C8 carboxylic acid ester compound is selected from at least one of ethyl acetate, methyl propyl carbonate, propyl propionate, γ-butyrolactone, γ-valerolactone, or ethyl difluoroacetate.

[0035] The electrolyte further comprises the basic additive, which is selected from at least one of vinyl sulfate, sulfonate compounds, unsaturated carbonate compounds, phosphate compounds, acid anhydride compounds, nitrile compounds, or fluorinated lithium salt compounds, and the amount of any basic additive is 0.1 to 5.0 wt% of the total mass of the electrolyte. Preferably, the sulfonate compound is selected from at least one of 1,3-propenesulfonyl lactone and propenesulfonate lactone; the unsaturated carbonate compound is selected from at least one of ethylene ethylene carbonate and vinylene carbonate; the phosphate compound is selected from tris(trimethylsilyl)phosphate; the acid anhydride compound is selected from at least one of succinic anhydride, glutaric anhydride, citrate anhydride, and maleic anhydride; the nitrile compound is selected from at least one of succinic anhydride, adiponitrile, hexanetrionitrile, and cyclohexylbenzene; and the fluorinated lithium salt compound is selected from at least one of lithium difluorophosphate, lithium bis(fluorosulfonyl)imide, lithium difluorophosphate bis(oxalate) or lithium difluorooxalate borate. The amount of any one basic additive is 0.1 to 2.0 wt% of the total mass of the electrolyte, and the basic additive is different from the main lithium salt.

[0036] In one specific embodiment, the main lithium salt is LiPF6, accounting for 10% to 15% of the total mass of the electrolyte; the fluoroethylene carbonate solvent accounts for 15% to 60% of the total mass of the electrolyte; the base solvent is selected from at least one of ethylene carbonate, dimethyl carbonate, and diethyl carbonate, more preferably dimethyl carbonate; when the base solvent is diethyl carbonate, the volume ratio of fluoroethylene carbonate to diethyl carbonate solvent is 1:1; the sulfur-containing orthoamide heterocyclic compound is preferably A1 or A9, accounting for 0.1% to 5% of the total mass of the electrolyte; the cyclic sulfate ester compound is preferably B4 or B6, accounting for 0.1% to 5% of the total mass of the electrolyte; the base additive is selected from at least one of ethylene sulfate, 1,3-propenesulfonyl lactone, vinylene carbonate, and lithium difluorophosphate bis(oxalate), accounting for 0.1% to 5% of the total mass of the electrolyte. The use of sulfur-containing orthoamide heterocyclic compounds and cyclic sulfate compounds can effectively inhibit the formation and growth of lithium dendrites in high-energy-density batteries, enabling the batteries to have excellent high-temperature storage performance and rate cycle performance, and ensuring excellent safety performance and service life.

[0037] The lithium metal anode of the present invention is a pure lithium anode or a lithium alloy, wherein the lithium alloy is an alloy formed by lithium and at least one metal selected from aluminum, zinc, magnesium, indium, and gallium, and the mass content of lithium accounts for 5-80% of the lithium alloy content. Preferably, the lithium alloy is an alloy formed by lithium and at least one metal selected from aluminum, zinc, and indium, and the mass content of lithium accounts for 10-60% of the lithium alloy content.

[0038] The active material of the positive electrode can be any commonly used positive electrode material for lithium-ion batteries. Preferably, the active material of the positive electrode is selected from at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobalt oxide, lithium iron phosphate, lithium manganese iron phosphate, or other active materials capable of lithium-ion intercalation / deintercalation. The nickel-cobalt-manganese ternary material is Li(Ni) x Co y Mn z O2, x≥0.5, y>0, z>0, x+y+z=1; the nickel-cobalt-aluminum ternary material is Li(Ni x Co y Al z )O2, x≥0.8, y>0, z>0, x+y+z=1.

[0039] The high-energy-density lithium-ion battery of the present invention has an energy density of over 320Wh / kg.

[0040] The high-energy-density lithium-ion battery of the present invention has an operating voltage range of 2.5 to 4.4V.

[0041] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0042] The high-energy-density lithium-ion battery provided by this invention contains a combination of sulfur-containing orthoamide heterocyclic compounds and cyclic sulfate compounds in its electrolyte. The sulfur-containing orthoamide heterocyclic compounds possess heteroatom adsorption capacity and strong coordination properties. During lithium deposition, they can preferentially anchor themselves on the lithium metal surface to form a protective molecular layer, inhibiting continuous side reactions between the active lithium metal and the solvent. This effectively delays the random nucleation and uneven deposition of lithium ions, thereby suppressing the formation and growth of lithium dendrites in the high-energy-density lithium-ion battery. However, the sulfur-containing orthoamide heterocyclic compounds cannot participate in the formation of a solid electrolyte membrane, and the planar molecular layer formed on the lithium metal surface, while suppressing side reactions, also affects the migration rate of lithium ions. Therefore, it cannot simultaneously ensure the battery's storage stability and rate cycle performance. The cyclic sulfate compounds can form a dense inorganic component interface film on the negative electrode surface, which not only facilitates lithium ion migration but is also less prone to breakage, effectively solving the problems of insufficient interfacial stability and poor lithium-ion conductivity associated with sulfur-containing orthoamide heterocyclic compounds. Therefore, the synergistic effect of the two can effectively suppress the formation and growth of lithium dendrites in high-energy-density batteries, improve the high-temperature storage performance and rate cycling performance of high-energy-density batteries, and ensure the excellent safety performance and service life of batteries. Detailed Implementation

[0043] The present invention will be further described below with reference to specific embodiments, but the invention is not limited to these specific embodiments. Those skilled in the art should recognize that the present invention covers all alternatives, improvements, and equivalents that may be included within the scope of the claims.

[0044] I. Electrolyte Preparation

[0045] Preparation of the basic electrolyte: In an argon-filled glove box (moisture content < 5 ppm, oxygen content < 10 ppm), the basic solvents dimethyl carbonate (DMC) and fluoroethylene carbonate (FEC) were uniformly mixed at a mass ratio of DMC:FEC = 5:5 (volume ratio). Then, lithium hexafluorophosphate (LiPF6) was slowly added to the mixed solution until the molar concentration of LiPF6 was 1.0 mol / L, thus obtaining the basic electrolyte, in which FEC accounted for approximately 45% of the total mass of the electrolyte.

[0046] Example 1

[0047] The electrolyte of this embodiment is obtained by adding 0.1% of compound A1 and 0.5% of compound B1 to the base electrolyte.

[0048] Example 2

[0049] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 0.5% of compound B1 to the base electrolyte.

[0050] Example 3

[0051] The electrolyte of this embodiment is obtained by adding 1.0% of compound A1 and 0.5% of compound B1 to the base electrolyte.

[0052] Example 4

[0053] The electrolyte of this embodiment is obtained by adding 2.0% of compound A1 and 0.5% of compound B1 to the base electrolyte.

[0054] Example 5

[0055] The electrolyte of this embodiment is obtained by adding 5.0% of compound A1 and 0.5% of compound B1 to the base electrolyte.

[0056] Example 6

[0057] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 0.1% of compound B1 to the base electrolyte.

[0058] Example 7

[0059] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 1.0% of compound B1 to the base electrolyte.

[0060] Example 8

[0061] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 2.0% of compound B1 to the base electrolyte.

[0062] Example 9

[0063] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 5.0% of compound B1 to the base electrolyte.

[0064] Example 10

[0065] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 1.0% of compound B2 to the base electrolyte.

[0066] Example 11

[0067] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 1.0% of compound B4 to the base electrolyte.

[0068] Example 12

[0069] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 1.0% of compound B6 to the base electrolyte.

[0070] Example 13

[0071] The electrolyte of this embodiment is obtained by adding 0.5% of compound A1 and 1.0% of compound B8 to the base electrolyte.

[0072] Example 14

[0073] The electrolyte of this embodiment is obtained by adding 0.5% of compound A4 and 1.0% of compound B4 to the base electrolyte.

[0074] Example 15

[0075] The electrolyte of this embodiment is obtained by adding 0.5% of compound A4 and 1.0% of compound B6 to the base electrolyte.

[0076] Example 16

[0077] The electrolyte of this embodiment is obtained by adding 0.5% of compound A7 and 1.0% of compound B4 to the base electrolyte.

[0078] Example 17

[0079] The electrolyte of this embodiment is obtained by adding 0.5% of compound A7 and 1.0% of compound B6 to the base electrolyte.

[0080] Example 18

[0081] The electrolyte of this embodiment is obtained by adding 0.5% of compound A9 and 1.0% of compound B4 to the base electrolyte.

[0082] Example 19

[0083] The electrolyte of this embodiment is obtained by adding 0.5% of compound A9 and 1.0% of compound B6 to the base electrolyte.

[0084] Example 20

[0085] The electrolyte of this embodiment is obtained by adding 0.5% of compound A10 and 1.0% of compound B4 to the base electrolyte.

[0086] Example 21

[0087] The electrolyte of this embodiment is obtained by adding 0.5% of compound A10 and 1.0% of compound B6 to the base electrolyte.

[0088] Comparative Example 1

[0089] The basic electrolyte (without additives) was used as the electrolyte in this comparative example.

[0090] Comparative Example 2

[0091] The electrolyte of this comparative example was obtained by adding only 0.5% of compound A2 to the base electrolyte.

[0092] Comparative Example 3

[0093] The electrolyte of this comparative example was obtained by adding only 1.0% of compound B2 to the base electrolyte.

[0094] Comparative Example 4

[0095] The electrolyte of this comparative example was obtained by adding 0.5% of compound A2 and 1.0% of compound PS to the basic electrolyte.

[0096] Comparative Example 5

[0097] The electrolyte of this comparative example was obtained by adding 0.5% of compound A2 and 1.0% of compound DTD to the base electrolyte.

[0098] Comparative Example 6

[0099] To the base electrolyte, 1.0% of compound VC and 0.5% of compound A2 were added to obtain the electrolyte of this comparative example.

[0100] Comparative Example 7

[0101] To the base electrolyte, 1.0% of compound PS and 1.0% of compound B2 were added to obtain the electrolyte of this comparative example.

[0102] Comparative Example 8

[0103] The electrolyte of this comparative example was obtained by adding 1.0% of compound DTD and 1.0% of compound B2 to the base electrolyte.

[0104] Comparative Example 9

[0105] The electrolyte of this comparative example was obtained by adding 0.5% of compound A9 and 1.0% of compound PS to the base electrolyte.

[0106] II. Electrochemical Performance Testing

[0107] The electrochemical performance of the combination of the first and second additives in the lithium metal system was tested, and the specific procedures are as follows:

[0108] The electrolytes obtained in the above embodiments and comparative examples were used to prepare soft-pack lithium-ion batteries (capacity 1500mAh) for testing. Each lithium-ion battery includes a positive electrode, a negative electrode, a separator, an electrolyte, and battery auxiliary materials. The positive electrode active material is a nickel-cobalt-manganese ternary material, specifically Li(Ni) ternary material. 0.6 Co 0.1 Mn 0.3O2. The negative electrode active material is lithium metal. The preparation process is as follows: the positive electrode sheet, separator and negative electrode sheet are wound together into a core, sealed with aluminum-plastic film and then baked to ensure that the electrode moisture meets the requirements. After baking, the cell is injected with electrolyte, and after standing, formation, capacity testing and aging processes, the finished soft-pack cell is obtained.

[0109] The high-energy-density lithium-ion battery (soft-pack cell) obtained was subjected to performance testing. The specific test items and methods are as follows:

[0110] (1) 60℃ high temperature storage test: Charge the battery to 100% SOC and store it in an oven at 60±2℃ for 28 days. Test the volume before and after storage to obtain the volume expansion rate of the single cell before and after storage at 60℃; test the DCR value after storage at room temperature and calculate the percentage value of the initial DCR, which is called the discharge DCR change rate.

[0111] (2) 25℃ ambient temperature cycle test: The battery is cycled in a room temperature environment of 25±1℃ with charge and discharge currents of 0.33C / 0.33C and 1C / 2C. The discharge capacity is calculated every week until the discharge capacity is 80% of the initial discharge capacity. The cycle ends, the number of cycles is recorded, and the cell is disassembled at the end of the life to observe the lithium plating.

[0112] The test results are shown in Table 1 below:

[0113] Table 1. Battery electrochemical performance test results

[0114]

[0115]

[0116] According to the test results of Examples 1 to 21 in Table 1 above, the combined use of sulfur-containing amide heterocyclic compounds and cyclic sulfate compounds can significantly improve the low-rate (0.33C / 0.33C) and high-rate (1C / 2C) cycle performance of lithium metal batteries at room temperature, improve the lithium plating problem, and thus inhibit the formation and growth of lithium dendrites; at the same time, it also takes into account excellent high-temperature storage performance, and improves the safety performance and service life of the battery.

[0117] Comparisons of Comparative Examples 1 and 2 & 3 show that the first additive, the thiocyanate heterocyclic compound, used alone, can effectively suppress lithium plating and improve low-rate and high-rate cycle life. However, it increases initial impedance, resulting in slight lithium plating during high-rate cycling. Comparisons of Comparative Examples 1 and 4 & 5 show that the second additive, the cyclic sulfate compound, used alone, can reduce initial impedance, significantly improve high-temperature storage performance, and enhance low-rate and high-rate cycle life. However, because it cannot achieve uniform current distribution under high-rate charging and discharging, it leads to severe lithium plating during rate cycling.

[0118] By comparing Examples 11, 12, 18, 19 and Comparative Examples 2, 3, 4, 5, it can be found that the combination of the first additive and the second additive has a synergistic effect. Compared with the use of the two additives alone, it further reduces the initial impedance of the battery, improves the interface stability, and effectively suppresses the lithium plating problem, thereby improving the high-temperature storage performance and cycle life of the battery. In particular, the combination of the two additives has a significant gain effect on high-temperature storage performance and low-rate cycling.

[0119] By comparing Examples 6-13 and Comparative Examples 6 and 7, as well as Examples 18 and 19 and Comparative Examples 8 and 9, it can be found that the combination of sulfur-containing orthoamide heterocyclic compounds and cyclic sulfate compounds, compared with the combination of sulfur-containing orthoamide heterocyclic compounds and DTD and PS, results in a more stable interfacial film formed by cyclic sulfate compounds with high ionic conductivity, which reduces cell impedance, forms a stable negative electrode interface, improves high-temperature storage and rate cycling performance, suppresses lithium plating, and enhances the overall performance of the battery.

[0120] In summary, the high-energy-density battery provided by this invention, with its electrolyte containing a combination of sulfur-containing orthoamide heterocyclic compounds and cyclic sulfate compounds, can not only reduce the initial impedance of the high-energy-density battery and improve its rate cycle performance, effectively suppress the formation and growth of lithium dendrites in the high-energy-density battery, but also take into account the high-temperature storage stability of the high-energy-density battery, thereby effectively achieving excellent safety performance and service life of the high-energy-density battery.

Claims

1. A high-energy-density lithium-ion battery, comprising a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the negative electrode is a metallic lithium negative electrode or a negative electrode without active material, and the electrolyte contains 10-70 wt% fluoroethylene carbonate, characterized in that: The electrolyte also contains a first additive and a second additive: The first additive is selected from at least one of the sulfur-containing oroamide heterocyclic compounds shown in formula (A): In formula (A), R1, R2, and R3 are independently selected from hydrogen, C1-C6 alkyl, C3-C6 cycloalkyl, C2-C6 alkenyl, C2-C6 alkynyl, C1-C6 alkoxy, cyano, phenyl, or phenoxy, and the hydrogen in R1, R2, and R3 may optionally be substituted with a halogen; n is selected from 0, 1, or 2; m is selected from 0 or 1. The second additive is selected from at least one of the cyclic sulfate compounds with the structures shown in Formula (B-I), Formula (B-II), and Formula (B-III): In formula (B-Ⅰ), m is selected from 0, 1 or 2; In formula (B-Ⅱ), z is selected from 0, 1 or 2; In formula (B-Ⅲ), R4, R5, R6, and R7 are independently selected from hydrogen, C1-C10 alkyl, C3-C10 cycloalkyl, C2-C10 alkenyl, C2-C10 alkynyl, C1-C10 alkoxy, phenyl, or phenoxy, and the hydrogen in R4, R5, R6, and R7 may optionally be substituted with a halogen. The first additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte; the second additive accounts for 0.1 to 5.0 wt% of the total mass of the electrolyte.

2. The high-energy-density lithium-ion battery according to claim 1, characterized in that: In formula (A), R1, R2, and R3 are independently selected from hydrogen, C1-C4 alkyl, C3-C6 cycloalkyl, C2-C3 alkenyl, C2-C3 alkynyl, C1-C3 alkoxy, cyano, phenyl, or phenoxy, and the hydrogen in R1, R2, and R3 may optionally be substituted with a halogen; n is selected from 0, 1, or 2; m is selected from 0 or 1. In formula (B-Ⅰ), m is selected from 0 or 1; In formula (B-Ⅱ), z is selected from 0, 1 or 2; In formula (B-Ⅲ), R4, R5, R6, and R7 are independently selected from hydrogen, C1-C3 alkyl, C3-C4 cycloalkyl, C2-C3 alkenyl, and C2-C3 alkynyl, and the hydrogen in R4, R5, R6, and R7 may optionally be substituted with fluorine.

3. The high-energy-density lithium-ion battery according to claim 2, characterized in that: In formula (A), R1, R2, and R3 are independently selected from hydrogen, C1-C4 alkyl, C2-C3 alkenyl, C2-C3 alkynyl, cyano, and phenyl, and the hydrogen in R1, R2, and R3 may optionally be substituted with fluorine; n is selected from 1; and m is selected from 0 or 1.

4. The high-energy-density lithium-ion battery according to claim 3, characterized in that: The first additive is selected from at least one of the structures shown in the following formula: The second additive is selected from at least one of the structures shown in the following formula:

5. The high-energy-density lithium-ion battery according to any one of claims 1-4, characterized in that: The first additive accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte, and the second additive accounts for 0.1 to 2.0 wt% of the total mass of the electrolyte.

6. The high-energy-density lithium-ion battery according to claim 1, characterized in that: The fluoroethylene carbonate accounts for 15-60 wt% of the total mass of the electrolyte.

7. The high-energy-density lithium-ion battery according to claim 1, characterized in that: The lithium metal anode is pure lithium or a lithium alloy, wherein the lithium alloy is an alloy formed of lithium and at least one metal selected from aluminum, zinc, magnesium, indium, and gallium, and the lithium mass accounts for 5 to 80% of the lithium alloy mass.

8. The high-energy-density lithium-ion battery according to claim 1, characterized in that: The electrolyte further comprises a main lithium salt, which is selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonyl)imide, lithium difluorophosphate-based fluorophosphate, and lithium difluorophosphate-based fluoroborate, and its molar concentration is 0.1 to 4.0 mol / L.

9. The high-energy-density lithium-ion battery according to claim 1, characterized in that: The electrolyte also contains a basic additive, which is selected from at least one of vinyl sulfate, sulfonate compounds, unsaturated carbonate compounds, phosphate compounds, acid anhydride compounds, nitrile compounds or fluorinated lithium salt compounds, and the amount of any basic additive is 0.1 to 5.0 wt% of the total mass of the electrolyte.

10. The high-energy-density lithium-ion battery according to claim 1, characterized in that: The positive electrode is selected from at least one of nickel-cobalt-manganese ternary materials, nickel-cobalt-aluminum ternary materials, lithium cobalt oxide, lithium iron phosphate, and lithium manganese iron phosphate.

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