Electrolyte additive, electrolyte and lithium ion battery

Abstract

The invention discloses an electrolyte additive of a lithium metal battery, an electrolyte thereof and a lithium ion battery. The electrolyte additive provided by the invention comprises a cationic organic large group and an anionic nitrate ion organic nitrate additive. NO32 in the structure can be preferentially reduced on the lithium metal negative electrode side to generate high-quality SEI rich in inorganic compounds. Then, the organic cation large groups inhibit the growth of lithium dendrites while maintaining the lithium nucleation rate through the characteristic adsorption effect, and finally uniform spherical deposition morphology is obtained.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of batteries, in particular to an electrolyte additive, an electrolyte prepared from the electrolyte additive and a lithium ion battery comprising the electrolyte. BACKGROUND

[0002] The large-scale application of renewable energy sources such as wind and solar energy has created an urgent demand for efficient energy storage technologies. At the same time, the rapid development of electric vehicles has further driven the research and development of high-energy-density, long-cycle-life batteries. Lithium-ion batteries, with their high energy density, long cycle life, and mature industrial chain, have dominated the market in electric vehicles, consumer electronics, and energy storage systems. However, there are still several key issues that limit their further development and application. The cycle life and decay problems are still prominent, especially under high-rate charging and discharging and extreme temperature conditions, the structural stability of electrode materials decreases, and the irreversible loss of active lithium increases, leading to rapid capacity decay. Safety issues, such as the risk of thermal runaway, still exist under conditions such as overcharging, short-circuiting, or mechanical damage, which can cause fires or even explosions. In addition, the cost of battery materials cannot be ignored, especially the price fluctuations and supply chain security issues of key raw materials such as cobalt, making it difficult to further reduce battery costs. The lack of fast-charging capability is also a real bottleneck, as the limited diffusion speed of lithium ions in electrode materials can easily lead to the formation of lithium dendrites and the destruction of electrode structures during high-current charging. In terms of environmental adaptability, lithium-ion batteries perform poorly in low-temperature environments and materials age faster in high-temperature environments, limiting their application in extreme weather conditions. Finally, the sustainability of resources and recycling systems are not yet perfect, and the recycling of large amounts of retired batteries faces technical and economic challenges, which may have potential environmental impacts. These problems collectively constitute the main obstacles to the development of lithium-ion battery technology, and breakthroughs in material innovation, structural design, and system management are urgently needed to address them. Solving the problem of lithium metal anodes can effectively improve the cycle performance of batteries and effectively suppress the growth of lithium dendrites and the continuous consumption of electrolyte, thereby improving the safety performance of batteries and reducing the frequency of accidents. During the battery cycle, the dynamic deposition / dissolution behavior of lithium metal anodes can cause the continuous rupture and reconstruction of the solid electrolyte interface (SEI), leading to a series of interface instability problems. The dynamic instability of the SEI layer is mainly due to the non-equilibrium evolution of its multiple components, such as Li2O, LiF, Li2CO3, and ROCO2Li, during the cycle process, while the non-uniformity of the mass transfer process leads to uneven distribution of lithium ion flux. This dual effect significantly changes the local electric field distribution, according to the classical nucleation theory (ΔG* ∝ γ³ / Δμ²), the nucleation energy barrier of lithium deposition is closely related to the interfacial energy (γ) and the chemical potential difference (Δμ). In areas with weak mechanical strength of the SEI, a locally enhanced electric field is formed due to the sharp tip effect, and lithium ions are preferentially reduced and deposited here, further exacerbating the dendritic tendency of the surface topography. This positive feedback mechanism not only causes the continuous consumption of active lithium and electrolyte, but also may cause internal short circuits and other safety hazards.Therefore, the interface engineering method of the electrolyte additive with low cost and simple process is used to regulate the lithium deposition dynamics and improve the lithium deposition morphology, and the key strategy for realizing the uniform lithium deposition is to construct a homogeneous SEI layer with high mechanical strength, high lithium ion conductivity and rich in inorganic components (such as LiF and Li3N), which provides an important theoretical basis and technical approach for developing safe and high-energy-density lithium metal batteries. SUMMARY

[0003] To achieve the above-mentioned purpose, the application provides an electrolyte additive, an electrolyte prepared from the electrolyte additive and a lithium ion battery comprising the electrolyte, the anion group of the electrolyte additive can generate a SEI rich in inorganic compounds on the lithium negative electrode, and then the cation large group makes the lithium deposit in a spherical shape through specific adsorption, the electrolyte additive effectively inhibits the generation of lithium dendrites, constructs a homogeneous SEI layer with high mechanical strength and rich in inorganic components (such as LiF and Li3N), and improves the safety performance of the battery.

[0004] To achieve the above-mentioned purpose, the application provides an electrolyte additive, namely organic nitrate guanidine nitrate, with a chemical molecular formula of C(NH2)NO3.

[0005] In a second aspect, the application provides an electrolyte comprising a lithium salt, a solvent, a first additive and a second additive; the lithium salt is any one or more of lithium hexafluorophosphate, lithium bis-trifluoromethanesulfonimide, lithium bisfluorosulfonimide, lithium perchlorate, lithium tetrafluoroborate, lithium bisoxalate borate, lithium nitrate, lithium difluoro oxalate borate or lithium difluoro di-oxalate phosphate. Preferably, the lithium salt comprises lithium hexafluorophosphate and lithium bis-trifluoromethanesulfonimide.

[0006] The solvent is a mixed solvent of two or more carbonic acid ester solvents or ether solvents, and the solvent is selected from any one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, propyl propionate, methyl ethyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, tetrahydrofuran, 2-methyl tetrahydrofuran, 4-methyl-1,3-dioxolane, dimethoxymethane, 1,2-dimethoxyethane, 1,2-dimethoxypropane or diethylene glycol dimethyl ether. Preferably, the solvent comprises ethylene glycol dimethyl ether and 1,3-dioxolane.

[0007] Preferably, the use concentration of the first additive C(NH2)NO3 is 0.01 M-0.2 M.

[0008] The electrolyte or comprises a second additive selected from any one or more of lithium nitrate, potassium nitrate, silver nitrate, bismuth nitrate, zinc nitrate, sodium nitrate, cesium nitrate, ammonium nitrate, cerium nitrate, calcium nitrate, p-nitroaniline, bismuth subnitrate, potassium nitrite, sodium nitrite, lithium nitrite, silver nitrite, fluoroethylene carbonate, vinylene carbonate, lithium bisfluorosulfonylimide, lithium difluoro(oxalato)borate or lithium difluorophosphate. Preferably, the second additive comprises lithium nitrate, potassium nitrate and is used at a concentration of 0.01 M to 0.1 M.

[0009] In a third aspect, the present application provides a lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte; the electrolyte is the electrolyte of any one of the above technical solutions.

[0010] Preferably, the positive electrode active material is selected from any one of sulfur, lithium iron phosphate, lithium cobaltate, lithium titanate, ternary lithium nickel cobalt manganese, lithium nickel manganese acid, or lithium manganese iron phosphate.

[0011] Preferably, the negative electrode active material is selected from any one of artificial graphite, natural graphite, lithium titanate, metallic lithium, silicon-carbon composite material or silicon monoxide.

[0012] Preferably, the separator is any one or more of glass fiber, polypropylene separator or polyethylene separator.

[0013] The electrolyte additive guanidine nitrate of the present application, on the one hand, NO3 2− is preferentially reduced and decomposed on the surface of the lithium negative electrode, forming a high-quality SEI rich in Li3N and LiN x O y ; on the other hand, the bulky C(NH2)3 + group is adsorbed on the lithium surface, maintaining the lithium nucleation rate while inhibiting dendrite growth, ultimately obtaining a uniform spherical deposition morphology. The addition of C(NH2)3NO3 effectively reduces the side reactions at the SEI interface, improving the cycle performance of the battery. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 is the SEM characterization picture in Example 1.

[0015] Figure 2 is the SEM characterization picture in Example 6. DETAILED DESCRIPTION

[0016] In accordance with the embodiments of the present application, the technical solutions will now be described in detail. It should be noted that the following examples are only some exemplary embodiments of the present application, and are not all possible embodiments. Based on the content described in the specification, any person skilled in the art can think of equivalent embodiments without creative labor, which should be considered as falling within the protection scope of the claims of the present application.

[0017] Example 1: A mixed solvent of DOL and DME in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI and 0.01 M C(NH2)NO3 electrolyte additive were added to obtain an electrolyte.

[0018] The lithium-copper half-cell of the present example includes a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the positive electrode is a commercial copper foil, and the active material used for the negative electrode is metal lithium.

[0019] Battery assembly: The positive electrode, the negative electrode, the separator and the electrolyte were assembled into a battery to obtain the half-cell. The morphology was characterized by SEM, as shown in Figure 1 .

[0020] Example 2: A mixed solvent of DOL and DME in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI and 0.01 M C(NH2)NO3 electrolyte additive were added to obtain an electrolyte.

[0021] The lithium ion battery of the present example includes a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the active material used for the positive electrode is sulfur, and the active material used for the negative electrode is metal lithium.

[0022] Battery assembly: The positive electrode, the negative electrode, the separator and the electrolyte were assembled into a battery to obtain the lithium ion battery.

[0023] Example 3: A mixed solvent of DOL and DME in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI and 0.05 M C(NH2)NO3 electrolyte additive were added to obtain an electrolyte.

[0024] The lithium ion battery of the present example includes a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the active material used for the positive electrode is sulfur, and the active material used for the negative electrode is metal lithium.

[0025] Battery assembly: the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain the lithium ion battery.

[0026] Example 4: A mixed solvent of DOL and DME in a volume ratio of 1:1 is taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI and 0.1 M C(NH2)NO3 electrolyte additive are added to obtain an electrolyte.

[0027] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is sulfur, and the active material used in the negative electrode is metal lithium.

[0028] Battery assembly: the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain the lithium ion battery.

[0029] Example 5: A mixed solvent of DOL and DME in a volume ratio of 1:1 is taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI and 0.15 M C(NH2)NO3 electrolyte additive are added to obtain an electrolyte.

[0030] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is sulfur, and the active material used in the negative electrode is metal lithium.

[0031] Battery assembly: the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain the lithium ion battery.

[0032] Example 6: A mixed solvent of DOL and DME in a volume ratio of 1:1 is taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI, 0.02 M C(NH2)NO3 and 2% (mass fraction) LiNO3 electrolyte additive are added to obtain an electrolyte.

[0033] The lithium copper half-cell of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the positive electrode is a commercial copper foil, and the active material used in the negative electrode is metal lithium.

[0034] Battery assembly: the positive electrode, negative electrode, separator and electrolyte are assembled into a battery to obtain the lithium ion battery. Figure 2

[0035] ​Example 7: A mixed solvent of DOL and DME in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI, 0.1 M C(NH2)NO3 and 0.1 M LiNO3 electrolyte additives were added thereto to obtain an electrolyte.

[0036] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is sulfur, and the active material used in the negative electrode is metal lithium.

[0037] Battery assembly: the positive electrode, the negative electrode, the separator and the electrolyte were assembled into a battery to obtain the lithium ion battery.

[0038] Example 8: A mixed solvent of DOL and DME in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI, 0.1 M C(NH2)NO3 and 0.1 M KNO3 electrolyte additives were added thereto to obtain an electrolyte.

[0039] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is sulfur, and the active material used in the negative electrode is metal lithium.

[0040] Battery assembly: the positive electrode, the negative electrode, the separator and the electrolyte were assembled into a battery to obtain the lithium ion battery.

[0041] Example 9: A mixed solvent of DOL and DME in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiTFSI, 0.01 M C(NH2)NO3 and 0.1 M LiNO3 electrolyte additives were added thereto to obtain an electrolyte.

[0042] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metal lithium.

[0043] Battery assembly: the positive electrode, the negative electrode, the separator and the electrolyte were assembled into a battery to obtain the lithium ion battery.

[0044] Example 10: A mixed solvent of EC and DEC in a volume ratio of 1:1 was taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiPF6 and 0.1 M C(NH2)NO3 were added thereto to obtain an electrolyte.

[0045] The lithium ion battery of the present embodiment comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0046] Battery assembly: the positive electrode, the negative electrode, the separator and the electrolyte are assembled into a battery to obtain the lithium ion battery.

[0047] Example 11: A mixed solvent of EC, DEC and DME in a volume ratio of 1:1:1 is taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiPF6, 0.1 M C(NH2)NO3 are added to obtain an electrolyte.

[0048] The lithium ion battery of the present embodiment comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0049] Battery assembly: the positive electrode, the negative electrode, the separator and the electrolyte are assembled into a battery to obtain the lithium ion battery.

[0050] Example 12: A mixed solvent of EC, DEC and DME in a volume ratio of 1:1:1 is taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiPF6, 0.01 M C(NH2)NO3 and 0.1 M LiNO3 are added to obtain an electrolyte.

[0051] The lithium ion battery of the present embodiment comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0052] Battery assembly: the positive electrode, the negative electrode, the separator and the electrolyte are assembled into a battery to obtain the lithium ion battery.

[0053] Example 13: A mixed solvent of EC, DEC and DME in a volume ratio of 1:1:1 is taken out in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), and 1 M LiPF6, 0.01 M C(NH2)NO3 and 0.1 M KNO3 are added to obtain an electrolyte.

[0054] The lithium ion battery of the present embodiment comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the electrolyte described above; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0055] Battery assembly: Assemble the positive electrode, negative electrode, separator and electrolyte into a battery to obtain the lithium ion battery.

[0056] Example 14: Take out a mixed solvent of EC, DEC and DME in a volume ratio of 1:1:1 in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), add 1 M LiPF6, 0.1 M C(NH2)NO3 and 0.1 M KNO3 into the mixed solvent to obtain an electrolyte.

[0057] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0058] Battery assembly: Assemble the positive electrode, negative electrode, separator and electrolyte into a battery to obtain the lithium ion battery.

[0059] Example 15: Take out a mixed solvent of EC, DEC and DME in a volume ratio of 1:1:1 in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), add 1 M LiPF6, 0.1 M C(NH2)NO3 and 0.1 M NaNO3 into the mixed solvent to obtain an electrolyte.

[0060] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0061] Battery assembly: Assemble the positive electrode, negative electrode, separator and electrolyte into a battery to obtain the lithium ion battery.

[0062] Example 16: Take out a mixed solvent of EC, DEC and DME in a volume ratio of 1:1:1 in an argon-filled glove box (H2O < 0.1 ppm, O2 < 0.1 ppm), add 1 M LiPF6, 0.1 M C(NH2)NO3, 0.1 M KNO3 and 0.1 M LiNO3 into the mixed solvent to obtain an electrolyte.

[0063] The lithium ion battery of the present example comprises a positive electrode, a negative electrode, a separator and an electrolyte. The electrolyte is the above-mentioned electrolyte; the active material used in the positive electrode is LiFePO4, and the active material used in the negative electrode is metallic lithium.

[0064] Battery assembly: Assemble the positive electrode, negative electrode, separator and electrolyte into a battery to obtain the lithium ion battery.

Claims

1. An organic nitrate additive, characterized in that The organic nitrate is guanidine nitrate (C(NH2)NO3), in which NO32− can be preferentially reduced on the surface of the lithium negative electrode to form an inorganic compound-rich SEI, and then the C(NH2)3+ group undergoes characteristic adsorption on the stabilized SEI surface to work synergistically.

2. An electrolyte, characterized in that The electrolyte comprises a lithium salt, a solvent and a first electrolyte additive; the first electrolyte additive is as described in claim 1.

3. The electrolyte according to claim 2, characterized in that The lithium salt includes any one or more of lithium hexafluorophosphate, lithium bis(trifluoromethylsulfonyl imide), lithium bis(fluorosulfonyl imide), lithium perchlorate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium nitrate, lithium difluorooxalatoborate or lithium difluorobis(oxalatophosphate).

4. The electrolyte according to claim 2, characterized in that The solvent is any one or more of ethylene glycol dimethyl ether, 1,3-dioxolane, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, propyl propionate, ethyl methyl carbonate, methyl propyl carbonate, methyl formate, methyl acetate, methyl butyrate, ethyl propionate, tetrahydrofuran, 2-methyltetrahydrofuran, 4-methyl-1,3-dioxolane, dimethoxymethane, 1,2-dimethoxyethane, 1,2-dimethoxypropane or diethylene glycol dimethyl ether.

5. The electrolyte according to claim 2, characterized in that The invention comprises adding a second electrolyte additive; the second electrolyte additive is any one or more of lithium nitrate, potassium nitrate, silver nitrate, bismuth nitrate, zinc nitrate, sodium nitrate, cesium nitrate, ammonium nitrate, cerium nitrate, calcium nitrate, p-nitroaniline, bismuth subnitrate, potassium nitrite, sodium nitrite, lithium nitrite, silver nitrite, fluoroethylene carbonate, vinylene carbonate, lithium bisfluorosulfonyl imide, lithium difluoro(oxalato)borate or lithium difluorophosphate.

6. The electrolyte according to claim 2, characterized in that The solvent accounts for 72-90% by mass of the electrolyte, the sum of the first electrolyte additive and the second electrolyte additive accounts for 0.01-20% by mass of the electrolyte, and the lithium salt accounts for 8-25% by mass of the electrolyte.

7. A lithium-ion battery, characterized in that: It includes a positive electrode, a separator, an electrolyte, and a negative electrode; the positive electrode active material is selected from any one of sulfur, lithium iron phosphate, lithium cobalt oxide, lithium titanate, ternary nickel cobalt manganese lithium, lithium nickel manganese oxide, or lithium manganese iron phosphate; the separator is any one or more of glass fiber, polypropylene separator or polyethylene separator; the active material of the negative electrode is selected from any one of artificial graphite, natural graphite, lithium titanate, metallic lithium, silicon-carbon composite material or silicon oxide.

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