Thioamide-containing electrolytes for use in electrochemical cells

Abstract

Improved electrolytes for electrochemical cells are provided. The carbonate-based electrolyte can include a thioamide compound (e.g., thioacetamide (TAA), thiourea (THU), or thioformamide). The electrolyte can include a salt, a carbonate solvent, and the thioamide compound as an additive. The thioamide compound can be present, for example, at a concentration of 1 millimolar (mM) to 100 mM.

Description

[Technical Field]

[0001] The present invention relates to electrolytes containing thioamides for use in electrochemical cells. [Background technology]

[0002] Good stability and high cycling performance of lithium metal anodes are essential for the development and commercialization of high-energy-density lithium metal batteries (LMBs). Electrolyte additives, typically in amounts of 5% by weight or volume of the electrolyte, can interact with the negative and positive electrode surfaces via diffusion (e.g., physical adsorption or chemical absorption) or non-diffusion mechanisms (e.g., ion pairing, complex formation, and surface tension) to form passivation layers that enhance electrode stability during cycling (see, for example, Non-Patent Documents 1 and 2). Various organic and inorganic compounds have been investigated as electrolyte additives for LMBs, with the most common series including fluorine-containing compounds (e.g., fluoroethylene carbonate (FEC)), unsaturated carbonates (e.g., vinylene carbonate (VC)), silicon-containing compounds (e.g., tris(trimethylsilyl) phosphate (TTSP)), and nitrogen-containing compounds (e.g., lithium nitrate (LiNO)). [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Eshetu et al. Electrolyte Additives for Lithium Metal Anode and Rechargeable Lithium Metal Batteries:Progress and Perspectives, Angew.Chem.- Int.Ed, vol. 57, No.46, pp. 15002-15027, 2018, doi: 10.1002 / anie.201712702 [Non-patent document 2] Zhang, A review on electrolyte additives for lithium-ion batteries, J. Power Sources, vol. 162, no. 2, pp. 1379-1394, 2006, doi: 10.1016 / j.jpowsour.2006.07.074 [Non-patent document 3] Zhao et al., Recent advances in the research of functional electrolyte additives for lithium-ion batteries, Curr. Opin. Electrochem., vol. 6, no. 1, pp. 84-91, 2017, doi: 10.1016 / j.coelec.2017.10.012 [Non-patent document 4] Maxfield et al., Polymeric electrode coated with a reaction product or organosulfur compound, Sep. 18, 1984 [Non-Patent Document 5] Naruse et al., "Secondary nonaqueous electrolyte batteries using improved electrolyte solvents, May 06, 1997 [Non-patent document 6] Shima et al., Electrolyte solutions containing cyclic sulfate esters for secondary lithium batteries, Jul. 21, 1998 [Non-Patent Document 7] An等人,含硫和含硅化合物作为锂离子电池中基于氧化硅的阳极 / 镍钴锰酸锂811阴极的高效电解质添加剂,《科学报告》,第9卷,第1期,第14108页,2019年10月,doi: 10.1038 / s41598-019-49568-1 [Non-Patent Document 8] Li等人,硫酸乙烯酯作为成膜添加剂以改善锂离子电池石墨电极的兼容性,《离子学》,第20卷,第6期,第795 - 801页,2014年,doi: 10.1007 / s11581-013-1036-5 [Non-Patent Document 9] Ota等人,用于锂电池的碳酸丙烯酯 / 亚硫酸乙烯酯电解质体系中石墨阳极上固体电解质界面(SEI)的热解吸气相色谱 / 质谱分析,《电源杂志》,第97 - 98卷,第107 - 113页,2001年,doi: 10.1016 / s0378-7753(01)00738-8 [Non-Patent Document 10] Kamimachi等人,在电极和非水电电池的充放电循环中具有良好耐降解性的氧化还原活性聚合物,2005年7月21日 [Non-Patent Document 11] Kim et al., Cathode active material for lithium secondary battery having improved operational stability, and electrical property, May 07, 2020 [Non-Patent Document 12] Kojima et al., Secondary lithium-ion batteries with cation-conducting (thio)amide-containing polymer electrolytes, Apr. 04, 2013 [Non-Patent Document 13] He et al., Dual-enhancement on electrochemical performance with thioacetamide as an electrolyte additive for lithium-sulfur batteries, Electrochimica Acta, vol. 376, p. 138041, 2021, doi: https: / / doi.org / 10.1016 / j.electacta.2021.138041 [Non-Patent Document 14] Wang et al., Dendrite-Free Lithium Deposition via a Superfilling Mechanism for High-Performance Li-Metal Batteries, Adv. Mater., vol. 31, no. 41, pp. 1-10, 2019, doi: 10.1002 / adma.201903248 Summary of the Invention [Means for solving the problem]

[0004] Embodiments of the present invention provide novel and advantageous compounds, devices, and methods for improved battery systems (e.g., lithium (Li)-ion battery systems). Carbonate-based electrolytes can include a thioamide compound (e.g., thioacetamide (TAA), thiourea (THU), or thioformamide) and can provide improved results when used in battery systems (e.g., Li-ion battery systems), including cycle stability, interfacial resistance, and overpotential stabilization. The electrolyte can include a salt (e.g., a lithium salt such as lithium hexafluorophosphate (LiPF) or lithium tetrafluoroborate (LiBF)), a carbonate solvent (e.g., ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC)), and a thioamide compound as an additive. The thioamide compound can be present, for example, at a concentration of 1 millimolar (mM) to 100 mM.

[0005] In one embodiment, an electrolyte for an electrochemical cell can include a carbonate solvent, a salt dissolved in the carbonate solvent, and a thioamide compound dissolved in the carbonate solvent. The thioamide compound can be, for example, TAA, THU, or thioformamide. The thioamide compound can be present in the carbonate solvent at a concentration ranging from 1 mM to 100 mM (e.g., 1 mM to 50 mM, or 1 mM to 10 mM). The salt can be, for example, LiPF or LiBF. The salt can be present in the carbonate solvent at a concentration ranging from 0.5 molar (M) to 5 M (e.g., 1 M or about 1 M). The carbonate solvent can be, for example, EC, EMC, or DMC.

[0006] In a further embodiment, the electrochemical cell can include an anode, a cathode, a separator disposed between the anode and the cathode, and an electrolyte as disclosed herein disposed within the separator (e.g., impregnated and / or injected into the dry portion of the separator). The anode can be, for example, a lithium metal anode, the cathode can be, for example, a metal oxide cathode, and the electrochemical cell can be, for example, a Li-ion cell. The electrochemical cell can have stability for at least 220 cycles (e.g., at least 230 cycles, at least 240 cycles, at least 250 cycles, or at least 260 cycles) with 90% capacity retention.

[0007] In another embodiment, a method for producing an electrolyte for an electrochemical cell can include providing a carbonate solvent, dissolving a salt in the carbonate solvent, and dissolving a thioamide compound in the carbonate solvent to obtain an electrolyte. The thioamide compound can be, for example, TAA, THU, or thioformamide. The thioamide compound can be dissolved in the carbonate solvent at a concentration ranging from 1 mM to 100 mM (e.g., from 1 mM to 50 mM, or from 1 mM to 10 mM). The salt can be, for example, LiPF or LiBF. The salt can be dissolved in the carbonate solvent at a concentration ranging from 0.5 M to 5 M (e.g., 1 M or about 1 M). The carbonate solvent can be, for example, EC, EMC, or DMC. [Brief explanation of the drawings]

[0008] [Figure 1] The chemical structures of three thioamide compounds are shown: thioacetamide (TAA), thiourea (THU), and thioformamide. [Figure 2] 1 is a plot of capacity retention (percentage (%)) versus cycle number showing the cycling performance of NMC811 lithium (Li) full cells using an electrolyte containing TAA (solid line) and a control electrolyte (dashed line). [Figure 3]Figure 1 shows initial electrochemical impedance spectroscopy (EIS) Nyquist plots of Z" (ohms (Ω)) versus Z' (Ω) for NMC811 Li full cells using electrolyte with TAA (round data points) and NMC811 Li full cells using control electrolyte (square data points). [Figure 4] Figure 1 shows a plot of Z" (Ω) versus Z' (Ω) showing EIS Nyquist plots after activation and one C / 3 charge cycle for NMC811 Li full cells with electrolyte containing TAA (round data points with low Z" values) and NMC811 Li full cells with control electrolyte (square data points with high Z" values). [Figure 5] Figure 1 shows a cyclic voltammetry (CV) plot of current (milliamperes (mA)) versus voltage (volts (V)) versus Li / Li+ for an NMC811 Li full cell using an electrolyte with TAA (solid line) and an NMC811 Li full cell using a control electrolyte (dashed line). [Figure 6] 1 is a plot of % capacity retention versus cycle number showing the cycling performance of NMC811 lithium (Li) full cells using electrolytes containing THU (solid line) and control electrolytes (dashed line). [Figure 7] 1 is a plot of voltage (V) versus cycle number showing symmetric cell charge / discharge data for an electrolyte containing TAA (lower voltage values ​​at higher cycle numbers, solid line) and a control electrolyte (higher voltage values ​​at higher cycle numbers, dashed line). The current density was 4 milliamps per square centimeter (mA / cm). [Figure 8] Figure 1 is a plot of voltage (V) versus cycle number showing symmetric cell charge / discharge data for an electrolyte containing THU (lower voltage values ​​at higher cycle numbers, solid line) and a control electrolyte (higher voltage values ​​at higher cycle numbers, dashed line). The current density was 4 mA / cm. DETAILED DESCRIPTION OF THE INVENTION

[0009] Embodiments of the present invention provide novel and advantageous compounds, devices, and methods for improved battery systems (e.g., lithium (Li)-ion battery systems). Carbonate-based electrolytes can include a thioamide compound (e.g., thioacetamide (TAA), thiourea (THU), or thioformamide) and can provide improved results when used in battery systems (e.g., Li-ion battery systems), including cycle stability, interfacial resistance, and overpotential stabilization. The electrolyte can include a salt (e.g., a lithium salt such as lithium hexafluorophosphate (LiPF) or lithium tetrafluoroborate (LiBF)), a carbonate solvent (e.g., ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC)), and a thioamide compound as an additive. The thioamide compound can be present, for example, at a concentration of 1 millimolar (mM) to 100 mM.

[0010] The use of electrolyte additives is a simple and cost-effective strategy for improving the cyclability of lithium metal batteries (LMBs). Organosulfur compounds can provide high compatibility (i.e., high reduction potentials and electronegativity comparable to those of carbon) with common lithium-ion battery (LIB) electrode and electrolyte systems (see, for example, J. S., et al., "Electrochemical Properties of Organosulfur Compounds," vol. 1, no. 2, pp. 111-114, 2002, incorporated herein by reference in its entirety). Furthermore, the abundance of sulfur allows for low-cost, large-scale production of organosulfur compounds. Organosulfur compounds applicable to electrochemistry include cyclic sulfonates (e.g., 1,3-propanesulfone (PS)), linear sulfonates (e.g., propargyl methanesulfonate (PMS)), sulfates (e.g., 1,3,2-dioxathiolane-2,2-dioxide (DTD)), sulfites (e.g., ethylene sulfite (ES)), and sulfones (e.g., sulfolane (SL)). Other organosulfur compounds include lithium salts such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) and lithium-cyclo-difluoromethane-1,1-bis(sulfonyl)imide (LiDMSI).

[0011] Organosulfur additives such as PS and 1,4-butanesulfone (BS) have been introduced as electrolyte additives to stabilize polymer electrodes during cycling (see also Non-Patent Document 4, which is incorporated herein by reference in its entirety). ES was introduced as an electrolyte additive for LIBs due to its structural similarity to ethylene carbonate (EC) (see also Non-Patent Document 5, which is incorporated herein by reference in its entirety). The sulfate-based additive dioxathiolane-2,2-dioxide (DTD) has also been used (see also Non-Patent Document 6, which is incorporated herein by reference in its entirety). Many organosulfur compounds, including ES, PS, and DTD, benefit the positive electrode by forming a stable, sulfate-rich cathode-electrolyte interfacial (CEI) layer in Ni-rich NMC cathode and graphite anode cells (see also Non-Patent Document 7, which is incorporated herein by reference in its entirety). Nevertheless, the above-mentioned classes of organosulfur compounds decompose through a multistep and complex process, producing harmful by-products that degrade battery performance. Other issues include excessive gassing (e.g., DTD in 1.0 M LiPFEC / DMC) and high interfacial resistance upon extended cycling (e.g., ES in 1.0 M LiClOPC) (see also Non-Patent Document 8 and Non-Patent Document 9, both of which are incorporated herein by reference in their entireties).

[0012] Figure 1 shows the chemical structures of three thioamide compounds: TAA, THU, and thioformamide. Referring to Figure 1, the chemical structure of a thioamide contains a carbon-sulfur double bond (C=S) and can be represented by the general formula "R1-CS-NR2R3," where R1, R2, and R3 represent organic groups (see also Non-Patent Documents 10, 11, 12, 13, and 14, all of which are incorporated herein by reference in their entireties).

[0013] In one embodiment, the formulated carbonate-based electrolyte system can include at least one (e.g., exactly one) thioamide compound (e.g., TTA, THU, or thioformamide). The formulated carbonate-based electrolyte can be used with an intercalated layered metal oxide cathode (e.g., LiNi 0.8 Mn 0.1 Co 0.1 O2 (NMC811) or LiNi 0.6 Mn 0.2 Co 0.2 The present invention can be used in battery systems (e.g., lithium ion battery (LIB) systems), such as systems using O2 (NMC662)) and metal anodes (e.g., lithium metal anodes).

[0014] The electrolyte can include a salt (e.g., a lithium salt such as lithium hexafluorophosphate (LiPF) or lithium tetrafluoroborate (LiBF)), a carbonate solvent (e.g., ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC)), and a thioamide compound (e.g., TAA, THU, or thioformamide) as an additive. The thioamide compound can be present at a concentration that is, is about, is the lowest of, is the highest of, or is within any range ending at any of the following values: 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 125, 150, 175, 200, 250, or 300. For example, the thioamide compound can be present at a concentration ranging from 1 mM to 100 mM (e.g., 1 mM to 50 mM, or 1 mM to 10 mM). The purity of the thioamide compound can be any of the following values, approximately any of the following values, the lowest of any of the following values, the highest of any of the following values, or within any range ending at any of the following values ​​(all values ​​are in percent (%)): 80, 85, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 99.1, 99.2, 99.3, 99.4, 99.5, 99.6, 99.7, 99.8, 99.9, or 100. For example, the purity of the thioamide compound can be at least 99%.

[0015] Electrolytes containing thioamide compounds improve cycling stability compared to electrolytes without thioamide compounds. For example, electrolytes containing TAA can provide stability for over 260 cycles at 90% capacity retention, electrolytes containing THU can provide stability for over 230 cycles at 90% capacity retention, while electrolytes without thioamide compounds provide stability for 150 cycles at 90% capacity retention. An electrolyte without thioamide compounds (which can be referred to as a "blank" electrolyte) was identical to the electrolyte containing thioamide compounds except for the absence of thioamide compounds. The use of thioamide electrolytes containing amine and carbonyl functional groups (-NH2, -C=O) in the electrolyte can stabilize the SEI layer on the anode surface by preventing or suppressing the violent decomposition of the Li salt anions. The role of the carbonyl groups is to coordinate with Li+ ions, while the amine groups coordinate with the salt anions, thereby improving the cycling stability of the Li anode in batteries. Because the S-Li coordination bond is softer than the O-Li bond, the thioamide additive can extend the battery cycle life due to its synergistic effect compared with the amide or carbonyl additive alone. Therefore, the cycling stability of Li anodes in the presence of thioamide in the electrolyte system can be attributed to the faster and smoother coordination of Li+ ions during battery operation.

[0016] Electrolytes containing thioamide compounds are easy to use and remain stable even after storage for several weeks. When storing electrolytes for long periods (e.g., more than one week), molecular sieves can be used to remove water.

[0017] Electrolytes according to embodiments of the present invention containing a thioamide additive advantageously stabilize anodes (e.g., Li metal anodes) in batteries (e.g., Li-ion batteries), reducing dendritic and ohmic resistance growth and providing longer cycle life. The inclusion of a thioamide additive (e.g., at a concentration of 1 mM to 100 mM) in a carbonate-based electrolyte forms a stabilizing / passivating layer on the surface of the anode (e.g., Li anode) during the initial formation cycle, passivating the anode to the carbonate electrolyte and stabilizing the anode. This stabilization preserves ionic conduction pathways while maintaining a stable solid electrolyte interface, thereby extending the cycle life of the battery.

[0018] In one embodiment, a battery (e.g., a Li-ion battery or LMB) can include an anode, a cathode, a separator, and an electrolyte as disclosed herein. The separator can be, for example, a polypropylene separator, but embodiments are not limited to this. The anode can be, for example, a Li metal anode, but embodiments are not limited to this. The cathode can be, for example, a metal oxide cathode. The electrolyte can be applied to the separator (e.g., the separator can be soaked in the electrolyte for a period of time (e.g., several hours), or the electrolyte can be poured directly into the dry separator during battery assembly).

[0019] Embodiments of the present invention also provide methods for making an electrolyte containing a thioamide compound. The thioamide compound (e.g., at a concentration disclosed herein, such as 1 mM to 100 mM) can be added to a carbonate solvent (e.g., EC, EMC, or DMC). A salt (e.g., a lithium salt such as LiPF or LiBF) can be added to the carbonate solvent either before or after adding the thioamide compound. For example, a salt can be added to a solvent (e.g., at a concentration of 0.5 M to 5 M, e.g., 1 M) and dissolved, and then a thioamide compound can be added to the solvent and dissolved to form an electrolyte. A method for forming a battery can include providing an anode and a cathode and then providing an electrolyte as disclosed herein to the battery (e.g., applying the electrolyte to the battery separator). The separator can be soaked in the electrolyte for a period of time (e.g., several hours), or the electrolyte can be poured directly into a dry separator during battery assembly.

[0020] The transitional phrase "comprising" is inclusive or open-ended and does not exclude additional, unrecited elements or method steps. In contrast, the transitional phrase "consisting of" excludes elements, steps, or ingredients not specified in the claim. The phrases "consisting of" or "essentially consisting of" indicate that the claim includes embodiments that include the specified materials or steps and embodiments that do not materially affect the basic and novel characteristics of the claim. Use of the term "comprising" contemplates other embodiments that "consist of" or "consist essentially of" the recited components.

[0021] When ranges, such as dose ranges, combinations and subcombinations of ranges (e.g., subranges within the disclosed ranges), are used herein, it is intended that specific embodiments therein are expressly included. When the term "about" is used in conjunction with a numerical value herein, it is understood that the value may be within 95% to 105% of the value, i.e., the value may be + / - 5% of the stated value. For example, "about 1 kg" means 0.95 kg to 1.05 kg.

[0022] The following examples, given by way of illustration, will provide a better understanding of the embodiments of the present invention and their many advantages. The following examples illustrate some of the methods, uses, embodiments, and variations of the present invention. Of course, they should not be construed as limiting the present invention. Numerous variations and modifications can be made to the embodiments of the present invention.

[0023] Example 1 - Performance of NMC811 Li full cells with TAA NMC811 cathode (8-12 milligrams per square centimeter (mg / cm) 2 Full CR2032 coin cells containing the NMC cathode, lithium metal anode, and polypropylene separator (Celgard) were first assembled with blank electrolyte (no thioamide compound) and then separately with electrolytes containing the TAA described herein. The TAA concentration ranged from 1 mM to 10 mM in 1 molar (M) LiPF6EC / DMC. The polypropylene separator was soaked overnight in the blended electrolyte, or the electrolyte was poured directly onto the dry separator during cell assembly. The blended electrolyte was dropped onto the NMC cathode surface or lithium foil surface and allowed to react / set before final assembly. The coin cells were assembled using a crimping pressure of 70 pounds per square inch (psi) to 90 psi.

[0024] The cells were initially placed in a static state, then activated at a slow rate, followed by continuous cycling at a higher rate (e.g., C / 3 charge, 1C discharge). Referring to Figure 2, the cells using the TAA-blended electrolyte were stable for 230 cycles with 90% capacity retention, compared to only 150 cycles for the control (or blank, i.e., without the thioamide compound) electrolyte. Referring to Figure 2, initial electrochemical impedance spectroscopy (EIS) measurements of fresh full cells showed an interfacial resistance of 80 ohms (Ω) for both the blank and TAA electrolytes. Referring to Figure 4, EIS measurements after the activation cycle and one high-charge-rate cycle showed increased resistance for the blank electrolyte cell compared to the TAA-blended electrolyte cell. Referring to Figure 5, cyclic voltammetry scans of full cells using the blank and TAA electrolytes showed a peak shift in the TAA-blended electrolyte cell, indicating lower overpotential stabilization compared to the control.

[0025] Example 2 - Performance of NMC811 Li full cell with THU Example 1 was repeated, except that the THU-containing electrolyte described herein was used instead of the TAA-containing electrolyte. The THU concentration was 1 mM to 10 mM TAA in 1 M LiPF6EC / DMC. The cells were initially placed in a static state, then slowly activated, followed by continuous cycling at a higher rate (e.g., C / 3 charge, 1 C discharge). Figure 6 shows that the THU-blended electrolyte cell exhibited high cycling stability, achieving 230 cycles with 90% capacity retention compared to the beginning of life (BOL) of the cell. In contrast, the control cell achieved only 150 cycles with 90% capacity retention.

[0026] Example 3 - Lithium Metal Symmetric Cell with TAA Symmetrical Li-Li electrodes were assembled from two lithium foils separated by a polypropylene separator (Celgard) in a CR2032 coin cell. The separator was soaked in the TAA-blended electrolyte (applied in Example 1) before assembly. After allowing the cell to rest, it was charged at different rates (e.g., 1.0 milliamps per square centimeter (mA / cm)). 2 ), 2.0mA / cm 2 , 4.0mA / cm 2 ) cycled at 1000 kJ / s. Referring to Figure 7, the charge / discharge data for the blank and TAA-blended electrolytes show a higher initial overpotential for the TAA-blended electrolyte. Within 10 cycles, the TAA cell stabilized below 50 millivolts (mV) and remained stable for 100 cycles. Meanwhile, for the cell using the blank electrolyte, the control cell voltage showed a continuous increase and quickly exceeded 200 mV, indicating a high growth in interfacial resistance. This symmetric cell test indicates that the lithium anode interface is more stable in the TAA-blended cell compared to the control cell using the blank electrolyte.

[0027] Example 4 - Lithium Metal Anode Symmetric Cell Using THU Example 3 was repeated, except that the electrolyte of Example 2 (containing THU) was used instead of the electrolyte containing TAA (from Example 1). The separator was soaked in the THU-blended electrolyte before assembly. After allowing the cell to rest, it was tested at different rates (e.g., 1.0 mA / cm). 2 , 2.0mA / cm 2 , 4.0mA / cm 2) were cycled. Referring to Figure 8, the charge / discharge data for the blank and THU-blended electrolytes show a higher initial overpotential for the THU-blended electrolyte. The THU cell started with a higher overpotential voltage compared to the control cell, but stabilized within the first 10 cycles. The THU cell stabilized below 30 mV after 50 cycles and remained stable for 100 cycles, while the control cell exhibited a stable voltage of 60 mV until 40 cycles, after which the voltage continuously increased and rapidly exceeded 200 mV. This symmetric cell test indicates that the lithium anode interface is more stable in the THU-blended cell compared to the control cell using the blank electrolyte.

[0028] It is to be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof may be suggested to those skilled in the art and are within the spirit and scope of the present application.

[0029] All patents, patent applications, provisional applications, and publications mentioned or cited herein are incorporated by reference in their entirety, including all figures and tables, to the extent not inconsistent with the explicit teachings of this specification.

Claims

1. a carbonate solvent; a salt dissolved in the carbonate solvent; and a thioamide compound dissolved in said carbonate solvent.

2. 2. The electrolyte of claim 1, wherein the thioamide compound is thioacetamide (TAA), thiourea (THU), or thioformamide.

3. The electrolyte of claim 2 , wherein the thioamide compound is TAA or THU.

4. 4. The electrolyte of claim 1, wherein the thioamide compound is present in the carbonate solvent at a concentration ranging from 1 millimolar (mM) to 100 mM.

5. 5. The electrolyte of claim 4, wherein the thioamide compound is present in the carbonate solvent at a concentration ranging from 1 mM to 50 mM.

6. The salt is lithium hexafluorophosphate (LiPF ６ ) or lithium tetrafluoroborate (LiBF ４ 6. The electrolyte according to claim 1, wherein

7. 7. The electrolyte of claim 1, wherein the salt is present in the carbonate solvent at a concentration ranging from 0.5 molar (M) to 5M.

8. 8. The electrolyte of claim 1, wherein the carbonate solvent is ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC).

9. an anode; a cathode; a separator disposed between the anode and the cathode; and an electrolyte according to any one of claims 1 to 8 disposed within said separator.

10. the anode is a lithium metal anode; the cathode is a metal oxide cathode; 10. The electrochemical cell of claim 9, wherein the electrochemical cell is a lithium ion cell.

11. providing a carbonate solvent; Dissolving a salt in the carbonate solvent; a method for preparing an electrolyte for an electrochemical cell, comprising dissolving a thioamide compound in said carbonate solvent to obtain an electrolyte.

12. 12. The method of claim 11, wherein the thioamide compound is thioacetamide (TAA), thiourea (THU), or thioformamide.

13. The method of claim 12, wherein the thioamide compound is TAA or THU.

14. The method of any one of claims 11 to 13, wherein the thioamide compound is dissolved in the carbonate solvent at a concentration ranging from 1 millimolar (mM) to 100 mM.

15. 15. The method of claim 14, wherein the thioamide compound is dissolved in the carbonate solvent at a concentration ranging from 1 mM to 50 mM.

16. The salt is lithium hexafluorophosphate (LiPF ６ ) or lithium tetrafluoroborate (LiBF ４ The method according to any one of claims 11 to 15, wherein

17. 17. The method of any of claims 11 to 16, wherein the salt is dissolved in the carbonate solvent at a concentration ranging from 0.5 molar (M) to 5M.

18. 18. The method of any one of claims 11 to 17, wherein the carbonate solvent is ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC).

19. a carbonate solvent; a salt dissolved in the carbonate solvent; a thioamide compound dissolved in the carbonate solvent, the thioamide compound is thioacetamide (TAA) or thiourea (THU); the thioamide compound is present in the carbonate solvent at a concentration of 1 millimolar (mM) to 50 mM; The salt is lithium hexafluorophosphate (LiPF ６ ) or lithium tetrafluoroborate (LiBF ４ ) and the salt is present in the carbonate solvent at a concentration ranging from 0.5 molar (M) to 5 M; 1. An electrolyte for an electrochemical cell, wherein the carbonate solvent is ethylene carbonate (EC), ethyl methyl carbonate (EMC), or dimethyl carbonate (DMC).

20. a lithium metal anode; a metal oxide cathode; a polypropylene separator disposed between the anode and the cathode; and the electrolyte of claim 19 disposed within the polypropylene separator. Lithium-ion batteries are electrochemical batteries.

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