Electrode material and process for preparing them

Abstract

To provide an electrode material and a process for preparing them.SOLUTION: The present invention relates to an electrode material containing an indigoid compound, that is, e.g., an indigo blue or its inductor with particles of an electrochemical active material scattered in, e.g., a binder. In addition, the present invention relates to a process for preparing the electrode material, an electrode containing the electrode material, an electrochemical cell, and the use of them. According to an embodiment, a chemical compound is the indigo blue. In another embodiment, the chemical compound of a formula I is leuco-indigo or its salt. In another embodiment, the chemical compound is selected from the indigo, an indigo carmine, an iso-indigo, an indigo purpurin, and an indolinedione.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Related Applications This application claims priority to U.S. Provisional Application No. 62 / 459,309, filed on February 15, 2017, the content of which is hereby incorporated by reference in its entirety for all purposes.

[0002] Technical Field The technical field generally relates to electrode materials and processes for their preparation, such as electrode materials including electrochemically active materials and organic additives. This application also relates to the use of electrode materials for the preparation of electrodes and their use in electrochemical cells.

Background Art

[0003] Background Indigo blue is a pigment extracted from plants that has originally been used as a dye for centuries. The molecule itself has been studied for various aspects including its amphoteric organic semiconductor properties. Indigo blue dye, which is essentially insoluble in water, has also been reduced to its colorless and soluble leuco - indigo form (indigo white). This redox property has been further studied recently in electrochemistry. For example, indigocarmine, an indigo blue analogue, has been tested as a purely organic cathode active material in rechargeable batteries (Yao M. et al., Scientific Reports, Vol. 4, 3650, pp. 1 - 6).

Prior Art Documents

Non - Patent Documents

[0004]

Non - Patent Document 1

Summary of the Invention

Means for Solving the Problems

[0005] Summary In one aspect, the present application relates to particles of an electrochemically active material and an indigoid compound, such as those of formulas I-IV:

Chem.

[0006] In one embodiment, the compound is of formula I. In another embodiment, the compound is of formula II. In a further embodiment, the compound is of formula III. For example, R 2 and R 6 are the same and are selected from halogen (e.g., F), optionally halogenated alkyl, -CN, and -SO2OM 2 , e.g., -CN. In another example, R 3 and R 7 are the same and are selected from halogen (e.g., F), optionally halogenated alkyl, -CN, and -SO2OM 2 , e.g., -CN. In one embodiment, each of R 1 ~R 8 is a hydrogen atom.

[0007] In another embodiment, the compound is of formula IV, e.g., R 2 ​is halogen (e.g., F), optionally halogenated alkyl, -CN, and -SO2OM 2 selected from, for example, R 2 is -CN. In another embodiment, R 1 ~R 4 each is a hydrogen atom.

[0008] In one embodiment, the compound is as follows:

Chemical formula

Chemical formula

[0009] In one embodiment, the compound is indigo blue. In another embodiment, the compound of formula I is leuco - indigo or a salt thereof. In another embodiment, the compound is selected from indigo, indigocarmine, isoindigo, indigopurpurin, and indolin dione. In yet another embodiment, the compound is compound 6. In a further embodiment, the compound is compound 7. In another embodiment, the compound is selected from compounds 8 - 10. In a further embodiment, the compound is selected from compounds 1, 8, 11, 12, and 14.

[0010] In one embodiment, the electrode material further comprises particles of an anode electrochemically active material. In different embodiments, the electrode material further comprises particles of a cathode electrochemically active material.

[0011] In one embodiment, the electrochemically active material comprises a material selected from the group consisting of titanate, lithium titanate, lithium metal phosphate, vanadium oxide, or lithium metal oxide. For example, the electrochemically active material is TiO2, Li2TiO3, Li4Ti5O 12 , H2Ti5O 11and H2Ti4O9, or a combination thereof, LiM’PO4 [where M’ is Fe, Ni, Mn, Co, or a combination thereof], LiV3O8, V2O5, LiMn2O4, LiM”O2 [where M” is Mn, Co, Ni, or a combination thereof], Li(NiM’’’)O2 [where M’’’ is Mn, Co, Al, Fe, Cr, Ti or Zr], and combinations thereof. Each of the above active materials may be doped with a compatible element as necessary.

[0012] For example, the electrochemically active material is selected from titanates and lithium titanate. According to another example, the electrochemically active material is of the formula LiM’PO4 [where M’ is Fe, Ni, Mn, Co], and optionally, a compatible element, for example, an element selected from Mg, Al, B, Ti, V, Cr, Cu, Zn, Mo, Sn, Ca, Sr and W, or a combination thereof, for example, the element Mg is doped. For example, the electrochemically active material is LiFePO4 or LiMn x Fe 1-x PO4 [where 0 < x < 1], and is optionally doped with a compatible element, for example, an element selected from Co, Ni, Mg, Al, B, Ti, V, Cr, Cu, Zn, Mo, Sn, Ca, Sr and W, or a combination thereof, for example, magnesium is doped as necessary.

[0013] In a further embodiment, the electrochemically active material is LiM”O2 [where M” is Mn, Co, Ni, or a combination thereof]. For example, the electrochemically active material is LiNi w Mn y Co z O2 [where w + y + z = 1].

[0014] According to a further embodiment, the particles are further coated with a conductive agent. In a further embodiment, the electrode material further comprises a conductive agent. In yet another embodiment , the electrode material further comprises a binder, for example, a water-soluble binder or a non-aqueous polymer binder (e.g., a fluorinated polymer binder, e.g., PVdF or PTFE). For example, the binder includes a cellulose-derived binder and / or a water-soluble binder. In a further embodiment, the compound is present in the electrode material at a concentration of 0.1 wt% to 5 wt%, or a concentration of 0.1 wt% to 2 wt%.

[0015] According to another aspect, the present application relates to a process for manufacturing an electrode comprising the electrode material as defined herein, the following steps: a) mixing a compound, particles of an electrochemically active material, and a binder in a solvent (e.g., an aqueous or non-aqueous solvent) in any order to obtain a slurry; b) casting the slurry obtained in step (a) onto a substrate (e.g., a current collector or a separator); and c) drying the cast slurry is included.

[0016] In one embodiment, the substrate is a current collector made of aluminum or an alloy having aluminum as a main component. In another embodiment, the substrate is a conductive polymer.

[0017] According to a further aspect, the present application relates to an electrode comprising the electrode material as defined herein on a current collector, or an electrode manufactured by the process as defined herein. For example, the current collector is aluminum or an alloy having aluminum as a main component, or the current collector is a conductive polymer.

[0018] According to yet a further aspect, the present application relates to an electrochemical cell comprising the electrode, electrolyte, and counter electrode (an electrode of opposite electrochemical activity) as defined herein. For example, the electrode is a positive electrode, and the negative electrode is metallic lithium, a lithium alloy (e.g., Li-Na, Li-Mg, and Li-Zn, etc.), Si, SiO x , graphite, and a carbon mixture (graphite - SiO x, graphite-Si, carbon-Si, carbon-SiO x ) and includes an electrochemically active material selected therefrom. In another example, the negative electrode includes lithium titanate (e.g., Li4Ti5O 12 ) as the electrochemically active material.

[0019] In a further aspect, the electrochemical power generation device and the electrochemical storage battery include the electrochemical cell or the electrode material defined herein.

[0020] According to a further aspect, the present application further relates to the use of the present electrochemical cell and electrode, for example, in an electric vehicle or a hybrid vehicle, or in a ubiquitous IT device, and, for example, in a mobile device, such as a mobile phone, a camera, a tablet or a laptop, or as a supercapacitor in an electric vehicle or a hybrid vehicle, or in renewable energy storage.

[0021] Other features and advantages of the present technology will be better understood by reading the following description of the present specification with reference to the accompanying drawings.

Brief Description of the Drawings

[0022]

Figure 1

[0023]

Figure 2

[0024]

Figure 3

[0025]

Figure 4

[0026]

Figure 5

[0027]

Figure 6

[0028]

Figure 7

[0029]

Figure 8

[0030]

Figure 9

[0031]

Figure 10

[0032]

Figure 11

[0033]

Figure 12

[0034]

Figure 13

[0035]

Figure 14

[0036]

Figure 15

[0037]

Figure 16

[0038]

Figure 17

[0039]

Figure 18

[0040]

Figure 19

[0041]

Figure 20

[0042]

Figure 21

[0043]

Figure 22

[0044]

Figure 23

[0045]

Figure 24

[0046]

Figure 25

[0047]

Figure 26

Embodiments for Carrying Out the Invention

[0048] Detailed Description This application relates to a process for the preparation of an electrode material containing indigo blue or a derivative thereof, or a reduced form of the indigo blue or derivative, or a salt thereof, and to an electrode manufactured by such a process.

[0049] For example, the organic additive of this application is Li + , Na + , K +It can act together with an electrolyte containing. Indigo derivatives such as the indigo derivatives used herein can store and release sodium and lithium ions during the redox reaction. Organic molecules generally have weak van der Waals or π-π type interactions, while inorganic molecules possess strong interactions such as 3D electrostatic interactions. Due to the difference in properties, organic molecules are more flexible than inorganic molecules, thereby promoting the electrochemical storage of larger charge carriers such as Na + ions. Moreover, the physicochemical properties of organic molecules can be more easily adjusted.

[0050] For example, this specification relates to the use of organic molecules as additives for electrode materials. For example, the organic molecule is an indigoid compound, i.e., indigo blue or its derivative, the leuco-indigo form or a salt, i.e., of formula I, II or III: [Chemical formula] [wherein, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 , and R 8 are each independently selected from a hydrogen atom, a halogen (e.g., F), an optionally halogenated alkyl, cycloalkyl, or aryl group, -CN, -NO2, -SO2OM 2 , -OP(O)(OM 2 )2, -P(O)(OM 2 )2, or -C(O)OM 2 , where M 2 is a cation of an alkali or alkaline earth metal, or is independently selected from -OC(O)alkyl, -SO2NH2, -SO2NHalkyl, or -SO2N(alkyl)2 groups; X is, in each occurrence independently, selected from O, S, NH, NR 9 , and PH, where R 9is selected from natural or synthetic carbohydrates and protecting groups such as amine protecting groups such as trifluoroacetamide, t-butyloxycarbonyl (Boc), benzyloxycarbonyl (Cbz), 9-fluorenylmethyloxycarbonyl (Fmoc), and benzyl (Bn), etc.; i. a, c and e are single bonds, b and d are double bonds, M 1 is H or a cation of an alkali or alkaline earth metal, such that M 1 binds to form a salt with the negatively charged oxygen atom (e.g., M 1 is Li + Na + K + Ca 2+ or Mg 2+ ), where the ratio of the cation to the rest of the compound of formula I provides electrical neutrality (e.g., M 1 is Li + or (Mg 2+ ) 1 / 2 ); or, ii. a, c and e are double bonds, b and d are single bonds, and M 1 is absent] The compound of, or its oxime (i.e., in formula I, II or III, =OM 1 is replaced by =NOH), its geometric isomers (e.g., cis or trans), or its carbohydrate (monosaccharide or disaccharide, oligosaccharide and polysaccharide, e.g., β-D-glucose or cellulose) complex or conjugate.

[0051] In one embodiment, when c is a double bond, this double bond may have a cis or trans geometric arrangement. In one embodiment, the c double bond is in a trans geometric arrangement. In another embodiment, X is NH. In a further embodiment, R 1 is the same as R 5 and / or R 2 is the same as R 6 and / or R 3 is the same as R 7 and / or R4 is the same as R 8 In another embodiment, R 1 and R 5 are both hydrogen, and / or R 2 and R 6 are both hydrogen atoms.

[0052] In one embodiment, at least one of R 1 ~R 8 is selected from fluorine, cyano and trifluoromethyl. In another embodiment, R 1 , R 4 , R 5 and R 8 are each a hydrogen atom, and R 2 , R 3 , R 6 and R 7 are as defined above. In another embodiment, R 1 , R 4 , R 5 and R 8 are each a hydrogen atom, and R 2 , R 3 , R 6 and R 7 are independently selected from fluorine, cyano and trifluoromethyl.

[0053] In a further embodiment, M 1 is present and is selected from Li, Na and K.

[0054] The indigo blue or derivative defined above (where a, c and e are double bonds) can also be converted, for example by alkaline reduction, to its reduced form (where b and d are double bonds). For example, the reduced form of indigo blue is called leuco-indigo or indigo white and can be in salt form.

[0055] In another example, the compound is a precursor of indigo blue, such as indoxyl sugar or its derivative, reduced form or salt, of formula IV:

Chemical formula

[0056] Analogues of the compounds of formula IV in which the sugar is replaced by a hydrogen atom are also contemplated.

[0057] In one embodiment, the compounds used herein are sugar or polysaccharide (e.g., cellulose) complexes or conjugates of the compounds of formula I, II or III.

[0058] In one example, the compound is of the formula:

Chemical formula

Chemical formula

[0059] According to some examples, the compound is indigo blue, or a derivative thereof having substituents on one or both of the aromatic rings. For example, one or more sulfonate groups (e.g., indigocarmine), one or more chlorine or bromine atoms (e.g., Tyrian purple, Ciba blue) or one or more nitrile groups. Other derivatives include replacement of the amine group by a sulfur atom in the ring, i.e., in this case X is S (e.g., thioindigo). In another example, the compound is indigocarmine. In yet another example , the compound is isatin. Another example of the compound is indigo purpurine. Another example of the indigoid compound is indolin dione.

[0060] Some of the compounds described in this specification can be obtained from commercial sources or can be prepared using known techniques such as those described in Tanoue et al., Dyes and Pigments, 62, 2004, 101 -105; Klimovich I.V., J. Mat. Chem., 2014, 2, 7621-7631; Horn, R.H. et al., Notes. Journal of the Chemical Society (Resumed), 1 950, 2900-2908; Voss, G. and H. Gerlach, Chemische Berichte , 1989, 122(6), 1199-1201; Baltac, T. et al., Revista de Chimie, 2012, 63(6), 618-620; Bailey, J.E. and J. Travis, Dyes and Pigments, 1985, 6(2), 135-154; Leclerc, S. et al., J. Biol. Chem., 2001, 276(1), 251-260; and Karapetyan G. et al., Chem, Med. Chem., 2011, 6, 25-37, the entire contents of which are hereby incorporated by reference for all purposes.

[0061] According to another aspect, the present application relates to an electrode material comprising a compound as defined herein as an additive. For example, the compound is present in the electrode material at a concentration of 0.1 wt% to 5 wt% or at a concentration of 0.1 wt% to 2 wt%. In one embodiment, the electrode is suitable for use in an electrochemical cell, such as a lithium or lithium ion battery. In a further embodiment, the electrode is suitable for use in a redox type supercapacitor.

[0062] In another example, the electrode material includes the compounds defined herein and particles of an electrochemically active material. In another embodiment, the electrode material includes the compounds defined herein and particles of an electrochemically active material dispersed in a binder. For example, the present invention relates to an electrode comprising an electrode material defined herein, coated on a support film, such as a current collector.

[0063] In one embodiment, the electrode is, for example, the cathode of a lithium-ion battery. The present compound can contribute as a capacity storage, as an electron conductive agent, as an ion diffusing agent, and / or as an overcharge protector. For example, the presence of the compounds described herein can result in an increase in battery capacity and / or a reduction in internal resistance, for example, when operated at low temperatures.

[0064] Similarly, when the electrode is an anode, such as the anode of a lithium-ion battery, the present compound can contribute as an overcharge protector and / or by reducing the internal resistance, for example, at room temperature and below, by increasing the electron conductivity and / or ion diffusion.

[0065] For example, the compounds defined herein can be used to improve the ion and / or electron conductivity in an electrochemical cell, even if used as an additive in the anode or cathode, or both, when operating at low temperatures, such as temperatures below room temperature, or ≤ 25 °C, or ≤ 15 °C, or ≤ 10 °C, or ≤ 0 °C, or ≤ -10 °C. For example, the electrochemical cell is operated at a temperature between -40 °C and 25 °C.

[0066] Examples of the electrochemically active material particles include inorganic particles such as metal oxides and complex oxides, and carbon particles such as graphite. Examples of electrochemically active materials include, but are not limited to, titanates and lithium titanates (e.g., TiO2, Li2TiO3, Li4Ti5O 12 , H2Ti5O 11, H2Ti4O9, or a combination thereof), lithium, and metal phosphate (e.g., LiM’PO4 [where M’ is Fe, Ni, Mn, Co, or a combination thereof]), vanadium oxide (e.g., LiV3O8, V2O5, LiV2O5, etc.), and other lithium and metal oxides, such as LiMn2O4, LiM”O2 (M” is Mn, Co, Ni or a combination thereof), Li(NiM’’’)O2 (M’’’ is Mn, Co, Al, Fe, Cr, Ti, Zr, etc., or a combination thereof), or a combination thereof, or any of the above substances further containing a compatible doping element selected from Groups 2 - 15 of the periodic table. For example, the active material is selected from lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium titanate (LTO), graphite, and lithium nickel manganese cobalt oxide (NMC).

[0067] According to another example, the electrochemically active material is of the formula LiM’PO4 [where M’ is Fe, Ni, Mn, Co or a combination thereof], and optionally, a compatible element is doped, for example, optionally, an element selected from Mg, Al, B, Ti, V, Cr, Cu, Zn, Mo, Sn, Ca, Sr and W, or a combination thereof is doped. For example, the electrochemically active material is LiFePO4 or LiMn x Fe 1-x PO4 [where 0 < x < 1], and optionally, a compatible element is doped, for example, optionally, an element selected from Co, Ni, Mg, Al, B, Ti, V, Cr, Cu, Zn, Mo, Sn, Ca, Sr and W, or a combination thereof is doped, for example, optionally, magnesium is doped. Examples of the electrochemically active material also include compounds of the formula LiM”O2 [where M” is Mn, Co, Ni or a combination thereof]. For example, the electrochemically active material is LiNi w Mn y Co z O2 [where w + y + z = 1].

[0068] The electrochemically active material particles are either newly formed or from a commercial source. They may be in the form of microparticles or nanoparticles and may further include a carbon coating.

[0069] The electrode material includes, as needed, additional components such as a conductive material, inorganic particles, glass or ceramic particles, and salts (e.g., lithium salts). Examples of conductive materials include carbon black, Ketjen (trademark) black, acetylene black, graphite, graphene, carbon fiber, nanofibers (e.g., VGCF) or nanotubes, or combinations thereof.

[0070] In one embodiment, the electrode further includes at least one binder. Examples of binders include water-soluble binders such as SBR (styrene-butadiene rubber), NBR (butadiene-acrylonitrile rubber), HNBR (hydrogenated NBR), CHR (epichlorohydrin rubber), and ACM (acrylate rubber), etc., as well as cellulose-based binders (e.g., carboxyalkyl cellulose, hydroxyalkyl cellulose, and combinations), or any combination of two or more of these. For example, carboxyalkyl cellulose can be carboxymethyl cellulose (CMC) or carboxyethyl cellulose. Hydroxypropyl cellulose is an example of hydroxyalkyl cellulose.

[0071] Other examples of binders include fluorine-containing polymer binders such as PVDF and PTFE, and ion-conductive polymer binders such as block copolymers consisting of at least one lithium ion solvation segment and at least one crosslinkable segment.

[0072] In one embodiment, the binder includes a water-soluble binder and a cellulose-based binder, for example, a combination of SBR and CMC.

[0073] This application also relates to the preparation of an electrode comprising an electrode material as defined herein. In one example, the particles of the compounds and electrochemically active materials defined herein are mixed with a binder and applied onto a substrate film (e.g., a current collector) as a slurry in a compatible solvent that can be selected, for example, also based on the binder used. For example, water can be used to prepare the slurry with a water-soluble binder and a cellulose-based binder. In another example, a non-aqueous solvent (e.g., NMP) can be used to prepare the slurry with a polymer binder (e.g., a fluorine-containing polymer binder). Further additives, such as conductive substances, may also be added to the slurry. The solvent, if present, is removed after coating the mixture or slurry. The binder is as defined above and is selected considering the compatibility with the electrochemically active material, additives, current collector, electrolyte, and other parts that can come into contact in an electrochemical cell. The slurry can be continuously applied onto the substrate film by various methods, such as comma bar coating, doctor blade coating, or slot die casting.

[0074] The slurry can be continuously applied onto the substrate film by various methods, such as comma bar coating, doctor blade coating, or slot die casting.

[0075] The electrode produced by this process is for use in the assembly of an electrochemical cell that further includes an electrolyte and a counter electrode. The material constituting the counter electrode is selected as a function of the electrochemically active material used in the electrode (e.g., electrode / counter electrode: LFP / LTO, LFP / Li, LFP / graphite, NMC / graphite, NMC / LTO, etc.). For example, the electrode is a positive electrode and the counter electrode is a negative electrode, and includes an electrochemically active material selected from metallic lithium, lithium alloys (e.g., Li-Na, Li-Mg, and Li-Zn, etc.), Si, SiO x , graphite, and carbon mixtures (graphite-SiO x , graphite-Si, carbon-Si, carbon-SiO x ). In another example, the negative electrode includes lithium titanate (e.g., Li4Ti5O 12 ) as the electrochemically active material.

[0076] The electrolyte may be a liquid, gel or solid polymer electrolyte, and in the case of a lithium or lithium-ion battery, it contains a lithium salt and / or is lithium-ion conductive. For example, the electrodes described herein can be used in a capacitor or supercapacitor, or in a battery, such as a lithium battery or lithium-ion battery.

Examples

[0077] The following non-limiting examples are illustrative embodiments and should not be construed as limiting the scope of the present application. These examples will be better understood with reference to the accompanying drawings.

[0078] Example 1: Chemical Synthesis a) Preparation of 5,5’-difluoroindigo (Compound 3) The procedure used here is based on the method of Tanoue et al. described above. Step 1: Preparation of 5-fluoro-3-iodoindole

Chemical formula

[0079] Step 2: Preparation of 3-acetoxy-5-fluoroindole

Chemical formula

[0080] Step 3: Preparation of 5,5'-difluoroindigo

Chemical formula

[0081] This method was also used for the preparation of Compounds 4, 5, 6 and 7 using the corresponding indole as starting material. Other compounds used may be commercially available.

[0082] b) General preparation of indigo derivatives The procedure used here is based on the methods of Klimovitch, Horn et al., and Voss and Gerlach described above. General Scheme 1:

Chemical formula

[0083] General method: Nitrobenzaldehyde (3.2×10 in 15 mL methanol-2 The derivative (1 mol) and nitromethane (1.1 equivalents) were slowly treated at 0 °C with a solution of sodium methoxide (prepared from sodium (1.2 equivalents) and methanol (10 mL)). After 12 hours at 0 °C Subsequently, the yellow crystalline sodium salt of 2-nitro-1-o-nitrophenylethyl alcohol was collected and washed with ether. This salt was dissolved in water, 15 mL of sodium hydroxide solution (2N) was added, and then sodium dithionite (1.1 equivalents) was added slowly with stirring. A thick precipitate of indigo formed immediately, which was collected and purified by vacuum sublimation.

[0084] Examples of compounds prepared using this procedure: Compound 3: R’: H R”: F Compound 4: R’: F R”: H Compound 5: R’: CF3 R”: H Compound 6: R’: CN R”: H Compound 7: R’: H R”: CN

[0085] c) Preparation of sulfoindigo The procedure used below is based on the method of Batlach et al. described above.

Chemical formula

[0086] d) Preparation of trisulfoindigo The following procedure is based on the method of Bailey and Travis described above.

Chemical formula

[0087] Example 2: Preparation of an exemplary electrochemical cell a) Cathode composition: The compositions of the cathodes prepared according to (c) below and used as reference or test indigoid-containing cathodes are listed in Table 1 below. [Table 1]

[0088] b) Composition of the prepared cells: The components of the cells tested are summarized in Table 2 below. Each cell is prepared as a 2032-size coin cell. The separators identified in the table are impregnated with a liquid electrolyte consisting of 1 mol / kg LiPF6 in PC / EMC (4 / 6) or PC / EMC / DMC (4 / 3 / 3). [Table 2]

[0089] c) Method for the preparation of the electrodes (weight ratios refer to Table 1 above): LFP + PVDF When indigoids (a: indigo, b: indigo carmine, and c: isoindigo, see Table 1) are present, a hybrid cathode paste was prepared by mechanically mixing (Thinky Mixer SR-500) the active material, acetylene black (Denka HS-100L), and PVdF (1300 g / mol) in NMP. The resulting viscous slurry was uniformly cast onto aluminum foil functioning as a current collector by the doctor blade method, dried at 120 °C under vacuum, roll-pressed to 59 μm with a Rolling Machine (MSK-2150), and an electrode active layer density of 8 mg / cm was achieved. The electrodes were further dried at 150 °C under vacuum before use. When indigoids are present, LFP (LCP 420B), acetylene black (Denka HS-100L), SBR (BM400B), and CMC (BSH-6) were mechanically mixed (Thinky Mixer SR-500) in water to prepare a hybrid cathode paste. The resulting viscous slurry was uniformly cast onto aluminum foil functioning as a current collector by the doctor blade method, dried at 80 °C under vacuum, roll-pressed to 59 μm with a Rolling Machine (MSK-2150), and an electrode active layer loading of 8 mg / cm 2 and a bulk density of 1.8 mg / cm

[0090] LFP+SBR-CMC were achieved. The electrodes were further dried at 150 °C under vacuum before use. 2 When indigoids are present, LTO, SBR, and CMC were mechanically mixed (Thinky Mixer SR-500) in water to prepare a hybrid cathode paste. The resulting viscous slurry was uniformly cast onto aluminum foil functioning as a current collector by the doctor blade method, dried at 80 °C under vacuum, roll-pressed to 59 μm with a Rolling Machine (MSK-2150), and an electrode active layer loading of 8 mg / cm 3 and a bulk density of 1.8 mg / cm

[0091] LTO+SBR-CMC A hybrid cathode paste was prepared by mechanically mixing LTO (T30-D8), acetylene black (Denka HS-100L), SBR (BM400B), and CMC (BSH-6) in water using a Thinky Mixer SR-500. The resulting viscous slurry was cast uniformly onto aluminum foil that functions as a current collector by the doctor blade method, dried at 80 °C under vacuum, roll-pressed to 72 μm using a Rolling Machine (MSK-2150), and achieved an electrode active layer loading of 10 mg / cm 2 and a bulk density of 1.8 mg / cm 3 . The electrodes were further dried at 150 °C under vacuum before use.

[0092] LMFP + PVDF When indigoide, active material, acetylene black (Denka HS-100L), carbon fiber (VGCF-SDH-HC), and PVdF (1300 g / mol) are present, a hybrid cathode paste was prepared by mechanically mixing them in NMP using a Thinky Mixer SR-500. The resulting viscous slurry was cast uniformly onto aluminum foil that functions as a current collector by the doctor blade method, dried at 80 °C under vacuum, roll-pressed to 63 μm using a Rolling Machine (MSK-2150), and achieved an electrode active layer density of 8.5 mg / cm 2 . The electrodes were further dried at 150 °C under vacuum before use.

[0093] LMFP + SBR-CMC When indigoid, active material, acetylene black (Denka HS-100L), carbon fiber (VGCF-SDH-HC), SBR (BM400B), and CMC (BSH-6) were present, a hybrid cathode paste was prepared by mechanically mixing (Thinky Mixer SR-500) them in water. The resulting viscous slurry was uniformly cast onto aluminum foil that functions as a current collector by the doctor blade method, dried at 80 °C under vacuum, roll-pressed to 63 μm with a Rolling Machine (MSK-2150), and achieved an electrode active layer loading of 8.5 mg / cm 2 . The electrodes were further dried at 150 °C under vacuum before use.

[0094] NMC + PVDF When indigoid, active material, acetylene black (Denka HS-100L), and PVdF (1300 g / mol) were present, a hybrid cathode paste was prepared by mechanically mixing (Thinky Mixer SR-500) them in NMP. The resulting viscous slurry was uniformly cast onto aluminum foil that functions as a current collector by the doctor blade method , dried at 80 °C under vacuum, roll-pressed to 41 μm with a Rolling Machine (MSK-2150), and achieved an electrode active layer density of 7.5 mg / cm 2 . The electrodes were further dried at 125 °C under vacuum before use.

[0095] NMC + SBR-CMC When indigoid, active material, acetylene black (Denka HS-100L), SBR (BM400B) and CMC (BSH-6) were present, a hybrid cathode paste was prepared by mechanically mixing (Thinky Mixer SR-500) them in water. The resulting viscous slurry was uniformly cast onto aluminum foil functioning as a current collector by the doctor blade method, dried at 80 °C under vacuum, roll-pressed to 41 μm with a Rolling Machine (MSK-2150), and 2 an electrode active layer loading of 7.5 mg / cm

[0096] (Example 3) Electrochemical properties a) Redox properties of indigoid: To show the electrochemical properties of this additive, indigo was included in the electrolyte solution and tested in a half-cell by linear sweep voltammetry (LSV) under the following conditions (oxidation vs Al and reduction vs Cu): [Table A]

[0097] The results are shown in Figure 2. Oxidation of indigo can be observed after 4 V, while two reduction reactions occur at about 2 V and 1.3 V. The two reduction reactions are within the LFP / LTO electrochemical window, while oxidation of indigo does not occur in this system. The LSV results are also shown for isoindigo (Figure 19) and indigocarmine (Figure 24).

[0098] For a 1 M LiPF6 solution in PC / EMC (4 / 6) with 10 mMol indigo (the same half-cell as for LSV oxidation), with a scanning rate of 2 mV / s, a maximum voltage of 6 V, a minimum voltage of 1 V, and 3 scans, the same electrochemical solution was also tested by cyclic voltammetry (CV) results (see Figure 3). One irreversible oxidation occurs after 4 V, and two partially reversible reductions occur under the same analysis conditions. The various oxidation states of indigo are shown in Figure 1. CV results are also presented for isoindigo (Figure 18) and indigo carmine (Figure 23).

[0099] b) Electrochemical performance: Before the cycling test, the cells were charged and discharged twice at 0.1C and 25 °C. Here , xC is the current that can fully charge / discharge the cell capacity in 1 / x hours. Charge in CC-CV (constant current constant voltage) mode. Operating conditions: Cells A1, A2, B1, B2 (LFP / Li metal) Voltage: 3.8 V Current: 0.2C Discharge: CC (constant current) mode 0.2C Cut-off voltage: 2 V Current: 0.01C Cells A3 and B3 (LFP / Gr) Voltage: 3.6 V Current: 0.2C Discharge: CC (constant current) mode 0.2C Cut-off voltage: 2 V Current: 0.01C Cells A4, A5, B4 and B5 (LMFP-Li) Voltage: 4.5 V Current: 0.2C Discharge: CC (constant current) mode 0.2C Cut-off voltage: 2 V Current: 0.02C Cells A6, A7, B6 and B7 (NMC-Li) Voltage: 4.2 V Current: 0.2C Discharge: CC (constant current) mode 0.2C Cut-off voltage: 2.5 V Current: 0.01C Cells A8, A10, B8 and B10 (LMFP-LTO) Voltage: 3 V Current: 0.2C Discharge: CC (constant current) mode 0.2C Cut-off voltage: 0.5V Current: 0.02C Cells A9, A11, B9 and B11 (NMC-LTO) Voltage: 2.7V Current: 0.2C Discharge: CC (constant current) mode 0.2C Cut-off voltage: 0.5V Current: 0.01C

[0100] The results at various temperatures are shown in Fig. 4 (Cells A1 and B1-a) and Fig. 6 (Cells A2 and B2-a).

[0101] For example, Fig. 4 shows the comparative discharge results of LFP / Li and LFP(+1%) indigo / Li cells (Cells A1 and B1-a respectively) using a PVdF binder at temperatures in the range of -40°C to 25°C. As can be observed in Table 3 below, the addition of 1% indigo in LFP provides a capacity increase between 4% and 6% between -40 and 25°C.

Table 3

[0102] The discharge results of LFP / Li and LFP(+1%) indigo / Li cells (Cells A2 and B2-a respectively) using an SBR-CMC binder at temperatures between -40°C and 25°C are shown in Fig. 6. Table 4 shows that the addition of 1% indigo to the LFP cathode provides a capacity increase between 1% and 10% at temperatures between -40 and 25°C.

Table 4

[0103] The following Tables 5(a) to 5(c) summarize the capacities and efficiencies of various indigoids tested using a PVdF or SBR-CMC binder. Impedance results considering a reference cell (without indigoid) are also presented.

Table 5

[0104] Cycling data is also presented in Table 6 below, aggregating the retention rate and efficiency of cell B1-a compared to cell A1. It can be observed that lithium cells containing LFP and indigo as an additive show a reduction in capacity loss. It was also observed that indigo-containing cells have more stable efficiency. [Table 6]

[0105] Cells containing graphite as the anode material were also tested. The charge-discharge results of cells A3 and B3-a are shown in Fig. 13. Significant irreversibility can be observed in the first cycle in the presence of indigo. After the first cycle, the battery stabilizes more quickly than the battery without the indigoid additive. Improvement in capacity and reduction in impedance are also observed in the presence of indigo (see below). The impedance results of the LFP / graphite cells with and without indigo (cells A3 and B3-a) are also presented in Fig. 14.

[0106] In cells A7 and B7-a, the cathode material used was NMC(6 / 2 / 2). The cycling results are shown in Fig. 15. It is valuable to note that it is usually very difficult to obtain an NMC-Li battery with cycling performance. As can be observed from Fig. 15, almost all of the capacity is lost after 50 cycles (see reference). On the other hand, when indigo is used as an additive to the NMC cathode, stable capacity and stable efficiency can be obtained for more than 200 cycles. The charge-discharge results of NMC / LTO cells A9 and B9-a are also shown in Fig. 16.

[0107] The charge-discharge results of LFP-Li cells A1 and B1-c with and without isatin are shown in Fig. 20 (PVdF binder), and the charge-discharge results of LFP-Li cells A2 and B2-c with and without isatin are shown in Fig. 21 (SBR-CMC binder).

[0108] Finally, the charge-discharge results of Cells A8 and B8-b using indigo carmine as an additive for the LMFP cathode when using LTO as the anode material are presented in Fig. 25. The addition of indigo carmine in the cathode material showed that the voltage fading typically observed with LMFP was limited.

[0109] c) Electrochemical impedance: Using the LFP-Li cells A1, A2, B1-a, and B2-a described in Example 2, electrochemical impedance spectroscopy (EIS) was also performed at SOC 50% at various temperatures in the range of -40 °C to 25 °C. The frequencies used were 1 MHz to 10 mHz, and at low temperatures 1 MHz to 50 mHz. The AC amplitude was 10 mV. The results are shown in Figs. 5(a) and 5(b) for Cells A1 and B1-a, while Figs. 7(a) and 7(b) show the results obtained for Cells A2 and B2-a.

[0110] Fig. 5 shows the impedance results of LFP / Li and LFP(1% indigo) / Li (Cells A1 and B1-a) using PVdF as the binder. The curve showing two semi-circles, where one represents the resistance related to lithium and the other is related to the resistance of LFP. The results show that at 0 °C and temperatures below, the resistance due to LFP decreases due to the presence of indigo.

[0111] Similar impedance results for LFP / Li and LFP(1% indigo) / Li (Cells A2 and B2-a) using SBR-CMC as the binder are presented in Fig. 7. The results show that at all temperatures tested, the resistance due to LFP decreases due to the presence of indigo.

[0112] The impedances of Cells A2 and B2-a at 25°C were also tested at different states of charge (% SOC). Figure 8 shows these impedance results. In summary, this experiment helps to demonstrate that the presence of indigo improves the diffusion of lithium ions in LFP during charge and discharge, especially at 100% or 80% SOC.

[0113] The impedance results for LFP / graphite cells with and without indigo (Cells A3 and B3-a) are also presented in Figure 14. When graphite was used as the anode, a decrease in impedance was also observed in the presence of indigo.

[0114] Figure 17 shows the impedance results of NMC / LTO Cells A9 and B9-a, with a slight increase observed. Figure 22 presents the impedance results of Cells A1, A2, B1-c, and B2-c using isatin as an additive. A decrease in impedance was observed while using SBR-CMC in combination with isatin.

[0115] Finally, Figure 26 presents the impedance results of Cells A8 and B8-b using indigo carmine as an additive for the LMFP cathode when using LTO as the anode material. The addition of indigo carmine in the cathode material showed a significant reduction in the internal battery resistance.

[0116] As can be observed, when tested at the same temperature, the presence of indigoid generally reduces the impedance of the cell compared to its indigo-free version. This improvement applies to both binders, but is particularly significant when using SBR:CMC as the binder.

[0117] d) Depth of discharge: For the four cells shown in Figure 12 in the following order: cell A1, cell B1-a, cell A2, and cell B2-a, the depth of discharge (% DOD) was evaluated as a function of temperature, the presence or absence of binder and indigo. These comparison results show that the depth of discharge is improved at low temperatures in the presence of indigo in LFP, especially when combined with the use of CMC-SBR as the binder.

[0118] e) Electrolyte stability: For the visual evaluation of the separator, cells A2 and B2-a were opened after cycling (see below the graph in Figure 10). Trace impurities were observed on the surface of the separator in contact with the LFP cathode of the cell without indigo (left image), while no such impurities were present when indigo was used as an additive (right image).

[0119] Next, the separators of both cells were analyzed by Fourier transform infrared (FTIR) spectroscopy. Figure 9(a) shows the FTIR of the separator of cell A2. Peaks observed below 2000 cm -1 are typical of decomposition products of the electrolyte solvent (carbonate). On the other hand, in Figure 9(b) showing the FTIR spectrum of the separator after cycling in the presence of 1% indigo, no such peaks related to the decomposition of the electrolyte were observed.

[0120] The EDS results shown in Figure 10 also demonstrate that the separator of the LFP-Li cell without indigo after cycling (left) presents a very high content of F and P atoms on its surface compared to the corresponding cell with indigo (right). These impurities are typical of electrolyte decomposition (LiPF6).

[0121] Finally, the cathode surface in contact with the battery separator was analyzed by SEM in both the cycled cell B2-a and the control cell A2. The resulting images are presented in Figures 11(a) and (b), respectively. Looking at the cell without indigo (Figure 11(a)), a black zone typically due to electrolyte decomposition is observed. The image of Figure 11(b) showing the material with indigo used as an additive does not present electrolyte decomposition.

[0122] Without departing from the scope of the present invention, numerous modifications can be made to any of the embodiments described above. Any reference, patent, or scientific literature material mentioned in this application is hereby incorporated by reference in its entirety for all purposes.

[0123] According to a preferred embodiment of the present invention, for example, the following is provided. (Item 1) Particles of an electrochemically active material, and formulas I - IV:

Chemical formula

Claims

【Claim 1】 The invention described in the specification.

Images