WO2024039728A1 - Halogenated cationic electrolyte additives for rechargable batteries - Google Patents

Abstract

A rechargeable battery having a dilute halogenated cationic electrolyte additive that has decomposition potentials higher than those of solvent and anions. These additives utilizes electrostatic attraction between halogenated cations and a negatively charged anode, creating a halogen-rich interphase layer at the electrode surfaces. A robust, halogen-rich interfacial layer is formed at the anode, enabling stable cycling of high-capacity anode including, but not limited to, Li-metal. For Li-metal anodes a dendrite-free deposition of dense Li-metal with very high plating/stripping efficiency is achieved. A millimolar addition of halogenated cations improves the oxidation stability of ether-based electrolytes and suppresses the corrosion of the aluminum current collectors, allowing the cycling of battery cells that use high-voltage cathodes.

Description

HALOGENATED CATIONIC ELECTROLYTE ADDITIVES FOR RECHARGABLE BATTERIES

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Provisional Application No. 63/398,320, filed August 16, 2022, the entirety of which is hereby incorporated herein by this reference.

BACKGROUND OF THE INVENTION

[0002] 1 . Field of the Invention

[0003] The present invention generally relates to rechargeable batteries. More particularly, the present invention relates to rechargeable batteries having one or more metal electrodes, including lithium-ion, lithium metal and post-lithium energy storage (e.g. sodium ion, potassium, calcium, magnesium ion, and metal batteries). [0004] 2. Description of the Related Art

[0005] Battery energy density is strongly affected by the capacity of the anode and cathode materials, their loading, and their respective electrochemical potentials. Anode and cathode materials in the commercial Li-ion batteries can no longer offer desired improvements in energy density due to their relatively low theoretical (and experimental) capacities. Therefore, the implementation of high energy anode and cathode materials serves as a key next step. To meet the demands for rechargeable batteries with high energy densities of 400-500Wh/kg it is highly desirable to use thin Li-metal anodes.

[0006] The high reactivity of Li leads to capacity loss via irregular, dendritic deposition on the electrode surface and facilitates degradation of liquid electrolyte. Lithium dendrites, with needle/tree-like structures, can also reach out to the opposite electrode, ultimately resulting in internal short-circuiting of the battery and thermal runaway of the cell. At a minimum, dendritic growth causes constant reformation of the interface, electrolyte consumption in the battery, loss of efficiency, and eventual cell failure. Even more dramatic is the degradation of other alkali and alkali-earth metal anodes (e.g. Na), which face similar challenges.

[0007] In a similar sense, charging conditions for high voltage cathodes (the use of which is important to obtain high energy density batteries) often lie outside the stability window of the solvent, leading to solvent consumption and decomposition, as well corrosion of the cathode materials and current collectors and hence fast cell degradation.

[0008] In batteries, electrolytes, which are a combination of organic solvent with a salt, decompose on the anode surface and form an electrode/electrolyte interphase layer called the solid-electrolyte interphase (SEI). Properties of the SEI directly affect the performance of battery cells. When the SEI is electronically insulating, but ionically conductive it plays the role of a protective film that prevents further decomposition of electrolyte components and allows for stable operation of battery cells. Thus, a stable and intact SEI layer is necessary for long-term performance of battery cells.

[0009] There has been a trend to replace traditional intercalation anodes, such as graphite and lithium-titanium-oxide, with Li-metal that can enable battery cells with specific energies that are almost doubled, providing an attempted solution to the current energy density bottlenecks for batteries. However, Li-metal anodes are prone to developing dendritic and porous (mossy) deposits during repetitive charge/discharge cycling. This leads to an unacceptably low cycle life and introduces serious safety concerns, prohibiting practical widespread implementation of Li-metal batteries.

[0010] The SEI layer plays a critical role in stabilizing highly reactive anodes such as Li metal (when replacing graphite and other intercalation anodes in high-energy density rechargeable batteries), which improves in particular the Li plating/stripping process and, hence, the cycle life of such Li-metal batteries. The SEI is a layer formed on the electrode surface due to decomposition of electrolyte and thus contains decomposition products of the electrolyte components such as solvent, salt, and molecular additives. Electrolyte composition is thus known to dramatically affect the properties of the resulting SEI (structure, chemistry, and homogeneity) and lithium plating/stripping efficiency, morphology and, hence, cycle life. Commercial Li- ion electrolyte chemistries are based on carbonate solvents and Li-ion salts that were originally developed and optimized for graphite anodes. However, when carbonate-based electrolytes are used in combination with Li-metal anodes, they yield highly unsatisfactory cycle life due to unfavorable SEI chemistry at the Li-metal surface. Specifically, structural instability and heterogeneity of the SEI results in uncontrolled SEI growth and the formation of electronically disconnected “dead lithium” and/or dendrites. Therefore, the development of new electrolytes that can yield favorable SEI structure and composition on Li-metal electrodes constitutes a critical direction in the improvement of Li-metal batteries.

[0011] Recent research suggests that a fluorine-rich, or more generally halogenrich, SEI layer yields superior performance when compared to a halogen-free SEI layer. To achieve a fluorine-rich SEI layer, current approaches rely on a large volume fraction of fluorinated species in the electrolyte that have a statistically higher probability of being reduced at the electrode surface and, therefore, engender fluorine-rich interfacial chemistry. For example, solvent-in-salt electrolytes with a high concentration of fluorine-containing (or more generally halogen-containing) anions yield a fluorine-rich SEI and an improved coulombic efficiency compared to their dilute counterparts. Another strategy relies on halogenated solvents that can participate in the formation of the SEI layer. Yet, despite enabling promising performance, these existing approaches have notable drawbacks when it comes to their practical implementation.

[0012] The high cost of Li salts and increased solution viscosity at high salt concentration makes highly concentrated electrolytes challenging for commercial battery applications. Similarly, the replacement of conventional solvents with heavily fluorinated ones can lead to a substantial increase in battery costs. Furthermore, fluorine is an environmental contaminant and is disfavored in bulk use in industrial processes. Accordingly, an electrolyte that can advantageously form a fluorine-rich SEI layer without these disadvantages represents an improvement in battery technology and a way towards economical implementation of high energy anodes and cathodes.

[0013] The present invention is applicable to address an additional challenge related to corrosion mitigation from solvent decomposition as well as utilization of imide- based lithium salts, including but not limiting to compounds such as Lithium Bis(fluorosulfonyl)imide (LiFSI) and Lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Imide-derived lithium salts offer improved physicochemical and electrochemical properties, most importantly higher ionic conductivity compared to conventional lithium battery salts, such as LiPFe. However, their implementation in commercial batteries has been challenged by increased vulnerability of the cathode surface and Al current collectors to corrosion when such salts of moderate purity are applied. This susceptibility is due to the absence of a robust protective layer as a result of the compromised integrity of the cathode-electrolyte interface (CEI).

BRIEF SUMMARY OF THE INVENTION

[0014] Briefly described, the present system and method utilize a new approach that relies on the electrostatic attraction of functional cationic additives that possess high decomposition potential (~1 to 3 V vs Li/Li⁺) to a negatively charged anode, e.g. a Li-metal anode (but not limited to such anodes). Through this approach, a significant population of such species can reach the electrode surface of a battery even when the overall concentration in the bulk electrolyte is in the millimolar range and as low as 0.1 wt. %. Upon charging the battery, these species undergo decomposition due to their high reduction potentials (earlier than solvent and other electrolyte components) and releasing species facilitating formation of a robust SEI layer with favorable composition.

[0015] A broad structural range of functional cationic additives are possible, including halogenated (fluorinated, chlorinated, brominated) pyridinum, imidazolium and ammonium cations. More particularly, on the anode side the present invention relies on the use of functional organic cations with early decomposition potentials (~1 to 2.6 V vs Li/Li+) and their electrostatic attraction to negatively charged anode of such battery in order to facilitate the dominant contribution of such functional cations in forming a solid electrolyte interphase (SEI), even when such additives are used at low overall fractions (<1 wt.%). Thus, the present invention allows stabilization of anode interphases, and facilitates control of such SEIs including control over composition and homogeneity. On the cathode side, the proposed cationic additives support the formation of favorable cathode electrolyte interphase (CEI) during decomposition of these cations at electrode surfaces. Hence, the invention presents a general approach toward controlled formation of SEI and CEI in rechargeable batteries using functional cationic additives. Interphase stabilizing properties of the additives enable extension of the cycle life of a battery, while keeping the costs low (since only small amounts of such additives are necessary to form robust battery interphases on both anodes and cathodes). These additives are compatible with existing battery manufacturing lines, as they can be easily added to any liquid electrolyte formulation. [0016] In one embodiment, the invention includes a battery having a Li-metal or bare Cu current collector as an anode, an oxide cathode, and an electrolyte is between the anode and cathode. The electrolyte contains functional organic cations that undergo reductive decomposition on the anode surface, thus releasing fluorine- rich (or generally halogen-rich) components that build up a robust halogen-rich interfacial layer.

[0017] In one embodiment, the electrolyte uses fluorinated pyridinium cations (in a form of perchlorate or triflate salt) that can offer early decomposition potentials of ~2 V vs. Li/Li⁺. The addition of such cations even in millimolar amounts (as little as 0.1- 0.3 percent by weight) to a conventional ether-based electrolyte, enables dendrite- free plating of dense Li with a coulombic efficiency >99 %. Furthermore, the prolonged cycling of Ni-rich high-voltage cathodes in ether-based electrolytes can be achieved by suppressing oxidative decomposition of the electrolyte upon addition of small amounts of these functional cationic additives.

[0018] In one embodiment, the functional cationic additives are present in the electrolyte at millimolar amounts (or as little as 0.1 percentage by weight or more). The electrolyte can be an ether-based electrolyte, such as dimethoxy ethane or it can be based on any other organic solvent in which functional cationic additive doesn’t undergo hydrolysis (e.g. organic carbonates, nitriles, ethers, etc.). Furthermore, the Li-metal battery can include an high voltage cathode, such as NCM811 , on an aluminum current collector, with the battery showing at least 300 cycles of stable charge and discharge.

[0019] In a further embodiment, the invention includes a method of creating a halogen-rich interfacial layer on a battery anode by the steps of adding an electrolyte containing positively charged halogenated cations into battery assembly (coin-cell, pouch, cylinder etc.). Then, by applying negative charge to the anode (i.e. reducing electrochemical potential), forming a halogen-rich interfacial layer, SEI, on the electrode surface.

[0020] The present invention further provides an advantage in that it allows to suppress oxidative decomposition of the electrolyte (e.g. ether) as well as Al current collector corrosion at the cathode. These benefits come together with described above stabilization of anode interphase that enable extended cycle-life and efficiency of high-energy batteries that feature next generation anode materials such as Li- metal. The present invention is also easily industrially adaptable as it can utilize already existing manufacturing lines for Li-ion batteries since the additive can be readily incorporated to liquid electrolyte formulations. Accordingly, these and other advantages and benefits of the present invention will become apparent to one of skill in the art after review of the present specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Fig. 1A is a schematic diagram of a solid electrolyte interphase (SEI) layer formation from a fluorinated cationic additive (FCA) on anode. Fig. 1A also includes the molecular structure and electrochemical reduction/oxidation potentials of the FCA.

[0022] Fig. 1 B is a graph of a first and second cycle of cyclic voltammetry collected in dimethoxy ethane (DME) + 1 M LiFSI electrolytes with and without fluorinated cations.

[0023] Fig. 1C is a graph of galvanostatic cycling of a Li°-Li° symmetric cell at 10 mA cm² using 1 M LiFSI in DME as an electrolyte with and without fluorinated cations.

[0024] Fig. 1 D is a graph of a zoomed-in profile of the cycling in Fig. 1 C using 1 M LiFSI in DME as an electrolyte with and without fluorinated cations.

[0025] Fig. 1 E is a graph of a zoomed-in profile of the cycling in Fig. 1 C using 1 M LiFSI in DME as an electrolyte with fluorinated cations.

[0026] Fig. 1 F is an image of cross-sectional scanning electron microscope (SEM) images of a cycled Li-metal anode after 1852 cycles in 1 M LiFSI DME electrolyte.

[0027] Fig. 1G is an image cross-section scanning of a Li-metal anode after 2000 cycles in electrolyte with 12 mM FCA, showing film morphologies.

[0028] Fig. 2A is a graph of the long-term cycling of NCM8111| Li full-cells with different electrolytes.

[0029] Fig. 2B is a graph of the voltage profile of NCM811 ||Li full-cells at 0.1 C-rate and 1 C-rate.

[0030] Fig. 3A is an SEM image of a cycled Li metal anode after 1852 cycles, without a FCA additive.

[0031] Fig. 3B is an SEM image of a cycled Li metal anode after 2000 cycles with FCA additive. [0032] Fig. 4A is an SEM image of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI with higher purity level after 20 cycles at 1C.

[0033] Fig. 4B is an SEM image of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI + 12 mM FCA with higher purity level of LiFSI salt after 20 cycles at 1 C.

[0034] Fig. 4C is an SEM image of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI with lower purity level of LiFSI salt after 20 cycles at 1C.

[0035] Fig. 4D is an SEM image of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI + 12 mM FCA with lower purity level of LiFSI salt after 160 cycles at 1C.

[0036] Fig. 5 is a diagram of the chemical synthesis of the pyridinium-based cations and range of possible other structures containing functional imidazolium- and ammonium-based cations that can be used to stabilize anode and cathode battery interphases, while being used in amounts as little as 0.1 wt. %.

DETAILED DESCRIPTION

[0037] With reference to the figures in which like numerals represent like elements throughout the several views, the present invention is a new approach in rechargeable batteries including Li-ion, Li-metal and post-Li batteries, that relies on the electrostatic attraction of functional cationic additives, including but not limiting to fluorinated pyridinium cations, to a negatively charged anode (32, Fig. 1A), such as Li metal anode (or other anode materials), in combination with their high reduction potentials (~1 to 2.6 V vs Li/Li⁺; earlier than other electrolyte constituents such as solvent or anions, Fig. 5).

[0038] Through this approach, a significant population of such cationic species can reach the electrode surface even when the overall concentration in the bulk electrolyte is in the millimolar range. Upon charging the battery, such additives undergo reductive decomposition releasing species that are favorable for robust SEI formation on such anodes. Hence, these additives are predominantly contributing to SEI species and thereby allow for control over chemical and structural composition of SEI (as schematically depicted in Fig 1 A). As such, fluorinated pyridinium cations offer early decomposition potentials of ~2 V vs. Li/Li+, and the addition of fluorinated pyridinium cations even in millimolar amounts (as little as 0.1 percentage by weight) to a conventional electrolyte based on dimethoxy ethane (DME) enables dendrite- free plating of dense Li with a coulombic efficiency of >99%. Furthermore, prolonged cycling of Ni-rich high-voltage cathodes in ether-based electrolytes is achieved by suppressing oxidative decomposition of the electrolyte upon addition of small amounts of fluorinated cations, thus allowing the exploration of other solvent families such as (organic carbonate, ethers, nitriles and other).

[0039] Fig. 1A is a schematic diagram 10 of a solid electrolyte interphase (SEI) layer 12 formation from a fluorinated cationic additive on a Li-metal anode 32. Fig. 1 B is a graph 14 of the first and second cycle of CV collected in dimethoxy ethane (DME) + 1 M LiFSI electrolytes with and without fluorinated cations on a 1 mm Cu disk working electrode with 0.5 mV/s scan rate.

[0040] Fig. 1C is a graph 16 of Galvanostatic cycling of a Li°-Li° symmetric cell at 10 mA cm'² using 1 M LiFSI in DME as an electrolyte with and without fluorinated cations. The Galvanostatic cycling of the Li°-Li° symmetric cell was at 10 mA cm^-2 using 1 M LiFSI in DME as an electrolyte with and without fluorinated cations. Fig. 1 D and Fig. 1 E are graphs 18 and 20 of a zoomed-in profile of the cycling in Fig. 1C.

[0041] Figs. 1 F-1G are cross-sectional SEM images of the cycled Li-metal anodes 32. Fig. 1 F is an image 22 of cross-sectional scanning electron microscope (SEM) images of a cycled Li-metal anode 32 after 1852 cycles in 1 M LiFSI DME electrolyte. Fig. 1G is an image 24 of a cross-sectional scanning of a Li-metal anode 32 after 2000 cycles in electrolyte with 12 mM FCA, showing film morphologies. The scale bar is 5 pm. Before SEM, a lamella (5 pm deep) was cut out using cryo-FIB. [0042] The present invention takes advantage of the effect of fluorinated cations on cycling of lithium metal anodes (anode 32). Halogenated methylpyridinium cations are advantageous because: (1) previous experiments showed pyridinium-based cations undergo reductive decomposition at -1.75 V vs. Li/Li⁺, which is well above the decomposition potentials of nonaqueous solvents and anions; and (2) quantumchemical calculations indicate that fluorination of methylpyridinium cations would further shift the reduction potential to even higher values, providing a simple pathway for the formation of fluorine-rich SEI. Here, N-methyl-2,4,6-trifluoropyridinium (TFP) is used as a fluorinated cationic additive. As the baseline electrolyte, 1 M lithium bis(fluorosulfonyl)imide (LiFSI) in DME is used because it shows one of the highest coulombic efficiencies for Li plating/stripping among additive-free electrolyte formulations.

[0043] To demonstrate the efficacy of the present invention, cyclic voltammetry (CV) profiles collected in additive-containing electrolytes show a pronounced reduction peak at -1.98 V vs. Li/Li⁺ (Fig. 1 B) during the 1^st cycle, which is absent in the additive-free electrolyte. This peak disappears in the 2^nd cycle, consistent with passivation of the anode 32 surface, preventing further reduction of fluorinated cations. These experiments confirm that the reduction of fluorinated cations occurs at potentials nearly -1 .5 higher than the onset of decomposition of the additive- free electrolyte.

[0044] To quantify how the addition of fluorinated cations affects the coulombic efficiency of Li plating/stripping, a Aurbach protocol was used. The test revealed a substantial improvement of average coulombic efficiency from 96.4% for the TFP- free electrolyte to 99.6% for the cells containing TFP (-0.1 percentage by weight). This efficiency is comparable to those reported for the best-performing extant electrolytes containing fluorinated solvents or salts in high concentrations, demonstrating that large fractions of fluorinated species in electrolytes can be avoided when aiming for high coulombic efficiencies.

[0045] Importantly, the morphology of Li-metal anode 32 correlated with the evolution of overpotential with cycling. Initially, comparable overpotentials and similar Li morphology were observed for both electrolytes. After 1 ,852 cycles, for the additive-free electrolyte a rough Li surface with multiple cracks can be seen by scanning electron microscopy (Fig. 1 F), with highly porous Li deposits and in agreement with prior studies. In contrast, a smooth surface with large and dense Li grains was observed for Li that was cycled 2000 times in the electrolyte containing fluorinated cations, as shown in Fig. 1G.

[0046] In one embodiment, the electrolyte 36 uses fluorinated pyridinium cations that can offer early decomposition potentials of -2 V vs. Li/Li+. The addition of fluorinated pyridinium cations even in millimolar amounts (0.05-0.5 percent by weight) to a conventional electrolyte based on dimethoxy ethane (DME) enables dendrite-free plating of dense Li with a coulombic efficiency above 99.2%. Furthermore, the prolonged cycling of Ni-rich high-voltage cathodes in ether-based electrolytes is achieved by suppressing oxidative decomposition of the electrolyte upon addition of small amounts of fluorinated cations.

[0047] The origin of the superior cycling performance of the Li-metal anode 32 in TFP-containing electrolytes, studies of the SEI layers formed in the presence of TFP using X-ray photoelectron spectroscopy (XPS). The XPS data collected from cycled Cu electrodes revealed a high fluorine: carbon (F:C) atomic ratio for the SEI formed in the presence of cationic additives (F:C = 3.1 - 4.5), whereas no fluorine was detected for the SEI generated in reference electrolyte. This indicates a dramatically decreased relative contribution of the solvent decomposition products. Furthermore, analysis of F 1 s and Li 1 s spectra revealed Li F as a dominant species for SEI samples obtained in the presence of fluorinated cations. This indicates that even millimolar addition of the fluorinated cations can yield favorable F-rich SEI.

[0048] The improvement of the energy density of the batteries requires coupling of Li-metal anodes 32 with high-voltage cathodes, such as those coated onto an aluminum (Al) current collector. In general, high-voltage cathode 34 materials cannot be used in non-concentrated DME-based electrolytes due to the oxidative decomposition of DME solvent above 4 V vs. Li/Li⁺. Therefore, the stability of DME- based electrolytes with fluorinated cations was examined using cyclic voltammetry in the potential range from 3.0 V to 5.0 V (vs. Li/Li⁺) on an Au disk electrode (Fig. 3A). The onset potential for the oxidative decomposition is shifted by +0.4 V (at 0.5 mA/cm²) when fluorinated cations are added to the electrolyte. The improved oxidation stability of the electrolyte with an additive is due to the formation of cathode electrolyte interphase (CEI) (Fig. 2B).

[0049] Fig. 2A is a graph 60 of the long-term cycling of NCM81111 Li full cells with different electrolytes 36 (0.1 C-rate for three cycles and 1 C-rate for 50 cycles in a loop). Fig. 2B is a graph 62 of the voltage profile of NCM81111 Li full-cells at 0.1 C- rate and 1 C-rate.

[0050] The increase in oxidation stability of the DME-based electrolyte having a concentration of just 12 mM of fluorinated cation (Fig. 2A) implies that such electrolytes can be used with high voltage cathodes. Therefore, as a next step we performed galvanostatic cycling using a LiNio sCoo.i Mn 0.1O2 (NCM811) cathode 34 and a Li-metal anode 32 in a coin-cell configuration. Without fluorinated cations, the cells show severe capacity fading and rapid decreases in CE value within 50 cycles, in agreement with known earlier studies. In contrast, cells with fluorinated cations demonstrated a dramatic improvement in cycling stability even for the concentration of 4 mM, with the optimal being about 12 mM. The NCM81111 Li full cells with the electrolyte containing fluorinated cations maintained 83.5% of the 1C discharge capacity retention even after 300 cycles and demonstrated a coulombic efficiency close to 100% (99.8% at the 256^th cycle).

[0051] The charge/discharge voltage profiles (Fig. 2B) show that the cells containing fluorinated cations can be successfully and repetitively charged up to 4.2 V. The differential capacity profiles (dQ/dV) for the cells with TFP showed both phase transitions expected for the NCM811 cathode 34 during charging/discharging [from hexagonal (H1) to monoclinic (M) occurring between 3.6 V and 3.8 V and from monoclinic to hexagonal (H2) at ~4.0 V], This contrasts with the cells without additive that showed severe discharge capacity fading during charging up to 4.2 and a failure to undergo the second phase transformation during charging due to electrolyte decomposition. Electrochemical impedance spectroscopy data also show a minimal increase in impedance with cycling for the full cells with TFP in agreement with the cells’ dQ/dV profiles.

[0052] The improved oxidation stability of the electrolyte and stable cycling of NCM81111 Li cells with fluorinated cations is due to the formation of a favorable cathode electrolyte interphase (CEI). Cycled NCM811 shows that the CEI has a substantial amount of fluorine only in the TFP-containing electrolyte and not the reference one, indicating an active role of fluorinated cations in CEI formation.

[0053] The presence of TFP in the electrolyte helps to suppress current collector corrosion. SEM images of the Al current collectors that supported the NCM811 cathode showed that after 160 cycles in the electrolyte with fluorinated cations, the current collector had no signs of corrosion, while in the additive-free electrolyte a significant roughening of the Al current collector was observed already after 20 cycles.

[0054] Fig. 3A-3B are SEM images of the long-term cycled Li metal electrode. Fig. 3A is an image 70 of a cycled Li metal anode after 1852 cycles, without a TFP additive. The Galvanostatic cycling of a Li°-Li° symmetric cell at 10 mA cm^-2 was used with 1 M LiFSI in DME for the reference sample. Fig. 3B is an image 72 of a cycled Li metal anode after 2000 cycles with a TFP additive. The sample was in DME 1 M LiFSI + 10 mM TFP for the additive-containing sample.

[0055] Figs. 4A-4D are SEM images of the Al current collectors on NCM811 cathode material. Fig. 4A is an image 80 of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI with higher purity level after 20 cycles at 1C. Fig. 4B is an image 82 of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI + 12 mM TFP with higher purity level after 20 cycles at 1C. Fig. 4C is an image 84 of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI with lower purity level after 20 cycles at 1 C. Fig. 4D is an image 86 of Al current collectors on NCM811 cathode material using DME + 1 M LiFSI + 12 mM TFP with lower purity level after 160 cycles at 1C. Thus, it was demonstrated that the addition of TFP effectively inhibited Al corrosion at the electrode.

[0056] Fig. 5 is a diagram 88 of the structure representations of the chemical synthesis of several embodiments of the pyridinium-based cations and range of other possible structures containing functional imidazolium- and ammonium-based cations that can be used to stabilize anode and cathode battery interphases, while being used in amounts as little as 0.1 wt. %. These additives can be incorporated into electrolyte formulations that are based on different solvent families (organic carbonate, ethers, nitriles etc.). These additives are to be introduced into electrolyte in a form of salt, where anions can be varied in wide range (OTf; CIC , FSI; TFSI; NOs' etc ).

[0057] It can thus be seen that, in one embodiment, the invention includes an electrolyte for a metal batter comprising a solvent and lithium ion salt, and a fluorinated cationic additive, the FCA present in the electrolyte in a millimolar amount less than 0.3 percentage by weight, wherein upon the electrolyte contacting the surface of a negatively charged electrode (such as Li-metal anode 32), on the electrode surface 33 a fluorine-rich interfacial layer is formed (such as SEI layer 12) of the electrode (e.g. Li-metal anode 32). The electrolyte can contain halogenated pyridinium-based or imidazolium-based cations, such as (but not limited to) those shown in Fig. 5.

[0058] The cationic additive can promote formation of a halogen-rich interfacial layer (SEI 12) at the surface 33 of the anode (e.g. Li-metal) even if overall cationic additive concentration is in millimolar range (as little as 0.05 percent by weight), and the halogenated cations can be present in the electrolyte 36. Furthermore, the electrolyte 36 can include a dimethoxy ethane as a solvent, however other organic solvents can be used as well.

[0059] The invention can also include, in one embodiment, a method of creating a fluorine-rich interfacial layer (SEI 12) on an electrode 32 of a Li-metal battery 30 through placing an electrolyte in a metal battery 30, the metal battery 30 including a metal electrode (such as Li-meal anode 32 or cathode 34) having a surface 33 thereof, the electrolyte 36 containing positively charged fluorinated cations. The method continues with negatively charging the Li-metal electrode (anode 32 or cathode 34) and forming a fluorine-rich interfacial layer (such as SEI 12) on the electrode surface 33 from the positively charged fluorinated cations in the electrolyte. [0060] The method can include placing an electrolyte 36 having halogenated pyridinium-based and imidazolium-based cations. The method can also include forming the halogen-enriched interphases on the electrode surface (anode and cathode) at very low overall additive amounts (millimolar concentrations, as little as 0.05 percent by electrolyte weight). The method can be embodied as placing an ether-based electrolyte 36, such as a dimethoxy ethane electrolyte.

[0061] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below, if any, are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. The embodiment was chosen and described in order to best explain the principles of one or more aspects of the invention and the practical application, and to enable others of ordinary skill in the art to understand one or more aspects of the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

CLAIMS What is claimed is:

1 . A rechargeable battery, comprising: an anode having a surface thereof and selectively receiving a negative charge; a cathode; and an electrolyte between the anode and cathode, the electrolyte containing halogenated cations, wherein upon the anode being negatively charged, organic functional cations that have high decomposition potentials decompose on, at least, the surface of the anode to create a halogen-rich interphase layer thereat.

2. The battery of claim 1 , wherein positively charged halogenated cations are halogenated pyridinium-based or imidazolium-based cations.

3. The battery of claim 1 , wherein the halogenated cations are present in the electrolyte are in a millimolar amount at 0.05-0.5 percentage by weight.

4. The battery of claim 1 , wherein the electrolyte is an ether-based electrolyte.

5. The battery of claim 1 , further including a cationic additive based on one of or a combination of organic carbonates, ethers, nitriles, and phosphates.

6. The battery of claim 5, wherein the electrolyte is based on dimethoxy ethane.

7. The battery of claim 1 , wherein the cathode includes an aluminum current collector.

8. The battery of claim 1 , wherein the battery is rechargeable and cycles through charge and discharge phases.

9. An electrolyte for a battery, comprising: a solvent; a salt; and a halogenated cationic compound; wherein upon polarization the electrolyte from contacting a surface of a negatively charged anode, a halogen-rich interfacial layer forms at the surface of the anode.

10. The electrolyte of claim 9, further containing halogenated pyridinium or imidazolium cations.

11 . The electrolyte of claim 9, wherein the halogenated cations are present in the electrolyte are in a millimolar amount between 0.5-5 percentage by weight/volume.

12. The electrolyte of claim 9, further including a dimethoxy ethane compound.

13. A method of creating a halogen-rich interfacial layer on an electrode of a rechargeable battery, comprising: placing an electrolyte in a rechargeable battery, the rechargeable battery including an electrode having a surface thereof, the electrolyte containing halogenated cations; negatively charging the charging; and forming a halogen-rich interfacial layer on the electrode surface from the halogenated cations in the electrolyte.

14. The method of claim 13, wherein placing an electrolyte is placing an electrolyte having halogenated pyridinium or imidazolium cations.

15. The method of claim 13, wherein forming the halogenated cations is forming the halogenated cations such that they are present in the electrolyte are in a millimolar amount of 0.5-5 percentage by weight.

16. The method of claim 13, wherein placing the electrolyte is placing an ether-based electrolyte.

17. The method of claim 16, wherein placing the electrolyte is placing a dimethoxy ethane electrolyte.

18. A rechargeable battery, comprising: an anode having a surface thereof and selectively negatively charged; a cathode having a surface thereof; and an electrolyte between the anode and cathode, the electrolyte containing halogenated cations, wherein upon the anode being negatively charged, organic functional cations having high decomposition potentials decompose on the anode surface and cathode surface thereby creating halogen-rich interphase layers thereat.