Ultra-low temperature rechargeable li / CL2 batteries with thionyl chloride electrolytes

Abstract

An electrochemical device is configured for operation at a temperature of about -85°C to about -20°C. The electrochemical device includes a negative electrode comprising lithium metal, a positive electrode comprising a conductive carbon material having a pore volume of about 6.1 cm3 g-1 to about 7 cm3 g-1, and an electrolyte, wherein the electrolyte comprises aluminum chloride present in a concentration of about 0.5 M to about 1.2 M in thionyl chloride.

Description

ULTRA-LOW TEMPERATURE RECHARGEABLE Li / Cl2BATTERIES WITH THIONYL CHLORIDE ELECTROLYTESGOVERNMENT RIGHTS

[0001] This invention was made with government support under Contract No. ECCS- 2026822 awarded by the National Science Foundation to the Board of Trustees of the Leland Stanford Junior University. The government has certain rights in the invention.FIELD

[0002] The present technology is generally related to batteries that operate at low temperatures. Specifically, the present technology is related to Li / Ch batteries with thionyl chloride electrolytes that operate at low temperatures (e.g., -85°C to -20°C).BACKGROUND

[0003] The following description of the background of the present technology is provided simply as an aid in understanding the present technology and is not admitted to describe or constitute prior art to the present technology.

[0004] Conventional rechargeable batteries underperform at temperatures of about -30°C or lower, with reduction in battery capacity and cycle-life, limiting the operation of electronic devices, electric vehicles and equipment in polar climates, and subsea and space explorations. Li-ion batteries with ethylene carbonate (EC)-based electrolytes can only operate at temperatures as low as about -20°C. EC-based electrolytes are limited by decreased ionic conductivity, slower interfacial charge transfer kinetics and Li+ transport in electrodes at lower temperatures.SUMMARY

[0005] In one aspect, which may be combined with any other aspect or embodiment, an electrochemical device is disclosed. The electrochemical device comprises a negative electrode comprising lithium metal; a positive electrode comprising a carbonaceous material having a pore volume of about 6.1 cm3g-1to about 7 cm3g-1; and an electrolyte,wherein the electrolyte comprises aluminum chloride present in a concentration of about 0.5 M to about 1.2 M in thionyl chloride. In some embodiments, the carbonaceous material has a mesopore volume of about 6.1 cm3g-1to about 7 cm3g-1or about 6.5 cm3g-1to about 7 cm3g-1.

[0006] In some embodiments, the carbonaceous material may be treated by heating the carbonaceous material at about 900°C to about 1100°C in the presence of CO2, N2, water, or a combination thereof. In some embodiments, the carbonaceous material may have a surface area of about 2000 m2g-1to about 3000 m2g-1. In some embodiments, the positive electrode may further comprise lithium chloride deposited on the carbonaceous material. The positive electrode may further comprise LiCl, SOCI2, Ch, SCI2, S2CI2, or SO2CI2 within pores of the carbonaceous material. In some embodiments, the positive electrode may further comprise nickel foam and the carbonaceous material may be deposited on the nickel foam.

[0007] In some embodiments, the electrolyte may also include lithium chloride and lithium bis(trifluoromethanesulfonyl)imide. The electrolyte may include aluminum chloride present in a concentration of about 0.9 M to about 1.1 M. In some embodiments, the electrolyte may include lithium chloride present in a concentration of about 0.7 M to about 1.2 M. The electrolyte may include lithium bis(trifluoromethanesulfonyl)imide present in a concentration of about 0.02 M to about 0.08 M. In some embodiments, the electrolyte may have a viscosity at -40°C that is about 3 times higher than the viscosity at 20°C.

[0008] In another aspect, which may be combined with any other aspect or embodiment, a method of cycling an electrochemical device is disclosed. In some embodiments, the method comprises operating the electrochemical device at a temperature of about -85°C to about -20°C; wherein the operating comprises delivering a specific capacity of about 1000 mAh g-1to about 5000 mAh g-1over at least 50 electrochemical cycles using the electrochemical device; and wherein an electrolyte in the electrochemical device comprises a metal halide and thionyl chloride. In some embodiments, the method comprises operating the electrochemical device at a temperature of about -85°C to about -35°C; wherein the operating comprises delivering a specific capacity of about 1000 mAh g-1to about 5000 mAh g-1over at least 50 electrochemical cycles using theelectrochemical device; and wherein an electrolyte in the electrochemical device comprises a metal halide and thionyl chloride.

[0009] In some embodiments, operating the electrochemical device may be performed at about -75°C to about -85°C and may comprise delivering a specific capacity of about 1100 mAh g-1to about 1200 mAh g-1over at least 70 electrochemical cycles. In some embodiments, operating the electrochemical device may be performed at about -35°C to about -45°C and may comprise delivering a specific capacity of about 2400 mAh g-1to about 2500 mAh g-1over at least 70 electrochemical cycles. In some embodiments, operating the electrochemical device may be performed at about -35°C to about -45°C and may comprise delivering a specific capacity of about 1100 mAh g-1to about 1200 mAh g-1over at least 100 electrochemical cycles.

[0010] In some embodiments, the metal halide in the electrolyte may include aluminum chloride present in a concentration of about 0.5 M to 1.2 M. In some embodiments, the metal halide in the electrolyte may include lithium chloride present in a concentration of about 0.7 M to 1.2 M. In some embodiments, the electrolyte may further include lithium bis(trifluoromethanesulfonyl)imide present in a concentration of about 0.02 M to 0.08 M.

[0011] In another aspect, which may be combined with any other aspect or embodiment, a positive electrode for an electrochemical device is disclosed. The positive electrode comprises a substrate comprising a nickel foam, stainless steel, or a combination thereof; and a carbonaceous material deposited on the substrate. In some embodiments, the carbonaceous material has a mesopore volume of about 6.1 cm3g-1to about 7 cm3g-1and a surface area of about 2000 m2g-1to about 3000 m2g-1. In some embodiments, the carbonaceous material is treated by heating the carbonaceous material in the presence of CO2 at about 900°C to about 1100°C. In some embodiments, the carbonaceous material has a mesopore volume of about 6.5 cm3g-1to about 7 cm3g-1.BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIGS. 1A-1E are directed to a high-capacity lithium-chlorine (i.e., Li / Ch) battery through the first discharge at room temperature. FIG. 1A is a schematic drawing of the Li / Ch battery with an initial electrolyte composition and an activated carbon positive electrode. FIG. IB is a scanning electron microscopy (SEM) image of pristineKETJENBLACK® carbon. FIG. 1C is an SEM image of high-temperature-activated KETJENBLACK® carbon (KJCO2). FIG. ID is a graph of the first discharge curves of room temperature batteries using either KETJENBLACK® (KJ) or activated KETJENBLACK® (KJCO2) recorded at 50 mA g'1. FIG. IE is a graph of the average measured BET surface area and pore volume (micropores and mesopores) of pristine KETJENBLACK® (KJ) or activated KETJENBLACK® (KJCO2). The loading of KETJENBLACK® or activated KETJENBLACK® was about 2.0 mg cm-2in the positive electrode.

[0013] FIGS. 2A-2H are directed to high-capacity Li / Ch batteries through their first discharge at temperatures of -20°C, -40°C, and -80°C. FIG. 2A is a graph of the first discharge curves of Li / Ch batteries with KJCO2 positive electrodes at -20°C, -40°C, and -80°C, respectively. The current was 50 mA g-1for -20°C and -40°C experiments, and 12.5 mA g-1for -80°C experiments. FIG. 2B is a graph of X-ray diffraction (XRD) of a pristine KJCO2 electrode (bottom), the KJCO2 electrode after the battery’s first discharge at room temperature (middle), and the KJCO2 electrode after the battery’s first discharge at -40°C (top). LiCl was formed on the KJCO2 electrode after the first discharge, indicated by strong LiCl XRD peaks. FIG. 2C is a schematic drawing of LiCl deposition in the pores and on the surface of KJCO2. FIG. 2D is a graph of the measured ionic conductivity of the electrolyte (1.0 M AICk + 0.95 M LiCl dissolved in SOCh with 0.05 M of LiFSI additive) at different temperatures. FIGS. 2E-2H are SEM images of KJCO2 electrodes after the first discharge at RT, -20°C, -40°C, and -80°C, showing different morphologies / reduced sizes of the deposited LiCl. The loading of KJCO2 was about 2.0 mg cm'2on the positive electrodes of all batteries.

[0014] FIGS. 3A-3F are directed to the cycling characteristics of Li / Ch batteries with KJCO2 positive electrodes at -40°C. FIG. 3A is a graph of the cycling performance of a Li / Ch battery with a KJCO2 positive electrode (KJCO2) with 1200 mAh g-1cycling capacity under 100 mA g-1current at -40°C. FIG. 3B is a graph of the cycling performance of a Li / Ch battery with a KJCO2 positive electrode (KJCO2) at 2500 mAh g-1cycling capacity under 100 mA g-1current at -40°C. FIG. 3C is a graph of the cycling performance of a Li / Ch battery with a KJCO2 positive electrode (KJCO2) at 4000 mAh g-1cycling capacity under 100 mA g-1current at -40°C. FIG. 3D is a graph of the cyclingperformance of a Li / Ch battery with a KJCO2 positive electrode (KJCO2) at 5000 mAh g-1cycling capacity under 100 mA g-1current at -40°C. FIG. 3E is a graph of chargedischarge curves of Li / Ch batteries with KJCO2 positive electrodes at cycling capacities of 1200 mAh g-1to 5000 mAh g-1under 100 mA g-1current at -40 °C. FIG. 3F shows photographs of a commercial electronic watch powered by a fully charged Li / Ch battery coin cell (CR2032) with a KJCO2 positive electrode in a -40°C freezer for 6 months. The loading of KJCCh was about 2.0 mg cm-2in all batteries in FIGS. 3A-3F.

[0015] FIGS. 4A-4G are directed to the cycling characteristics of Li / Ch batteries with KJCCh positive electrodes at -80°C. FIG. 4A is a graph of the cycling performance of a Li / Ch battery with a KJCCh positive electrode with 1200 mAh g-1cycling capacity under 25 mA g-1current at -80°C. FIG. 4B is a graph of the cycling performance of a Li / Ch battery with a KJCCh positive electrode with 2500 mAh g-1cycling capacity under 25 mA g-1current at -80°C. FIG. 4C is a graph of the cycling performance of a Li / Ch battery with a KJCCh positive electrode with 4000 mAh g-1cycling capacity under 25 mA g-1current at -80°C. FIG. 4D is a graph of charge-discharge curves of Li / Ch batteries with KJCCh positive electrodes with 1200 mAh g-1to about 5000 mAh g-1cycling capacities under 25 mA g-1current at -80°C. FIG. 4E is a photograph of the -80°C freezer and battery testers used for low temperature battery electrochemical measurements. FIG. 4F shows photographs of 1.0 M AlCh-based SOCh electrolyte used for low temperature Li / Ch batteries with KJCCh positive electrodes after being frozen in a -80°C freezer overnight. FIG. 4G is a photograph of an LED illuminated with a -80°C Li / Ch battery coin cell (CR2032) with a KJCCh positive electrode. The lighted LED outside the -80°C freezer was connected by wires to the battery inside the -80°C freezer. The loading of KJCCh was about 2.0 mg cm-2in all batteries in FIGS. 4A-4G.

[0016] FIGS. 5A-5E are directed to battery reactions on the positive electrode during cycling. FIG. 5A is a schematic drawing of the LiCl oxidation / Ch reduction in KJCCh during charge and discharge, based on reversible LiCl / Ch redox reactions. FIG. 5B is a graph of mass spectrometry detected pressure vs. vacuum pumping times of Ar, Ch, and SOCh evolved from a KJCO2 electrode charged to 5000 mAh g-1and those evolved from a discharged cell. Both cells were cycled at -40°C and stopped to remove the positive electrodes for measurements. FIG. 5C is a graph of mass spectrometry after 17.5 hours ofvacuum pumping evolved species from KJCO2 electrodes charged to 1200 mAh g-1or 5000 mAh g-1and from discharged KJCO2 electrodes. Ar (m / z = 40 amu), Ch (m / z = 70 amu), SOCI2 (m / z = 118 amu). The inset in FIG. 5C shows Ch with isotopes resolved. FIG. 5D shows 3D distributions (analysis area: 50 x 50 pm2) of C, LiCl, Ch, SCI2, S2CI2 / SO2CI2 and SOCI2 secondary ion fragments constructed from TOF-SIMS depth scans of a charged 5000 mAh g-1KJCO2 electrode evolved from -40°C Li / Ch batteries with KJCO2 positive electrodes. FIG. 5E shows 3D distributions (analysis area: 50 x 50 pm2) of C, LiCl, Ch, SCI2, S2CI2 / SO2CI2 and SOCI2 secondary ion fragments constructed from TOF-SIMS depth scans of fully discharged KJCO2 electrode from a Li / Ch battery with a KJCO2 positive electrode cycled at -40°C.

[0017] FIGS. 6A-6F are directed to battery reactions on the positive electrode and negative electrode. FIG. 6A shows X-ray photoelectron spectroscopy (XPS) spectra of Cl 2p peaks in KJCO2 electrodes after the -40°C Li / Ch battery with a KJCO2 positive electrode was charged to 1200 mAh g-1, 2500 mAh g-1, or 5000 mAh g-1. The Ch / C-Cl components of the Cl 2p peak increased with increased capacity, due to increased Ch generated and trapped in KJCO2. FIG. 6B is a graph of percentages of Ch / C-Cl and LiCl species detected in charged KJCO2 to different capacities analyzed from XPS fitting spectra in FIG. 6A. Increased charging led to clear decreases of LiCl and increases of Ch in KJCO2. FIG. 6C is a graph of the Cl 2p peak in an XPS spectrum of the charged 5000 mAh g-1KJCO2 electrode after pumping in vacuum for about 50 hours, showing much reduced Ch / C-Cl species, suggesting removal of trapped Ch in KJCO2. FIG. 6D shows graphs of high-resolution XPS spectra for Li Is (left), F Is (middle), and S 2p (right) peaks of the Li metal surface in a -40°C Li / Ch battery with a KJCO2 positive electrode after 10 cycles. FIGs. 6E-6F show cross-sectional SEM images of Li metal negative electrodes in a Li / Ch battery with a KJCO2 positive electrode after 10 cycles at room temperature (FIG. 6E) and -40°C (FIG. 6F) with 100 mA g-1current.

[0018] FIG. 7 is a graph of the first discharge curves of room temperature Li / Ch battery with a KJCO2 positive electrode using SOCh electrolyte with 1.0 M and 4.0 M AlCh.

[0019] FIG. 8 is a graph of the first discharge curves of room temperature Li / Ch batteries with positive electrodes with HCS (hollow carbon sphere), activated or not, using anelectrolyte with 1.0 M AlCh and 0.95 M LiCl dissolved in SOCh with 0.05 M of LiFSI additive.

[0020] FIGS. 9A-9B are directed to battery cycling performance of a Li / Ch battery with a KJCO2 positive electrode at -40°C using KJ without CO2 activation. FIG. 9A is a graph of the first discharge curve of the -40°C Li / Ch battery using KJ with 50 mA g'1current. FIG. 9B is a graph of cycling performance of the -40°C Li / Ch battery using KJ at 1200 mAh g-1cycling capacity with 100 mA g-1current.

[0021] FIGS. 10A-10B are directed to battery cycling performance of a battery with an amorphous carbon nanosphere (aCNS) positive electrode. FIG. 10A is a graph of the first discharge curve of the -40°C Li / Ch battery using aCNS with 50 mA g-1current.FIG. 10B is a graph of cycling performance of the -40°C Li / Ch battery using aCNS at 1200 mAh g-1cycling capacity with 100 mA g-1current.

[0022] FIGS. 11A-11B are directed to battery cycling performance of a battery with a few wall carbon nanotube (FWCNT) positive electrode. FIG. 11A is a graph of the first discharge curve of the -40°C Li / Ch battery using FWCNT after 1000°C CO2 activation with 50 mA g-1current. FIG. 1 IB is a graph of cycling performance of the -40°C Li / Ch battery using FWCNT at 1200 mAh g-1cycling capacity with 100 mA g-1current.

[0023] FIGS. 12A-12B are directed to battery cycling performance at -40°C where the battery electrolyte includes or does not include 0.05M LiFSI additive. FIG. 12A is a graph of cycling performance of -40°C Li / Ch batteries with KJCO2 positive electrodes with or without 0.05 M LiFSI additive at 1200 mAh g-1cycling capacity with 100 mA g-1current. FIG. 12B is a graph of charge-discharge curves of -40°C Li / Ch batteries with KJCO2 positive electrodes with or without 0.05 M LiFSI additive at 1200 mAh g-1cycling capacity with 100 mA g-1current.

[0024] FIG. 13 is a graph of the viscosity of SOCh electrolytes with 0 M, 1.0 M, 1.8 M, or 4.0 M AlCh as measured at room temperature.

[0025] Additional aspects and / or embodiments of the invention will be provided, without limitation, in the detailed description of the present technology set forth below. Thefollowing detailed description is exemplary and explanatory, but it is not intended to be limiting.DETAILED DESCRIPTION

[0026] Various embodiments are described hereinafter. It should be noted that the specific embodiments are not intended as an exhaustive description or as a limitation to the broader aspects discussed herein. One aspect described in conjunction with a particular embodiment is not necessarily limited to that embodiment and can be practiced with any other embodiment(s).

[0027] As used herein, “about” will be understood by persons of ordinary skill in the art and will vary to some extent depending upon the context in which it is used. If there are uses of the term which are not clear to persons of ordinary skill in the art, given the context in which it is used, “about” will mean up to plus or minus 10% of the particular term.

[0028] As used herein, “room temperature” will be understood by persons of ordinary skill in the art as a temperature of about 18°C to about 28°C.

[0029] The use of the terms “a” and “an” and “the” and similar referents in the context of describing the elements (especially in the context of the following claims) are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the embodiments and does not pose a limitation on the scope of the claims unless otherwise stated. No language in the specification should be construed as indicating any non-claimed element as essential.

[0030] Disclosed herein are Li / Ch batteries that deliver high reversible capacity (e.g., about 1200 mAh g-1to 5000 mAh g-1) at low temperatures of -85°C to about -20°C, about -85°C to about -35°C, or about -80°C to about -40°C. The batteries include a lithium metal negative electrode, a carbonaceous positive electrode having a high surface area, and a starting electrolyte that includes aluminum chloride (AlCh) in a concentration of about 0.5 M to about 1.2 M or about 0.8 M to about 1.2 M in thionyl chloride (SOCh). Through battery cycling, the electrolyte evolves to contain lithium chloride (LiCl) and various sulfur and chlorine species that support reduction / oxidation (“redox”) reactions at the negative electrode (Li / Li+) and the positive electrode (chloride / chlorine, C17Ch). The electrolyte may include fluoride-based additives (also referred to hereafter as “fluorinated electrolyte compounds”) to help form a solid-electrolyte interface (“SEI”) on the lithium negative electrode. The electrolyte has a low viscosity and high ionic conductivity at low temperatures (e.g., ionic conductivity greater than 5 mS cm'1at -80°C) and facilitates stable passivation of the Li metal negative electrode with an SEI rich in LiCl and / or LiF.

[0031] In one aspect, the present technology provides primary and secondary batteries that include negative electrodes that include lithium, positive electrodes that include carbonaceous material, separators disposed between the negative electrode and positive electrode, and electrolytes including a metal halide in a concentration of about 0.5 M to about 2.5 M in thionyl chloride. The electrolyte may also include a fluoride-based additive.Electrolytes

[0032] The starting electrolyte includes thionyl chloride and a metal halide salt dissolved in the thionyl chloride. Illustrative metal halides include, but are not limited to, AlCh, NaCl, LiCl, GaCh, or a mixture of any two or more thereof. The concentration of the metal halide may be about 0.5 M to about 2.5 M (e.g., 0.5 M, 0.6 M, 0.7 M, 0.8 M, 0.9 M, 1.0 M, 1.1 M, 1.2 M, 1.3 M, 1.4 M, 1.5 M, 1.6 M, 1.7 M, 1.8 M, 1.9 M, 2.0 M, 2.1 M, 2.2 M, 2.3 M, 2.4 M, 2.5 M, or any value therebetween. For example, the metal halide may include aluminum chloride present in a concentration of about 0.5 M to about 1.2 M, or about 0.8 M to about 1.2 M (e.g., 0.8 M, 0.9 M, 1.0 M, 1.1 M, 1.2 M, or any value therebetween), or about 0.9 M to about 1.1 M. Alternatively or in addition to the aluminum chloride, the metal halide in the electrolyte may include lithium chloride presentin a concentration of about 0.7 M to 1.2 M (e.g, 0.7 M, 0.8 M, 0.9 M, 1.0 M, 1.1 M, 1.2 M, or any value therebetween).

[0033] The starting electrolyte may also include a fluorinated electrolyte compound present in a small concentration (e.g., 0.01 M to 0.10 M). For example, the fluorinated electrolyte compound may be present in a concentration of about 0.02M to about 0.08 M. As another example, the fluorinated electrolyte compound may be present in a concentration of about 0.01 M, 0.02 M, 0.03 M, 0.04 M, 0.05 M, 0.06 M, 0.07 M, 0.08 M, 0.09 M, 0.1 M, or any value therebetween. Illustrative fluorinated electrolytes include an ammonium, alkyl ammonium, or alkali metal salt of a fluorinated sulfonamide such as but not limited to a bis(fluorosulfonyl)imide or bis(trifluoromethane)sulfonimide, or oxalatoborates such as but not limited to bis(oxalate)borate or a dihalo(oxalato)b orate, or a combination of any two or more thereof. Specific examples include, but are not limited to lithium bis(fluorosulfonyl)imide, sodium bis(fluorosulfonyl)imide, an ammonium or alkyl ammonium bis(fluorosulfonyl)imide, lithium bis(trifluoromethane)sulfonimide, sodium bis(trifluoromethane)sulfonimide, an ammonium or alkyl ammonium bis(trifluoromethane)sulfonimide, lithium bis(oxalate)borate, sodium bis(oxalate)borate, lithium difluoro(oxalato)borate, lithium difluoro(oxalato)borate, or a combination of any two or more thereof.

[0034] The electrolyte may be a liquid at a low temperature of -85°C to about -20°C, about -85°C to about -35°C, or about -85°C to about -40°C. The difference in viscosity of the electrolyte at these low temperatures as compared to the electrolyte’s viscosity at room temperature may be small (z.e., the viscosities at low temperature and room temperature are similar). For example, the viscosity of the electrolyte at low temperature may be up to about three times higher (e.g. p to about 2.5 times higher, up to about 2 times higher, or up to about 1.5 times higher) than the viscosity of the electrolyte at room temperature.Positive Electrode Materials

[0035] The positive electrode includes a carbonaceous material. Illustrative carbonaceous materials include, but are not limited to, KETJENBLACK® (KJ), amorphous carbon nanospheres (aCNS), carbon nanotubes, few-walled carbon nanotubes (FWCNT),acetylene black (AB), graphene, nanographene, graphene oxide, reduced graphene oxide, carbon foam, carbon fibers, graphite particles, nano-graphite particles, or a mixture of any two or more thereof. In some embodiments, the positive electrode includes a carbonaceous material prepared by heat-treating the carbonaceous material in CO2 gas, N2 gas, water vapor, low concentrations of oxygen, or a combination of any two or more thereof. In some embodiments, the positive electrode includes a carbonaceous material prepared by heat-treating the carbonaceous material in CO2 gas, N2 gas, O2 gas, or water vapor. The heat-treating may be conducted at a temperature of at least 500°C. In some embodiments, the heat-treating is conducted at a temperature of at least 600°C, 700°C, 800°C, 900°C, 1000°C, or 1100°C, or from about 500°C to about 1500C, from about 500°C to about 1100°C, from about 600°C to about 1500°C, from about 600°C to about 1100°C, from about 700°C to about 1500°C, from about 700°C to about 1100°C, from about 800°C to about 1500°C, from about 800°C to about 1100°C, from about 900°C to about 1500°C, from about 900°C to about 1100°C, from about 1000°C to about 1500°C, or from about 1000°C to about 1100°C.

[0036] KETJENBLACK® (KJ) may be KJ EC-600JD. KETJENBLACK® materials are conductive carbon blacks made with a furnace process, where carbon-containing materials undergo an incomplete combustion. KJ EC-600JD may be in the form of particles having a diameter of about 30 nm to about 50 nm, aggregates of about 100 nm to about 1000 nm, and / or agglomerates of about 50 pm to about 5 mm. BET surface area for KETJENBLACK® EC-600JD is about 1200 m2g’1tol300 m2g’1. KJ EC-600JD has an intrinsic resistivity of about 0.01 - 0.1 [Q cm],

[0037] In any embodiment, the carbonaceous materials have a high surface area (e.g., 1000-4000 m2 / g, 2000-3000 m2 / g, or 2300-2500 m2 / g) and / or a high porosity (e.g., at least 5, 5.5, 6, 6.5, or 7 cm3g-1; or up to about 6 cm3g-1or up to about 7 cm3g-1). For example, the pore volume may be about 2 cm3g'1to about 6 cm3g'1, about 2 cm3g'1to about 7 cm3g'1, 3 cm3g'1to about 10 cm3g'1, about 5 cm3g'1to about 8 cm3g'1, about 6 cm3g-1to about 7 cm3g-1, about 6.5 cm3g-1to about 7 cm3g-1, about 6.5 cm3g-1to about 7 cm3g-1, about 6.4 cm3g-1to about 7 cm3g-1, about 6.3 cm3g-1to about 7 cm3g-1, about 6.2 cm3g-1to about 7 cm3g-1, or about 6.1 cm3g'1to about 7 cm3g-1. As utilized herein with respect to the carbonaceous materials, the terms “micropore” or“microporosity,” and similar referents are referring to the part of the pore space that has a characteristic dimension less than 2 nm. The terms “mesopore” or “mesoporosity,” and similar referents are referring to the part of the pore space that has a characteristic dimension larger than 2 nm but less than 50 nm. The terms “macropore” or “macroporosity,” and similar referents are referring to the part of the pore space that has a characteristic dimension larger than 50 nm. In some embodiments, the carbonaceous materials in the positive electrode primarily include mesopores. In some embodiments, the carbonaceous materials include micropores and mesopores. In some embodiments, the carbonaceous materials include micropores, mesopores, and macroporous. The mesoporous volume may be about 3 cm3g'1to about 10 cm3g'1, about 5 cm3g'1to about 8 cm3g'1, about 6 cm3g-1to about 7 cm3g-1, about 6.5 cm3g-1to about 7 cm3g-1, about 6.4 cm3g-1to about 7 cm3g-1, about 6.3 cm3g-1to about 7 cm3g-1, about 6.2 cm3g-1to about 7 cm3g-1, or about 6.1 cm3g'1to about 7 cm3g-1. In some embodiments, the mesoporous volume may be up to about 7 cm3g'1(e.g., about 0.1 cm3g'1toa bout 7 cm3g"3). In some embodiments, the positive electrode includes carbonaceous materials having a high microporosity (e.g., at least 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07 0.08, 0.09, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, or 1.5 cm3 / g).

[0038] The carbonaceous material may be disposed on a conductive substrate. The conductive substrate may be a metal. For example, the conductive substrate may be nickel or stainless steel. The form of the conductive substrate may be a solid foam, a solid foil, a solid mesh, a carbon fiber, a carbon paper, or any other suitable form. The carbonaceous material may be disposed on the conductive substrate with or without a binder. Illustrative binders include, but are not limited to, polyvinylidene difluoride (PVDF), polyvinyl alcohol (PVA), polyethylene, polystyrene, polyethylene oxide, polytetrafluoroethylene (Teflon), polyacrylonitrile, polyimide, styrene butadiene rubber (SBR), carboxy methyl cellulose (CMC), alginate, gelatin, a copolymer of any two or more such polymers, or a blend of any two or more such polymers.

[0039] As the Li / Ch battery cycles, additional materials may be incorporated into the positive electrode. For example, lithium chloride (LiCl) may be deposited on the surface and / or in the pores of the carbonaceous material. Other species, including SOCh, Ch, SCh, S2CI2, and / or SO2CI2 may be deposited on the carbonaceous material. These speciesmay be deposited within pores of the conductive carbon material. Ch may accumulate within the pores of the carbonaceous material.Negative Electrode Materials

[0040] The negative electrode includes metallic lithium. In any embodiment, the negative electrode may further include silicon, silicon oxides, or carbon materials including, but not limited to, synthetic graphite, natural graphite, amorphous carbon, hard carbon, soft carbon, acetylene black, mesocarbon microbeads (MCMB), carbon black, Ketjen® black, mesoporous carbon, porous carbon matrix, carbon nanotube, carbon nanofiber, or graphene.Other Battery Components

[0041] The positive electrode and / or negative electrode may also include a current collector. Current collectors may include those of nickel, copper, stainless steel, titanium, tantalum, platinum, gold, aluminum, nickel, cobalt nickel alloy, highly alloyed ferritic stainless steel containing molybdenum and chromium, or nickel-, chromium-, or molybdenum-containing alloys. The current collector may be a solid foil, a solid foam, or a solid mesh.

[0042] A separator may be disposed between the positive electrode and negative electrode. Illustrative separators may include one or more of a glass fiber paper, a quartz fiber paper, a porous glass membrane, a porous glass filter, a porous quartz membrane, a porous quartz filter, a porous PTFE membrane, or a combination of any two or more thereof.Method of Cycling a Li / Ch Battery

[0043] In another aspect, a process is provided for cycling a Li / Ch battery at low temperatures of about -85°C to about -20°C, about -85°C to about -35°C, about -85°C to about -40°C, about -85°C to about -75°C, or about -45°C to about -55°C. For example, the battery may be cycled at -20°C, -30°C, -40°C, -50°C, -60°C, -70°C, or -80°C, or any values therebetween.

[0044] Cycling the battery at these low temperatures may deliver a specific capacity of about 1000 mAh g-1to about 5000 mAh g-1(e.g., at least 1100 mAh g-1, 1200 mAh g-1, 1300 mAh g-1, 1400 mAh g-1, 1500 mAh g-1, 1600 mAh g-1, 1700 mAh g-1, 1800 mAh g’1, 1900 mAh g’1, 2000 mAh g’1, 2100 mAh g’1, 2200 mAh g’1, 2300 mAh g’1, 2400 mAh g-1, or 2500 mAh g-1, 3000 mAh g-1, 4000 mAh g-1, or 5000 mAh g-1). The battery may deliver this capacity over at least 50 to 200 electrochemical cycles (e.g., at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 150, or 200 cycles). For example, the battery may deliver a specific capacity of about 1100 mAh g-1to about 1200 mAh g-1over at least 70 electrochemical cycles at about -75°C to about -85°C. As another example, the battery may deliver a specific capacity of about 2400 mAh g-1to about 2500 mAh g-1over at least 70 electrochemical cycles at about -35°C to about -45°C. As another example, the battery may deliver a specific capacity of about 1100 mAh g-1to about 1200 mAh g-1over at least 100 electrochemical cycles at about -35°C to about -45°C.Method of Manufacturing a Li / Ch Battery

[0045] In another aspect, a method of manufacturing a Li / Ch battery configured for operation at low temperatures is disclosed. The method includes assembling a Li / Ch battery including a positive electrode, a negative electrode, a separator therebetween, and an electrolyte, where the positive electrode, negative electrode, separator, and electrolyte may be any of those described above. The method may further include preparing the positive electrode and / or activating the carbonaceous material in the positive electrode prior to assembling the battery. The method may further include preparing the electrolyte.

[0046] The electrolyte may be prepared by mixing one or more metal halides in the desired concentration in SOCh.

[0047] The battery may be assembled by preparing the positive electrode. The positive electrode may be prepared by disposed a carbonaceous material, activated or not activated, on a conductive foam or foil.

[0048] The activated positive electrode carbonaceous material may be prepared by heat- treating the carbonaceous material in CO2 gas, N2 gas, water vapor, low concentrations of oxygen, or a combination of any two or more thereof. In some embodiments, the positive electrode includes a carbonaceous material prepared by heat-treating the carbonaceousmaterial in CO2 gas. The heat-treating may be conducted at a temperature of at least 500°C. In some embodiments, the heat-treating is conducted at a temperature of at least 600°C, 700°C, 800°C, 900°C, 1000°C, or 1100°C, or from about 500°C to about 1500C, from about 500°C to about 1100°C, from about 600°C to about 1500°C, from about 600°C to about 1100°C, from about 700°C to about 1500°C, from about 700°C to about 1100°C, from about 800°C to about 1500°C, from about 800°C to about 1100°C, from about 900°C to about 1500°C, from about 900°C to about 1100°C, from about 1000°C to about 1500°C, or from about 1000°C to about 1100°C.

[0049] The positive electrode may be prepared by disposing the carbonaceous material on a nickel or stainless steel material having the form of foam or foil. The carbonaceous material may be disposed on the foam or foil by adding a slurry of carbonaceous material onto the foam or foil and allowing the slurry solvent to evaporate. The positive electrode may be dried at a temperature of about 70°C to about 120°C for 2 hours to 36 hours. The dried positive electrode may be pressed with a roller prior to battery assembly.

[0050] The negative electrode may be prepared disposing a lithium metal material (e.g., a foil) on a current collector. In some embodiments, the lithium metal may be prepared by removing surface contamination.

[0051] The components of the battery may be assembled in an inert environment. For example, the battery may be assembled in a glove box filled with argon gas. The components may be assembled by disposing the negative electrode and positive electrode on either side of the battery separator. The battery may further include current collectors on the negative electrode and / or positive electrode side. The electrolyte is added to the battery in a desired volume. After assembly, the battery is sealed against air infiltration.

[0052] The present invention, thus generally described, will be understood more readily by reference to the following examples, which are provided by way of illustration and are not intended to be limiting of the present invention.EXAMPLES

[0053] The following materials and methods were used in Examples 1-7, unless otherwise specified.Carbon Activation

[0054] The KJCO2 was synthesized by annealing KJ using a horizontal tube furnace in an environment of flowing CO2 at a flow rate of about 200 cc min-1. The annealing temperature was 1000°C and the annealing time was 40 minutes. The temperature was increased from room temperature to 1000°C at a rate of 10°C min-1. After annealing, the system was allowed to cool down naturally. About 85% mass loss was recorded after annealing with the remaining carbon being activated KJ (KJCO2).Electrolyte

[0055] Unless otherwise specified, the electrolyte used in Examples 1-7, was 1.0 M AlCh, 0.95 M LiCl, and 0.05 M LiFSI in SOCI2. The electrolyte was prepared by adding 1.0 M AlCh to SOCI2. After the AlCh had completely dissolved, 0.05 M LiFSI was then added into the solution. The mixture was then stirred until the LiFSI was dissolved. 0.95 M of LiCl was then added into the solution and stirred for about 30 minutes or until LiCl could no longer be dissolved. Note that a little excess of LiCl was normally added into the solution in this step to make sure that the electrolyte was completely neutralized. After stirring, a small amount of residual LiCl remained in the solution. The supernatant was used as the electrolyte.Battery Assembly and Electrochemical Measurement

[0056] 90% by weight of either KJ or KJCO2 powder and 10% by weight of PTFE (60% aqueous dispersion) were mixed in 100% ethanol to form a positive electrode solution. The mixture was then sonicated for 2 hours. Nickel (Ni) foam substrates were cut into circular pieces with a diameter of 1.5 cm using a disk cutter. The Ni foams were sonicated in 100% ethanol for 15 minutes and then dried at 80°C until the ethanol evaporated. The Ni foam substrates were then hovered over a hot plate using a grill, and the mixture of KJ or KJCO2, PTFE, and ethanol was then slowly dropped (180 pL each time) onto these Ni foam substrates. The solvent from each droplet of positive electrode solution was completely dried before another droplet was added to the Ni foam. The two carbon mass loadings were about 2 mg cm'2and about 6 mg cm'2. The prepared electrodes were then dried at 80°C overnight and pressed using a roller before being used as positive electrodes (cathodes) in batteries.

[0057] All batteries were made inside an argon-filled glovebox. A nail file was used to scratch the Li metal to remove surface contamination. The scratched Li metal was then applied onto a coin cell spacer before being used as the negative electrode (also called an anode).

[0058] The Li batteries were assembled in the argon-filled glovebox with KJ or KJCCh positive electrodes, 2 layers of quartz fiber filters, Li negative electrodes, and a piece of coin cell spring was put in the center of a CR2032 coin cell positive case, with 150 pL of electrolyte added onto the separators. The CR2032 negative electrode case was put on top and the entire battery was sealed using a digital pressure controlled electric crimper. After the coin cell was assembled, a layer of silicone sealant was applied on the coin cell to cover the O-ring to further prevent water and air from leaking into the battery.

[0059] The battery was operated using a battery tester. The low temperature electrochemical measurements of batteries were tested using a -20°C freezer, -40°C freezer, and -80°C freezer. The charging step in battery testing was controlled by setting the charging time depending on the cycling capacity (mAh g-1) and current (mA g'1), where charging time was the cycling capacity divided by the current. The discharging step was controlled by setting a discharge cut-off voltage of 2 V. For the batteries tested at room temperature, -20°C, and -40°C, the first discharge and cycling current density was 50 mA g'1or 100 mA g'1, based on the carbon mass. For the batteries tested at -80°C, the first discharging and cycling current density was 12.5 mA g-1, and 25 mA g-1respectively.Characterization

[0060] The morphologies of the samples were characterized using field-emission scanning electron microscopy (SEM) at an accelerating voltage of 15 kV and emission current of 10 pA. In order to obtain the best characterization of pristine KJ and KJCCh, it was necessary to remove the moisture at 100 °C before characterization. For the cycled KJCCh electrodes and Li metal electrodes, samples were taped to the SEM sample stage using double-sided carbon adhesive in an argon-filled glovebox, and the electrodes were firmly fixed to prevent magnetic attraction. When transferring the sample stage to the SEM exchange chamber, air exposure was limited to avoid oxidation of the samples.

[0061] Raman spectra was measured using an Ar+laser of 532 nm. Before each measurement, a piece of p-type boron doped silicon wafer was used for calibration and the silicon peak was adjusted to 520.7 cm-1.

[0062] XRD measurements were conducted. For the cycled KJCO2 electrodes, the batteries were disassembled and the KJCO2 electrodes were taken out from the batteries in an argon-filled glovebox. The KJCO2 electrodes were sealed inside a designed XRD holder that consisted of a polycarbonate dome and an O-ringed 1-inch Si (311) holder in glovebox without exposure to air. The sample was then measured at a scan rate of 2° min"1.

[0063] The Brunauer-Emmett-Teller (BET) surface area and pore volume of pristine KJ and KJCO2 were measured. Before each measurement, the appropriate amount of carbon was weighed and degassed at 350°C. After degassing, the weight of the carbon was measured again for final surface area and porosity analysis.

[0064] The ionic conductivity of electrolytes was acquired at different temperatures. Before measurement, the ionic conductivity sensor was calibrated. The sensor was placed in the electrolytes at room temperature or in freezers.

[0065] The viscosity determination was measured by a Ubbelohde viscometer. Viscosity measurement of SOCI2 at room temperature served as control group (qo) for comparison with electrolyte solutions of 1.0, 1.8, and 4.0 M AlCh dissolved in SOCI2. The ratios between the recorded time for solution movement through the viscometer and for pure SOCI2 (T|O)wasused as an indicator of the viscosity changes of electrolyte. For the viscosity determination of 1.0 M AlCh-based electrolyte at different temperatures, the 1.0 M AlCh-based electrolyte at room temperature was first measured and set as control group (qo), then the electrolyte was moved to freezers for low temperature viscosity measurements.

[0066] The electrochemical impedance spectroscopy (EIS) of batteries were measured using a potentiostat / galvanostat. The working electrode was connected to the KJCO2 positive electrode, and the counter and reference electrodes were connected to the Li negative electrode. The initial voltage of the measurement was set to be the open-circuit potential of the battery at the time of the measurement. The high frequency was1 x IO5Hz, and the low frequency was 0.01 Hz. The amplitude of the measurement was 0.005 V.

[0067] Time-of-flight secondary-ion mass spectrometry (TOF-SIMS) measurements were conducted. To acquire the 3D distribution secondary ion fragments imaging and depth profiles of KJCO2 electrodes in FIGS. 5D and 5E, after the Li / Ch battery with a KJCO2 positive electrode had cycled to a charged or discharged state, respectively, the batteries were disassembled inside the argon-filled glovebox, and the KJCO2 electrode was removed from the battery for testing. Air exposure was reduced to the extent possible. The pressure of the analysis chamber was below 1.1 x IO-9mbar. The depth profiling analysis (anion mode) was performed with a Bi3+primary ion beam (scanning area 50 x 50 pm2, pixel 128 x 128), with 30 keV energy, 0.48 pA beam current, and 45° angle. The sputtering ion beam was Cs, with 2 keV energy and 45° angle, and the sputtering area was 200 x 200 pm2. After depth sputtering and scanning, the 3D distribution secondary ion fragments imaging was reconstructed.

[0068] Mass spectrometry measurements were conducted. After the battery was cycled to its designated state, the KJCO2 electrodes were removed from the batteries in an argon- filled glovebox for measurement. The electrodes were not exposed to air prior to measurement.

[0069] XPS measurements were conducted on cycled electrodes. Electrodes were not exposed to air prior to measurement. After electrodes were loaded into the instrument, the instrument was degassed for about 2 hours prior to measurement. All the XPS data was calibrated by C Is 284.8 eV and analyzed and fitted using Casa XPS.EXAMPLE 1: First Discharge of Li / Ch Batteries with KJCO2 Positive Electrodes

[0070] CR2032 coin cell (20 mm diameter by 3.2 mm thickness) batteries were constructed with Li metal as the negative electrode. Battery positive electrodes were either KJ, forming Li / Ch batteries with untreated KJ positive electrodes, or KJCO2, forming Li / Ch batteries with KJCO2 positive electrodes. The electrolyte used in all batteries was 1.0 M AlCh + 0.95 M LiCl dissolved in SOCh with 0.05 M of LiFSI additive, prepared according to the method above, unless otherwise specified. The as-received KJ material (FIG. IB) showed signs of etching and apparent reduction in size after activation in CO2 at 1000°C for 45 minutes according to the method above (FIG. 1C), accompanied by a mass loss of about 85% due to the reaction:CO2 (g) + C (s) -2 CO (g).

[0071] Raman spectroscopy indicated increased defects and disorder in KJCO2, and a complete disappearance of graphitic ordering in X-ray diffraction (XRD) measurements of in KJCO2.

[0072] At room temperature, the Li / Ch battery with a KJCO2 positive electrode showed a 2 -times higher first discharge capacity than the battery with an untreated KJ positive electrode. The first discharge capacity of the Li / Ch battery with an untreated KJ positive electrode was about 15,300 mAh g-1the first discharge capacity of the Li / Ch battery with a KJCO2 positive electrode was about 29,100 mAh g-1, as calculated using carbon mass loading values of about 2 mg cm-2(FIG. ID). The first discharge used a current of 50 mA g-1, and about 3.55 V discharge voltage. A higher KJCO2 mass loading of about 6 mg cm-2afforded an impressive first discharge capacity of about 9,407 mAh g-1. Li metal oxidation to Li+on the negative electrode and the SOCh reduction to sulfur (S), sulfur dioxide (SO2) and LiCl deposited on the porous carbon positive electrode according to the reaction2 SOCh + 4 Li++ 4 e" S + SO2 + 4 LiCl, may contribute to the high first discharge capacity.

[0073] The CO2 activation process of KJ to KJCO2 increased the specific surface area from 1307.4 m2g-1to 2386.9 m2g-1and pore volume from 3.1 cm3g-1to 6.5 cm3g-1(FIG. IE), allowing for increased deposition of LiCl and higher discharge capacity (FIG. ID) The high surface area and large pore volume of the carbon materials may also contribute to the reversibility of the specific capacity of secondary batteries.

[0074] At low temperatures of -20°C, -40°C, and -80°C, the Li / Ch battery with a KJCO2 positive electrode delivered a first discharge voltage and capacity of 3.4 V and8,521 mAh g-1at -20°C; 3.3 V and 5,532 mAh g-1at -40°C; and 3.1 V and4,503 mAh g-1at -80°C (FIG. 2A). LiCl deposition on KJCO2 was confirmed by XRD (FIG. 2B), both in the pores of KJCO2 and on the surfaces of KJCO2 until passivation (FIG. 2C). Based on the SOCI2 reduction reaction equation and the first discharge capacity, the estimated deposited LiCl volume was about 0.07 cm3, about 0.027 cm3, about 0.013 cm3, and about 0.011 cm3at room temperature, -20°C, -40°C, and -80°C, respectively, as compared to the total pore volume of about 0.023 cm3in the KJCO2 electrode (based on pristine KJCO2 weight and pore volume).

[0075] LiCl deposition on KJCO2 decreased with reduced discharge capacity at lower temperatures (FIG. 2A) due to increased electrolyte viscosity, decreased Li+and Cl" ion diffusion, and lower electrolyte conductivity. The electrolyte conductivity decreased from 20.34 mS cm-1at room temperature to 5.26 mS cm-1at -80°C (FIG. 2D). SEM imaging revealed slower LiCl deposition kinetics with the size of deposited LiCl crystals reduced from greater than 3 pm at room temperature (FIG. 2E) to about 1.5 pm, about 200 nm, and about 60 nm at -20°C, -40°C, and -80°C, respectively, (FIGS. 2F-2H), accompanied by smaller LiCl XRD peaks for batteries cycled at -40°C as compared to room temperature (FIG. 2B).

[0076] The electrolyte with 1 M A1CL and the low melting point (-104.5 °C) of SOCI2 contributed to battery operation at low temperatures of -20°C to -80°C. This electrolyte exhibited low electrolyte viscosity as compared to those in conventional Li / Ch batteries with higher A1CL concentrations of about 4 M or 1.8 M (FIG. 13). Through CO2 activation of a carbon black material and an electrolyte with 1 M A1CL, a first discharge capacity of about 30,000 mAh g-1with flat discharge plateau of about 3.55 V was obtained.

[0077] Consistent with the viscosity results, batteries with electrolytes having higher A1CL concentrations resulted in lower first discharge curves than electrolytes having 1.0 M A1CL. FIG. 7 is a graph of the first discharge curves of room temperature Li / Ch batteries with KJCO2 positive electrodes using SOCh electrolyte with 1.0 M or 4.0 M AlCh. The first discharge capacity of the battery with the 1.0 M AlCh electrolyte was 29,100 mAh g-1. In contrast, the battery with the electrolyte with 4.0 M AlCh showed a drastically lower first discharge capacity of 8463 mAh g-1. These results indicate thatelectrolytes with 1.0 M AlCh exhibit better cycling performance that electrolytes with 4.0 M AlCh for Li / Ch batteries.EXAMPLE 2: Secondary Batteries Operating at Low Temperatures of -20 °C, -40 °C, and -80 °C

[0078] In the temperature range of room temperature to -20°C, after the first discharge the Li / Ch battery with a KJCO2 positive electrode was rechargeable and cyclable at a specific capacity of 1200 mAh g-1and an areal capacity of about 2.4 mAh cm-2, under a current of 100 mA g-1, with a cycle-life of about 70. Rechargeability may have resulted from reversible LiCl / Ch redox reactions on the positive electrode. Specifically, Ch was generated by LiCl oxidation during charging and trapped in the pores of KJCO2, and reduced to LiCl upon discharge. Note that throughout this work, charging was controlled by setting the charging time at a specific capacity and discharge proceeded down to a cutoff voltage of 2.0 V.

[0079] At -40°C, the Li / Ch battery with a KJCO2 positive electrode exhibited improved cycle life over about 130 cycles with a specific capacity of 1200 mAh g-1under a current of 100 mA g'1. The average coulombic efficiency (CE) was about 100% (FIG. 3A). Further, the battery showed cyclability at a higher specific capacity of 2500 mAh g-1and an areal capacity of about 5 mAh cm'2per cycle at -40°C over more than 75 cycles (FIG. 3B) These results were much improved over cycling at -20 °C, which was less 15 cycles at the higher specific capacity of 2500 mAh g-1. Increasing the cycling capacities to 4000 mAh g-1and (an areal capacity about 8 mAh cm'2) and 5000 mAh g-1(areal capacity about 10 mAh cm-2) exhibited rechargeability and cyclability with a reduced cycle-life of less than 10 cycles (FIGS. 3C-3D).

[0080] The Li / Ch battery with a KJCO2 positive electrode cycled at -40°C had a high cycling capacity of the 1200 mAh g-1with a lifetime of 130 cycles; and 2500 mAh g-1with a lifetime of 75 cycles. The Li / Ch battery with a KJCO2 positive electrode cycled at -40°C also exhibited a voltage discharge plateau of about 3.3 V (FIG. 3E)

[0081] The Li / Ch battery with a KJCO2 positive electrode was cycled at -40°C with a specific discharge capacity of 5000 mAh g-1. This capacity was used to power anelectronic watch operating at a voltage of 3.0 V in a -40°C freezer. The fully charged battery powered the watch at -40°C for over 6 months (FIG. 3F).

[0082] At -80 °C, the Li / Ch batteries with KJCO2 positive electrodes cycled stably at 1200 mAh g-1over about 70 cycles with nearly 100% average CE (FIG. 4A, current 25 mA g'1). Batteries were also cyclable at a higher specific capacity of 2500 mAh g-1(FIG. 4B), 4000 mAh g1(FIG. 4C) and even about 5000 mAh g but with shorter cycle lives. At -80 °C, a battery charging plateau of about 4.25 V and discharging plateau of about 3.1 V were attributed to oxidation of LiCl to Ch and the reduction of Ch back to LiCl, respectively (FIG. 4D). In addition to LiCl oxidation on KJCO2, charging to higher capacities also led to increased oxidation of SOCI2 in the electrolyte to form SCI2 / S2CI2, especially when charging to about 5000 mAh g-1during which a pronounced increase in charging voltage was observed (FIG.4D). This was also consistent with the appearance of an impressive high discharge voltage plateau at about 3.8 V, with a specific capacity up to 1000 mAh g-1(FIG. 4D) due to reduction of the SCI2 / S2CI2 generated in the charging step. The discharge plateaus at about 3.1 V and about 2.9 V corresponded to reduction of Ch and SO2CI2, respectively (FIG. 4D).

[0083] A Li / Ch battery with a KJCO2 positive electrode placed in a -80 °C freezer (FIG. 4E-4G) charged to about 5000 mAh g-1to power a light-emitting diode (LED), with an operating voltage greater than 3.0 V. FIG. 4F shows electrolyte remained as a liquid at -80 °C.EXAMPLE 3: Spectroscopic Investigation of Battery Reactions on the Positive Electrode Side

[0084] For batteries after cycling at -40 °C, SEM imaging showed the formation of LiCl with a thickness of 200 nm to 300 nm on KJCO2 corresponding to reduction of trapped Ch to LiCl. Upon charging from 1200 mAh g-1to 5000 mAh g-1, the deposited LiCl was increasingly removed / oxidized, accompanied by decreases in battery electrochemical impedance. The formation of Ch (2 LiCl —> 2 Li++ Ch + 2 e") may be a primary charging mechanism, and reduction of trapped Ch in KJCO2 to LiCl may be a primary discharging mechanism, providing the charge and discharge plateaus of 4.01 V and 3.3 V, respectively,(FIG. 3E) with an overall battery reaction of Li + 1 / 2 Ch LiCl at -40 °C, as shown in the schematic in FIG. 5A.

[0085] SEM indicated that not all of the surface LiCl coating was oxidizable to Ch for subsequent reduction and battery cycling. When cycling / charging to higher capacities (e.g., 5000 mAh g-1), LiCl in the carbon electrode was increasingly oxidized to Ch, accompanied by oxidation of SOCI2 in electrolyte on carbon sites free of salt coating to form SCI2 / S2CI2 and SO2CI2 (FIG. 3E and FIG. 4D, showing an increase in charging voltage). Without being bound by any theory, while much of the Ch was trapped in the porous carbon positive electrode for reversible reduction to LiCl during discharge, it is possible that the more reactive SCI2 / S2CI2 and SO2CI2 species may have been poorly trapped, migrated into the electrolyte and shuttled to the Li negative electrode side to cause chemical oxidation and corrosion. Such shuttling may lead to negative electrode degradation and consumption of electrolyte that prevented 100% SOCI2 regeneration and decreased battery cycling life.

[0086] Mass spectrometry was employed to probe ex situ trapped species in KJCO2 after cycling Li / Ch batteries. The positive electrodes were placed under vacuum pumping for mass / charge (m / z) sampling of gaseous species evolved from KJCO2. The detected Ch escaping from a charged KJCO2 electrode (to 5000 mAh g-1or 1200 mAh g-1) far exceeded that from a discharged KJCO2 (FIG. 5B-5C).

[0087] Charged KJCO2 (to 5000 mAh g-1at -40 °C) and discharged KJCO2 was chemically mapped in 3D using time-of-flight secondary ion mass spectroscopy (TOF- SIMS) depth profiling. The analysis area as 50 x 50 p.m2. In charged KJCO2, low counts of LiCl and high counts of Ch / SCh^Ch / SCLCh / SCh / carbon were detected due to electro-oxidation of LiCl and SOCI2 to CI2, SCI2, S2CI2 and SO2CI2 and more exposed carbon surfaces free of LiCl coating upon charging (FIG. 5D). These species reduced while LiCl and SOCI2 counts increased upon discharging (FIG. 5E), indicating LiCl formation and regeneration of SOCI2.

[0088] Ex-situ XPS was employed to probe species residing in KJCO2 after being charged to or discharged from 1200 mAh g-1, 2500 mAh g-1, and 5000 mAh g-1, respectively. In charged KJCO2, a peak was detected in the Cl 2p spectrum at about 200 eV bindingenergy (FIG. 6A) but not in discharged KJCO2. The peak at about 200 eV may be attributable to Ch remaining trapped in the KJCO2 and a small percentage of C-Cl. The Ch percentage increased with increasing charging capacity from 1200 mAh g-1to 5000 mAh g-1, accompanied by decreases in the LiCl XPS signal on KJCO2 (FIGS. 6A and 6B).

[0089] The peak at about 200 eV in the 5000 mAh g-1charged KJCO2 electrode significantly decreased (FIG. 6C) after about 50 hours vacuum pumping (over which mass spectrometry detected little Ch remaining in the electrode), indicating that Ch remained in charged carbon electrode for up to about 2 days under vacuum. Afterwards a weak peak at about 200 eV remained and was attributed to C-Cl formed by chlorination of carbon during battery charging. The C-Cl peak persisted after washing by deionized ultra-filtered (DIUF) water to remove all the residual LiCl and AlCh, but disappeared upon annealing at 600 °C in a N2 atmosphere due to C-Cl bond breaking. A peak at about 286.6 eV was observed in charged KJCO2 in the C Is spectrum, likely due to Cl bonding.EXAMPLE 4: Temperature Effects of Trapping of Reactive Species in Porous Carbon and Battery Reversibility

[0090] Cycling of Li / Ch batteries with KJCO2 positive electrodes at higher specific capacities generated larger amounts of CI2, SCI2 / S2CI2 and SO2CI2 species on the positive electrode side during charging. These species were highly reactive and may have shuttled to the Li negative electrode to damage the SEI and corrode the underlying Li metal. When such side reactions were severe, higher than 100% CE was observed suggesting that the Li / SEI layer equilibrium was broken by the shuttled species, the Li metal became more exposed, and the battery therefore discharged beyond the Li deposited on the positive electrode by charging. Li / Ch battery with the KJCO2 positive electrode cycling at 1200 mAh g-1and -40 °C (FIG. 3A) exhibited stable cycling with about 100% CE over more than 100 cycles. Under these conditions, reactive species were effectively trapped in the carbon positive electrodes with little shuttling effect. The lack of shuttling effect was corroborated with battery retention testing where a battery charged to 1200 mAh g-1at -40 °C was held at open-circuit voltage for 3 days and then discharged. The battery retained about 100% CE without any capacity loss. Retention testing was repeated several times during cycling over more than 100 cycles with similar results.

[0091] When a Li / Ch battery with a KJCO2 positive electrode was charged at -40 °C and warmed to room temperature to hold for 3 days at open circuit voltage, the main discharge plateau at about 3.3 V decreased in capacity while the lower discharge plateau at about 3.10 V was extended, accompanied by reduced battery cycle life to less than 30 cycles. The plateau at about 3.10 V plateau may be attributed to the reduction of SO2CI2 formed by reactions between SO2 and escaped CI2, due to reduced Ch trapping by KJCO2 at higher temperatures. A high CE of greater than 105 % following open circuit voltage hold may have indicated the presence of a shuttling effect.

[0092] Temperature dependent battery characteristics suggested that trapping of reactive species in the porous carbon was more effective at lower temperatures, thereby preventing shuttling and allowing higher reversible cycling capacity and about 100% regeneration of SOCI2 (consumed in the charging step) via the following reaction:LiCl + A1C14' SOC1+LiAlCh + SOCI2.

[0093] Complete trapping / retention of electro-oxidation generated species in the positive electrode may be useful for prolonging the cycle life of Li / Ch batteries.

[0094] Different than cycling at other temperatures, battery cycling at -80°C with increased charging capacity from 1200 mAh g-1to about 5000 mAh g-1led to an increase in extended high discharge voltage plateaus at about 3.8 V (well above the Ch reduction voltage plateau of about 3.1 V, FIG. 4D), suggesting efficient trapping and reduction of SCI2 / S2CI2 generated in the charging step at -80 °C. The 3.8 V discharge plateau was very small in batteries operated at -40°C (1200 mAh g-1to 5000 mAh g-1, FIG. 3E), suggesting escape of SCI2 / S2CI2 species from the positive electrodes without subsequent electro-reduction during discharging.

[0095] Taken together, at room temperature Li / Ch batteries exhibited reversible Li / Li+and C17Ch redox reactions at a capacity of about 1200 mAh g-1, with a discharge voltage of about 3.5 V, indicating KJCO2 in the positive electrode effectively trapped Ch in the abundant nanoscale pores of KJCO2. At a lower temperature of -40 °C, the reversible capacity for C17Ch redox, with a discharge voltage of about 3.3 V, increased to about 2500 mAh g-1, indicating increased trapping of Ch in KJCCh at -40°C. At an even lower temperature of -80°C, the reversible capacity for C17Ch redox further increased to about4000 mAh g-1, and even more reactive species such as SCI2 / S2CI2 were retained on the positive electrode side, resulting in a high discharge voltage plateau at about 3.8 V with a specific capacity up to 1000 mAh g-1. These batteries showed longer cycle lives at lower temperatures under smaller cycling capacities due to reduced shuttling effects.EXAMPLE 5: Solid-Electrolyte Interface at the Li Negative Electrode

[0096] Lastly, characteristics of the SEI layer on a Li metal negative electrode was investigated by ex-situ XPS characterization after the negative electrode was removed from a Li / Ch battery with a KJCO2 positive electrode that had been cycled at -40°C for 10 cycles at 1200 mAh g-1. XPS results indicated that the dominant composition in the SEI on the Li negative electrode was LiCl which may have formed upon exposure of the Li negative electrode to the electrolyte due to the Li reaction with SOCI2 (FIG. 6D). LiF was also identified in the SEI (FIG. 6D), which may be attributed to reactions between Li with FST additive in the electrolyte. The fluoride component may have imparted greater stability to the SEI and cycling stability to the battery. In addition to LiCl and LiF, XPS also indicated the SEI contained F-S species, which may be attributed to FST decomposition, FIG. 6D), SiCh (which may be attributed to residue from the separator), - SO2-, Li2SO4, Li2SO3, Li2S, Li2Sx, (FIG. 6D), and AlCh, suggesting reactions between the Li metal and species in the electrolyte including reactive species generated at the positive electrode (e.g., CI2, SCI2, SO2CI2) that shuttled to the Li negative electrode.

[0097] Cross-sectional SEM imaging of the Li negative electrode was performed to further characterize the SEI on the Li metal. The SEI layer on the Li negative electrode after the negative electrode was cycled in a battery at room temperature was thicker and much more irregular than that formed through cycling at -40°C (FIG. 6E). The thicker and more irregular SEI formed at room temperature may be attributed to stronger shuttling effects and more severe side reactions / corrosions of Li due to reactive species escaping from the positive electrode. This finding is consistent with the reduced cycling performance of Li / Ch batteries and poorer retention of reactive species at higher temperatures (e.g., room temperature).- l-EXAMPLE 6: Probing the Effects of Different Carbon Positive Electrodes

[0098] Li / Ch batteries using different types of carbon positive electrodes were cycled to determine the electrochemical cycling effects of the different positive electrodes. Carbon positive electrodes included hollow carbon spheres (HCS) with and without CO2 activation, KJ without CO2 activation, amorphous carbon nanosphere (aCNS), and few wall carbon nanotubes (FWCNT).

[0099] FIG. 8 is a graph of the first discharge curves of room temperature Li / Ch battery with a positive electrode including HCS (hollow carbon sphere) with or with CO2 activation, using an electrolyte with 1.0 M AlCh and 0.95 M LiCl dissolved in SOCh with 0.05 M of LiFSI additive.

[0100] HCS was activated with CO2 by annealing HCS using a horizontal tube furnace in an environment of flowing CO2 at a flow rate of about 200 cc min'1. The annealing temperature was 900°C or 1000°C and the annealing time was 40 minutes. The temperature was increased from room temperature to 900°C or 1000°C at a rate of 10°C min'1. After annealing, the system was allowed to cool down naturally.

[0101] The results in FIG. 8 indicate that HCS positive electrodes, with CO2 activation at 900°C or 1000°C may be used in Li / Ch batteries to deliver a first discharge capacity greater than 17000 mAh g-1and 25000 mAh g-1, respectively, with a discharge voltage plateau of about 3.55 V. Annealing at the higher temperature of 1000°C resulted in a higher first discharge capacity.

[0102] FIGS. 9A-9B are directed to battery cycling performance of a Li / Ch battery at -40°C using a positive electrode with KJ without CO2 activation, as a comparison to the batteries described in Examples 1-5, which used activated KJCO2. FIG. 9A is a graph of the first discharge curve of the battery cycled at -40°C with a current of 50 mA g'1. FIG. 9B is a graph of cycling performance of the battery cycled at -40°C with a cycling capacity of 1200 mAh g-1and a current of 100 mA g-1.

[0103] In stark contrast, the -40 °C Li / Ch battery using KJ without CO2 activation only cycled less than 100 cycles at a capacity of 1200 mAh g-1, as compared to the battery with KJCO2 which cycled stable for over 130 cycles. The Li / Ch battery using KJ withoutCO2 activation also had a lower first discharge capacity of 3400 mAh g-1, as compared to the Li / Ch battery with KJCO2, which had a first discharge capacity of 5532 mAh g-1. The Li / Ch battery with KJ without CO2 activation also had a lower CE of less than 96%, as compared to the Li / Ch battery with KJCO2, which had a CE greater than 99%.

[0104] FIGS. 10A-10B are directed to battery cycling performance of a battery with a positive electrode containing aCNS. FIG. 10A is a graph of the first discharge curve of the Li / Ch battery cycled at -40°C using aCNS with a current of 50 mA g'1. FIG. 10B is a graph of cycling performance of the Li / Ch battery cycled at -40°C using aCNS with a cycling capacity of 1200 mAh g-1and a current of 100 mA g'1.

[0105] The -Li / Ch battery using an aCNS positive electrode cycled at -40°C only cycled less than 60 cycles at a capacity of 1200 mAh g-1, as compared to a battery using a KJCO2 positive electrode, which exhibited stable cycling over more thanl30 cycles. The battery using aCNS also had a lower first discharge capacity of 1750 mAh g-1, as compared to a battery using KJCO2, which had a first discharge capacity of 5532 mAh g-1. The battery using aCNS also had a lower CE of less than 98%, as compared to a battery using KJCO2, which had a CE greater than 99%.

[0106] FIGS. 11A-11B are directed to battery cycling performance of a battery with a few- walled carbon nanotube (FWCNT) positive electrode. FIG. 11A is a graph of the first discharge curve of a Li / Ch battery using a positive electrode with FWCNT activated at 1000°C in CO2. The discharge curve was measured at -40°C with 50 mA g'1current. The battery using the activated FWCNT positive electrode had a first discharge capacity of 1750 mAh g-1, which was lower than that of a battery with a KJCO2 positive electrode, as discussed above. FIG. 1 IB is a graph of cycling performance of the -40°C Li / Ch battery using the activated FWCNT positive electrode using a cycling capacity of 1200 mAh g-1with a current of 100 mA g'1. The battery cycled under these conditions for less than 50 cycles before failure and had a low CE less than 98%.EXAMPLE 7: Probing the Effects of Fluorine-Based Electrolyte Additive

[0107] FIGS. 12A-12B are directed to battery cycling performance at -40°C where the battery electrolyte includes or does not include an LiFSI additive at a concentration of 0.05 M. FIG. 12A is a graph of cycling performance of Li / Ch batterieswith KJCO2 positive electrodes, where the electrolyte either includes or does not include LiFSI present in a concentration of 0.05 M. Cycling was performed with a capacity of 1200 mAh g-1at -40°C and with a current of 100 mA g'1. Without the FSI additive, the battery failed after less than 50 cycles, whereas when the additive was present, the battery continued to cycle for more than 60 cycles. However, CE was lower in the first few cycles in the battery with the FSI additive. FIG. 12B is a graph of charge-discharge curves (at 20th cycle) of -40°C Li / Ch batteries with KJCO2 positive electrodes, with or without 0.05 M LiFSI additive, at 1200 mAh g-1cycling capacity with 100 mA g'1current.

[0108] While certain embodiments have been illustrated and described, it should be understood that changes and modifications can be made therein in accordance with ordinary skill in the art without departing from the technology in its broader aspects as defined in the following claims.

[0109] The embodiments, illustratively described herein may suitably be practiced in the absence of any element or elements, limitation or limitations, not specifically disclosed herein. Thus, for example, the terms “comprising,” “including,” “containing,” etc. shall be read expansively and without limitation. Additionally, the terms and expressions employed herein have been used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed technology. Additionally, the phrase “consisting essentially of’ will be understood to include those elements specifically recited and those additional elements that do not materially affect the basic and novel characteristics of the claimed technology. The phrase “consisting of’ excludes any element not specified.

[0110] The present disclosure is not to be limited in terms of the particular embodiments described in this application. Many modifications and variations can be made without departing from its spirit and scope, as will be apparent to those skilled in the art. Functionally equivalent methods and compositions within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms ofthe appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, reagents, compounds, compositions, or biological systems, which can of course vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.

[0111] In addition, where features or aspects of the disclosure are described in terms of Markush groups, those skilled in the art will recognize that the disclosure is also thereby described in terms of any individual member or subgroup of members of the Markush group.

[0112] As will be understood by one skilled in the art, for any and all purposes, particularly in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. As will also be understood by one skilled in the art all language such as “up to,” “at least,” “greater than,” “less than,” and the like, include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, as will be understood by one skilled in the art, a range includes each individual member.

[0113] All publications, patent applications, issued patents, and other documents referred to in this specification are herein incorporated by reference as if each individual publication, patent application, issued patent, or other document was specifically and individually indicated to be incorporated by reference in its entirety. Definitions that are contained in text incorporated by reference are excluded to the extent that they contradict definitions in this disclosure.

[0114] Other embodiments are set forth in the following claims.

Claims

WHAT IS CLAIMED IS:

1. An electrochemical device comprising: a negative electrode comprising lithium metal; a positive electrode comprising a carbonaceous material having a pore volume of about 6.1 cm3g-1to about 7 cm3g-1; and an electrolyte, wherein the electrolyte comprises aluminum chloride present in a concentration of about 0.5 M to about 1.2 M in thionyl chloride.

2. The electrochemical device of claim 1, wherein the carbonaceous material is treated by heating the carbonaceous material at about 900°C to about 1100°C in the presence of CO2, N2, water, or a combination thereof.

3. The electrochemical device of claim 1 or claim 2, wherein the carbonaceous material has a surface area of about 2000 m2g-1to about 3000 m2g-1.

4. The electrochemical device of any one of claims 1 to 3, wherein the electrolyte further comprises lithium chloride and lithium bis(trifluoromethanesulfonyl)imide.

5. The electrochemical device of any one of claims 1 to 4, wherein the electrolyte comprises aluminum chloride present in a concentration of about 0.9 M to about 1.1 M.

6. The electrochemical device of claim 4 or claim 5, wherein the electrolyte comprises lithium chloride present in a concentration of about 0.7 M to about 1.2 M.

7. The electrochemical device of any one of claims 4 to 6, wherein the electrolyte comprises lithium bis(trifluoromethanesulfonyl)imide present in a concentration of about 0.02 M to about 0.08 M.

8. The electrochemical device of any one of claims 1 to 7, wherein the electrolyte has a viscosity at -40°C that is about 3 times higher than the viscosity at 20°C.

9. The electrochemical device of any one of claims 1 to 8, wherein the positive electrode further comprises lithium chloride deposited on the carbonaceous material.

10. The electrochemical device of any one of claims 1 to 8, wherein the positive electrode further comprises LiCl, SOCh, Ch, SCh, S2CI2, or SO2CI2 within pores of the carbonaceous material.

11. The electrochemical device of any one of claims 1 to 10, wherein the positive electrode further comprises nickel foam and the carbonaceous material is deposited on the nickel foam.

12. A method of cycling an electrochemical device, the method comprising: operating the electrochemical device at a temperature of about -85°C to about -20°C; wherein the operating comprises delivering a specific capacity of about 1000 mAh g-1to about 5000 mAh g-1over 50 electrochemical cycles using the electrochemical device; and wherein an electrolyte in the electrochemical device comprises a metal halide and thionyl chloride.

13. The method of claim 12, wherein of the operating is performed at about -75°C to about -85°C and comprises delivering a specific capacity of about 1100 mAh g-1to about 1200 mAh g-1over at least 70 electrochemical cycles.

14. The method of claim 12, wherein the operating is performed at about -35°C to about -45°C and comprises delivering a specific capacity of about 2400 mAh g-1to about 2500 mAh g-1over at least 70 electrochemical cycles.

15. The method of claim 12, wherein of the operating is performed at about -35°C to about -45°C and comprises delivering a specific capacity of about 1100 mAh g-1to about 1200 mAh g-1over at least 100 electrochemical cycles.

16. The method of any one of claims 12 to 15, wherein the metal halide in the electrolyte comprises aluminum chloride present in a concentration of about 0.5 M to 1.2 M.

17. The method of any one of claims 12 to 16, wherein the metal halide in the electrolyte comprises lithium chloride present in a concentration of about 0.7 M to 1.2 M.

18. The method of any one of claims 12 to 17, wherein the electrolyte further comprises lithium bis(trifluoromethanesulfonyl)imide present in a concentration of about 0.02 M to 0.08 M.

19. A positive electrode for an electrochemical device comprising: a substrate comprising nickel foam, stainless steel, or a combination thereof; and a carbonaceous material deposited on the substrate, the carbonaceous material having a pore volume of about 6.1 cm3g-1to about 7 cm3g-1and a surface area of about 2000 m2g-1to about 3000 m2g-1, wherein the carbonaceous material is treated by heating the carbonaceous material in the presence of CO2 at about 900°C to about 1100°C.

20. The positive electrode of claim 19, further comprising lithium chloride deposited on the carbonaceous material.

21. The positive electrode of claim 19, further comprising Ch, SCI2, S2CI2, or SO2CI2 within pores of the carbonaceous material.

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