Disclosed is a calcium salt, Ca(HMDS).sub.2, where HMDS is the hexamethyldisilazide anion (also known as bis(trimethylsilyl)amide), enables high current densities and high coulombic efficiency for calcium metal deposition and dissolution. These properties facilitate the use of this salt in batteries based on calcium metal. In addition, the salt is significant for batteries based on metal anodes, which have higher specific energies than batteries based on intercalation anodes, such as LiC.sub.6. In particular, a calcium based rechargeable battery includes Ca(HMDS).sub.2 salt and at least one solvent, the solvent suitable for calcium battery cycling. The at least one solvent can be diethyl ether, diisopropylether, methyl t-butyl ether (MTBE), 1,3-dioxane, 1,4-dioxane, tetrahydrofuran (THE), tetrahydropyran, glyme, diglyme, triglyme or tetraglyme, or any mixture thereof.

The disclosure includes a composition of matter including a film formed on substantially all nSi-cPAN particles included in an electrode, the film including fluorine, oxygen, sulfur, carbon and lithium.

Disclosed is a calcium salt, Ca(HMDS).sub.2, where HMDS is the hexamethyldisilazide anion (also known as bis(trimethylsilyl)amide), enables high current densities and high coulombic efficiency for calcium metal deposition and dissolution. These properties facilitate the use of this salt in batteries based on calcium metal. In addition, the salt is significant for batteries based on metal anodes, which have higher specific energies than batteries based on intercalation anodes, such as LiC.sub.6. In particular, a calcium based rechargeable battery includes Ca(HMDS).sub.2 salt and at least one solvent, the solvent suitable for calcium battery cycling. The at least one solvent can be diethyl ether, diisopropylether, methyl t-butyl ether (MTBE), 1,3-dioxane, 1,4-dioxane, tetrahydrofuran (THF), tetrahydropyran, glyme, diglyme, triglyme or tetraglyme, or any mixture thereof.

A secondary battery having good performance especially in a high-temperature environment can be obtained by using an electrolyte solution for secondary batteries, which is characterized by containing an ionic liquid represented by formula (1) and a lithium salt.

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(In the formula, each of R.sup.1 and R.sup.2 independently represents an alkyl group having 1-5 carbon atoms; and n represents 1 or 2.)

A metal-ion battery is provided. The metal-ion secondary battery includes a positive electrode, a first negative electrode, a first separator, a second negative electrode, a second separator, and a control element, wherein the first separator is disposed between the positive electrode and the first negative electrode, and the second separator is disposed between the first negative electrode and the second negative electrode. Furthermore, the control element is coupled to the first negative electrode and the second negative electrode, wherein the control element determines whether to electrically connect the first negative electrode to the second negative electrode.

A metal-ion battery are provided. The disclosure provides a metal-ion battery. The metal-ion battery includes a positive electrode; a negative electrode, wherein the negative electrode is a metal or an alloy thereof, the metal is Cu, Fe, Zn, Co, In, Ni, Sn, Cr, La, Y, Ti, Mn, or Mo; a separator, wherein the positive electrode is separated from the negative electrode by the separator; and an electrolyte, disposed between the positive electrode and the negative electrode. The electrolyte includes ionic liquid, aluminum halide.

An electrochemical cell includes solid-state, printable anode layer, cathode layer and non-aqueous gel electrolyte layer coupled to the anode layer and cathode layer. The electrolyte layer provides physical separation between the anode layer and the cathode layer, and comprises a composition configured to provide ionic communication between the anode layer and cathode layer by facilitating transmission of multivalent ions between the anode layer and the cathode layer.

A Li-air battery is provided. The battery contains: an anode compartment containing lithium or a lithium alloy as active metal; a cathode compartment supplied with an O.sub.2 source; and a lithium ion conductive membrane separating the anode compartment from the cathode compartment. The cathode compartment contains an air electrode with a skin alloy platinum or palladium catalyst.

A polymer electrolyte includes a polyethylene oxide matrix, a plasticizer additive, a solute, and a filler. The plasticizer additive includes an ionic liquid and the filler includes zinc oxide. An energy storage device includes an anode, a cathode and the polymer electrolyte. An energy storage device includes a zinc anode, a cathode and a polymer electrolyte, in which the polymer electrolyte includes a polyethylene oxide matrix and a plasticizer additive that includes an ionic liquid.

Disclosed herein are lignin-derived ionic liquids and methods for preparing them. The methods include forming a reaction mixture comprising a lignin-derived starting material, a carbonyl compound, and an amine; maintaining the reaction mixture under conditions sufficient to form a lignin-derived aminophenol; and converting the lignin derived aminophenol to the lignin-derived ionic liquid. Monomeric phenols, oligomeric phenols, and polymeric phenols can be used as lignin-derived starting materials.