The present invention relates to a calcium-based secondary cell containing: an electrolyte arranged between the negative electrode and the positive electrode and comprising a calcium salt of a fluorine-containing anion of formula (XF.sub.n).sup.m− wherein n is a positive integer of at most 6 and m is a positive integer of at least 1 and m<n, a positive-electrode active material at the positive electrode which is a one-dimensional structure accommodating Ca.sup.2+ ions and has the formula (1):
Ca.sub.n+2Me1.sub.(n+1)−y−zMe2.sub.yMe3.sub.zO.sub.3n+3  (1)
wherein: Me1, Me2, Me3 are different transition metals; 1≤n and n is not necessarily an integer; 0≤y and y is not necessarily an integer; 0≤z and z is not necessarily an integer.

A method for manufacturing a negative electrode active material includes: an alloying step of causing an Na source and an Si source to react to produce an Na—Si alloy containing Na and Si; and a silicon clathrate production step of heating the Na—Si alloy and reducing an amount of Na in the Na—Si alloy to produce a type-II silicon clathrate. Porous Si with a BET specific surface area of 20 m.sup.2/g or more is used as the Si source.

Provided herein are energy storage devices. In some cases, the energy storage devices are capable of being transported on a vehicle and storing a large amount of energy. An energy storage device is provided comprising at least one liquid metal electrode, an energy storage capacity of at least about 1 MWh and a response time less than or equal to about 100 milliseconds (ms).

An anode includes a mixed ionic-electronic conductor (MIEC) with an open pore structure. The open pore structure includes open pores to facilitate motion of an alkali metal into and/or out of the MIEC. The open pore structure thus provides open space to relieve the stresses generated by the alkali metal when charging/discharging a battery. The MIEC is formed from a material that is thermodynamically and electrochemically stable against the alkali metal to prevent the formation of solid-electrolyte interphase (SEI) debris and the formation of dead alkali metal. The MIEC may also be passive (the MIEC does not store or release alkali metal). In one example, the open pore structure may be an array of substantially aligned tubules with a width less than about 300 nm, a wall thickness between about 1 nm to about 30 nm, and a height of at least 10 um arranged as a honeycomb.

A battery, having polyvalent aluminum metal as the electrochemically active anode material and also including a solid ionically conducting polymer material.

A rechargeable battery using a solution of an aluminum salt as an electrolyte is disclosed, as well as methods of making the battery and methods of using the battery.

A sodium-ion conducting (e.g., sodium-sulfur) battery, which can be rechargeable, comprising a microporous host-sulfur composite cathode as described herein or a liquid electrolyte comprising a liquid electrolyte solvent and a liquid electrolyte salt or electrolyte additive as described herein or a combination thereof. The batteries can be used in devices such as, for example, battery packs.

Provided is a novel production method for producing silicon clathrate II. In the production method for producing silicon clathrate II, in a reaction system in which a Na—Si alloy containing Na and Si and an Na getter agent coexist so as not to be in contact with each other, the Na—Si alloy is heated and Na evaporated from the Na—Si alloy is thus caused to react with the Na getter agent to reduce an amount of Na in the Na—Si alloy.

There is provided a composite comprising a) a short chain sulfur; and b) a carbon-supported conductive polymer such as polyacrylonitrile, wherein sulfur atoms of said short chain sulfur are covalently linked to the conductive polymer of said carbon-supported conductive polymer via a C—S bond. A method of preparing said composite comprising polymerizing a plurality of monomers in the presence of a carbon scaffold, mixing elemental sulfur and heating the mixture to obtain said composite is also disclosed. An electrochemical cell comprising said composite as cathode, a sodium anode and a liquid electrolyte such as sodium trifluoromethanesulfonate dissolved in a mixture of solvents is disclosed.

Alkali metal secondary batteries that include anodes constructed from alkali metal foil applied to only one side of a porous current collector metal foil. Openings in the porous current collectors permit alkali metal accessibility on both sides of the anode structure. Such anode constructions enable the utilization of lower-cost and more commonly available alkali metal foil thickness, while still achieving high cell cycle life at a significantly reduced cost. Aspects of the present disclosure also include batteries with porous current collectors having increased volumetric and gravimetric energy densities, and methods of manufacturing anodes with porous current collectors.