A lithium-ion secondary battery 100 includes a positive electrode current collector 221 and a porous positive electrode active material layer 223 retained by the positive electrode current collector 221. The positive electrode active material layer 223 contains, for example, positive electrode active material particles 610, an electrically conductive material 620, and a binder 630. In this lithium-ion secondary battery 100, the positive electrode active material particles 610 have a shell portion 612 constituted by a lithium transition metal oxide, a hollow portion 614 formed inside the shell portion 612, and a through hole 616 penetrating the shell portion 612. In the lithium-ion secondary battery 100, in the positive electrode active material layer 223 on average, the hollow portion 614 accounts for 23% or higher of an apparent sectional area of the positive electrode active material particles 610. In addition, a thickness of the shell portion 612 in the positive electrode active material layer 223 on average is 2.2 μm or less.

Disclosed is a cathode active material comprising a lithium manganese composite oxide with a spinel structure represented by the following Formula 1, wherein the lithium manganese composite oxide is surface-coated with a conductive polymer in an area of 30 to 100%, based on the surface area of the lithium manganese composite oxide:
Li.sub.xM.sub.yMn.sub.2-yO.sub.4-zA.sub.z  (1) wherein 0.9≦x≦1.2, 0<y<2, and 0≦z<0.2; M is at least one element selected from the group consisting of Al, Mg, Ni, Co, Fe, Cr, V, Ti, Cu, B, Ca, Zn, Zr, Nb, Mo, Sr, Sb, W, Ti and Bi; and A is at least one monovalent or bivalent anion. Disclosed is also a secondary battery comprising the cathode active material.

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.

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 lithium secondary battery includes a cathode including a cathode active material that includes lithium metal oxide particles, an anode facing the cathode and including an anode active material, and an electrolyte solution including a lithium salt and an organic solvent. The lithium metal oxide particles contain at least 80 mol % of nickel and less than 10 mol % of manganese among all elements excluding lithium and oxygen. The organic solvent includes an acetate-based compound in an amount from 1 vol % to 10 vol % based on a total volume of the organic solvent.

The invention is directed toward a primary AA alkaline battery. The primary AA alkaline battery includes an anode; a cathode; an electrolyte; and a separator between the anode and the cathode. The anode includes an electrochemically active anode material. The cathode includes an electrochemically active cathode material. The electrolyte includes a hydroxide. The primary AA alkaline battery has an integrated in-cell ionic resistance (R.sub.i) at 22° C. of less than about 39 mΩ.

The invention is directed toward a primary AA alkaline battery. The primary AA alkaline battery includes an anode; a cathode; an electrolyte; and a separator between the anode and the cathode. The anode includes an electrochemically active anode material. The cathode includes an electrochemically active cathode material. The electrolyte includes a hydroxide. The primary AA alkaline battery has an integrated in-cell ionic resistance (R.sub.i) at 22° C. of less than about 39 mΩ.

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.

Described herein is an aqueous aluminum ion battery featuring an aluminum or aluminum alloy/composite anode, an aqueous electrolyte, and a manganese oxide, aluminosilicate or polymer-based cathode. The battery operates via an electrochemical reaction that entails an actual transport of aluminum ions between the anode and cathode. The compositions and structures described herein allow the aqueous aluminum ion battery described herein to achieve: (1) improved charge storage capacity; (2) improved gravimetric and/or volumetric energy density; (3) increased rate capability and power density (ability to charge and discharge in shorter times); (4) increased cycle life; (5) increased mechanical strength of the electrode; (6) improved electrochemical stability of the electrodes; (7) increased electrical conductivity of the electrodes, and (8) improved ion diffusion kinetics in the electrodes as well as the electrolyte.

A battery comprising an anode comprising anode material in contact with a metal anode current collector. The battery further comprises a cathode comprising cathode material in contact with a cathode current collector comprising a transparent conducting oxide (TCO). The battery further comprises an electrolyte with a pH in a range of 3 to 7.