Provided herein is a separator used for an electrochemical device such as a lithium-ion battery. The separator disclosed herein comprises a porous base material, a first protective porous layer coated on one side of the porous base material, and a second protective porous layer coated on the other side of the porous base material, wherein the first protective porous layer comprises an organic binder and a first inorganic filler, and wherein the second protective porous layer comprises an organic binder and a second inorganic filler different from the first inorganic filler. Also provided herein is a lithium-ion battery including the separator disclosed herein. The separator disclosed herein is excellent in terms of safety, ion permeability, and cycle characteristics.

A negative electrode active material includes a silicon-based alloy represented by Si-M.sub.1-M.sub.2-C—B, wherein M.sub.1 and M.sub.2 are different from each other and are each independently selected from magnesium, aluminum, titanium, vanadium, chromium, iron, cobalt, nickel, copper, zinc, gallium, germanium, manganese, yttrium, zirconium, niobium, molybdenum, silver, tin, tantalum, and tungsten. In the silicon-based alloy, Si is in a range of about 50 at % to about 90 at %, M.sub.1 is in a range of about 10 at % to about 50 atom %, and M.sub.2 is in a range of 0 at % to about 10 at %, based on a total number of Si, M.sub.1, and M.sub.2 atoms. C is in a range of about 0.01 to about 30 parts by weight, and B is in a range of 0 to about 5 parts by weight, based on a total of 100 parts by weight of Si, M.sub.1, and M.sub.2.

An enhanced solid state battery cell is disclosed. The battery cell can include a first electrode, a second electrode, and a solid state electrolyte layer interposed between the first electrode and the second electrode. The battery cell can further include a resistive layer interposed between the first electrode and the second electrode. The resistive layer can be electrically conductive in order to regulate an internal current flow within the battery cell. The internal current flow can result from an internal short circuit formed between the first electrode and the second electrode. The internal short circuit can be formed from the solid state electrolyte layer being penetrated by metal dendrites formed at the first electrode and/or the second electrode.

In the present invention, in laminated separator rolls 12U and 12L, laminated long separator sheets 12a and 12b are wound such that a surface B (which is of an aramid layer (heat-resistant layer) and is opposite to a surface contacting with the porous film) faces an inner side (core u, l side). From this, it is possible to provide the laminated separator roll which can inhibit change in color of the porous layer included in the porous long separator sheet.

In the present invention, a porous separator roll (12U, 12L) is wrapped with a wrapping material (21) whose average transmittance with respect to light having a wavelength of 360 nm to 390 nm is 25% or lower. From this, it is possible to provide a package of a porous separator roll which package can inhibit change in color of a separator, and can thus provide a high-quality separator with good appearance.

A fiber-containing polymer film contains a host polymer and fibrous substances. The fiber-containing polymer film has an orientation area where the fibrous substances are oriented in a direction substantially parallel to a main surface of the fiber-containing polymer film and in substantially the same direction.

A nonaqueous electrolyte secondary battery includes a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode. The separator includes a substrate layer and a surface layer formed on at least one principal plane of the substrate layer, the surface layer contains polyvinylidene fluoride and an inorganic material particle, and an amount of deformation against pressure of the surface layer is larger than that of the substrate layer.

The battery is sealed by a sealing member including a safety valve for exhausting the gas generated in the battery to the outside of the battery when the pressure in the battery is increased. A part of the sealing member is formed of a member having a melting point lower than that of high-temperature gas generated in the abnormal time and having a ratio of an area of an opening of the battery case to an area of a gas exhaust hole is 3.0×10.sup.−5 or more and 9.1×10.sup.−3 or less.

A lithium metal battery including: a lithium negative electrode including lithium metal; a positive electrode; and an electrolyte interposed between the lithium negative electrode and the positive electrode, wherein the electrolyte contains non-fluorine substituted ether, which is capable of solvating lithium ions, a fluorine substituted ether represented by the following Formula 1, and a lithium salt, wherein an amount of the fluorine substituted ether represented by Formula 1 is greater than an amount of the non-fluorine substituted ether,
R—{O(CH.sub.2).sub.a}.sub.b—CH.sub.2—O—C.sub.nF.sub.2nH  Formula 1 wherein R is —C.sub.mF.sub.2mH or —C.sub.mF.sub.2m+1, n is an integer of 2 or greater, m is an integer of 1 or greater, a is an integer of 1 or 2, and b is 0 or 1.

A method for producing a polyolefin-based porous film includes an (A) step: a raw fabric forming step for forming a non-porous raw fabric from a polyolefin-based resin composition, a (B) step: an MD cold stretching step for cold stretching the non-porous raw fabric obtained in the (A) step at a temperature of −20° C. to (Tm−30)° C. (Tm is a melting point (° C.) of the non-porous raw fabric) in an extruding direction (MD) of the raw fabric to make the raw fabric porous; a (D) step: a TD cold stretching step for cold stretching a film processed in the (B) step in a direction (TD) perpendicular to the MD, and an (H) step: a thermal fixing step, in the above order.