Disclosed are a crosslinked separator for a lithium secondary battery which comprises a crosslinked polyolefin porous substrate including a plurality of fibrils and pores formed by the fibrils entangled with one another, wherein polyolefin chains forming the fibrils are crosslinked directly with one another; and shows a change in tensile strength of 20% or less in the machine direction, as compared to a non-crosslinked separator including a polyolefin porous substrate before crosslinking, and a method for manufacturing the same. The crosslinked separator for a lithium secondary battery has excellent thermal safety, while not adversely affecting the other physical properties.

A separator for a secondary battery including a polyolefin and a separator body having a porous structure. The separator body has a difference in porosity along a thickness direction. It is possible to improve the problem of imbalance in ionic conductivity caused by differences in thickness and electrical conductivity between a positive electrode and a negative electrode.

Separator systems for electrochemical systems providing electronic, mechanical and chemical properties useful for applications including electrochemical storage and conversion. Separator systems include structural, physical and electrostatic attributes useful for managing and controlling dendrite formation and for improving the cycle life and rate capability of electrochemical cells including silicon anode based batteries, air cathode based batteries, redox flow batteries, solid electrolyte based systems, fuel cells, flow batteries and semisolid batteries. Separators include multilayer, porous geometries supporting excellent ion transport properties, providing a barrier to prevent dendrite initiated mechanical failure, shorting or thermal runaway, or providing improved electrode conductivity and improved electric field uniformity, as well as composite solid electrolytes with supporting mesh or fiber systems providing solid electrolyte hardness and safety with supporting mesh or fiber toughness and long life required for thin solid electrolytes without fabrication pinholes or operationally created cracks.

An object is to provide a battery-separator nonwoven fabric and a battery separator that are excellent in heat resistance, have a small pore diameter, and have a high tensile elongation and a high thrust strength, and a solution is to configure a battery-separator nonwoven fabric with a fiber A including a nanofiber having a fiber diameter of 100 to 1000 nm, a fiber B including a thermal adhesive ultrafine fiber having a fiber diameter of 100 to 2000 nm, and a fiber C including a thermal adhesive fiber having a single fiber fineness of 0.1 dtex or more, in which a tensile elongation of the nonwoven fabric is 10% or more.

Provided is a microporous film which has a surface A and a surface B opposite to the surface A. In one embodiment, the microporous film has a ratio (F.sub.B/F.sub.A) of a dynamic friction coefficient F.sub.B of the surface B to a dynamic friction coefficient F.sub.A of the surface A of 1.2 to 20. In another embodiment, the microporous film is a single layer having a thickness of 3-18 μm, a number N.sub.A of pores on the surface A is 10-100/μm.sup.2, a number N.sub.B of pores on the surface B is 20-200/μm.sup.2, and N.sub.A/N.sub.B is 0.2-0.96. In addition, a total area S.sub.A of pores on the surface A is 0.02-0.5 μm.sup.2/μm.sup.2, a total area S.sub.B of pores on the surface B is 0.01-0.3 μm.sup.2/μm.sup.2, and S.sub.A/S.sub.B is 1.1-10. Furthermore, in another embodiment, a number W.sub.B of protrusion-like bodies on the surface B is 0.2-1000/100 μm.sup.2.

A separator for an electricity storage device comprising a silane-modified polyolefin, wherein silane crosslinking reaction of the silane-modified polyolefin is initiated when it contacts with the electrolyte solution, as well as a method for producing the separator.

Improved high energy capacity designs for lithium ion batteries are described that take advantage of the properties of high specific capacity anode active compositions and high specific capacity cathode active compositions. In particular, specific electrode designs provide for achieving very high energy densities. Furthermore, the complex behavior of the active materials is used advantageously in a radical electrode balancing design that significantly reduced wasted electrode capacity in either electrode when cycling under realistic conditions of moderate to high discharge rates and/or over a reduced depth of discharge.

An embodiment is directed to a separator with a ceramic-comprising separator layer. The ceramic-comprising separator layer comprises porous metal oxide fibers with diameters in the range from around 3 nm to around 2 microns, aspect ratios in the range from around 20 to around 100,000, and a total open pore volume among the porous metal oxide fibers in the range from around 0.01 cm.sup.3/g to around 1 cm.sup.3/g.

Described herein is a multilayer microporous film or membrane that may exhibit improved properties, including improved dielectric break down and strength, compared to prior monolayer or tri-layer microporous membranes of the same thickness. The preferred multilayer microporous membrane comprises microlayers and one or more lamination barriers. Also disclosed is a battery separator or battery comprising one or more of the multilayer microporous films or membranes. The inventive battery and battery separator is preferably safer and more robust than batteries and battery separators using prior monolayer and tri-layer microporous membranes. Also, described herein is a method for making the multilayer microporous separators, membranes or films described herein.

Described herein is a multilayer microporous film or membrane that may exhibit improved properties, including improved dielectric break down and strength, compared to prior monolayer or tri-layer microporous membranes of the same thickness. The preferred multilayer microporous membrane comprises microlayers and one or more lamination barriers. Also disclosed is a battery separator or battery comprising one or more of the multilayer microporous films or membranes. The inventive battery and battery separator is preferably safer and more robust than batteries and battery separators using prior monolayer and tri-layer microporous membranes. Also, described herein is a method for making the multilayer microporous separators, membranes or films described herein.