MEMBRANES, CALENDERED MICROPOROUS MEMBRANES, BATTERY SEPARATORS, AND RELATED METHODS

摘要

Novel or improved microporous single or multilayer battery separator membranes, separators, batteries including such membranes or separators, methods of making such membranes, separators, and/or batteries, and/or methods of using such membranes, separators and/or batteries are provided. In accordance with at least certain embodiments, a multilayer dry process polyethylene/polypropylene/polyethylene microporous separator which is manufactured using the inventive process which includes machine direction stretching followed by transverse direction stretching and a subsequent calendering step as a means to reduce the thickness of the multilayer microporous membrane, to reduce the percent porosity of the multilayer microporous membrane in a controlled manner and/or to improve transverse direction tensile strength. In a very particular embodiment, the inventive process produces a thin multilayer microporous membrane that is easily coated with polymeric-ceramic coatings, has excellent mechanical strength properties due to its polypropylene layer or layers and a thermal shutdown function due to its polyethylene layer or layers. The ratio of the thickness of the polypropylene and polyethylene layers in the inventive multilayer microporous membrane can be tailored to balance mechanical strength and thermal shutdown properties.

主权项

1. A battery separator for a lithium battery comprising at least one microporous membrane having at least one outer surface or surface layer having a unique pore structure with a pore being the opening or space between adjacent lamellae and which may be bounded on one or both sides by a fibril or bridging structure between the adjacent lamellae and wherein at least a portion of the membrane contains respective groups of pores between adjacent lamellae with the lamellae oriented substantially along a transverse direction and the fibrils or bridging structures between the adjacent lamellae oriented substantially along a machine direction and the outer surface of at least some of the lamellae being substantially flattened or planar, and wherein the pore structure having at least one of: substantially trapezoidal or rectangular pores, pores with rounded corners, condensed or heavy lamellae across the width or transverse direction, fairly random or less ordered pores, groups of pores with areas of missing or broken fibrils, densified lamellar skeletal structure, groups of pores with a TD/MD length ratio of at least 4, groups of pores with a TD/MD length ratio of at least 6, groups of pores with a TD/MD length ratio of at least 8, groups of pores with a TD/MD length ratio of at least 9, groups of pores with at least 10 fibrils, groups of pores with at least 14 fibrils, groups of pores with at least 18 fibrils, groups of pores with at least 20 fibrils, pressed or compressed stacked lamellae, a uniform surface, a slightly non-uniform surface, a low COF, or combinations thereof.