Patent Application
20100028778
1. Field of the Invention
The present invention relates to a method for the cutting of abrasive sheet stock, that is to say material in which abrasive particles are located inside and/or on the surface of a carrier.
2. Discussion of the Background
For use in lithium-ion batteries, inter alia, separators are employed which consist, for example, of a carrier substance coated with ceramic constituents or containing ceramic constituents. The ceramic constituents of these ceramic separators, as they are known, may consist of aluminium oxide (Al2O3) and silicon oxide (SiO2) and also further metal oxides, such as, for example, BaTiO3, ZrO2 or TiO2. The carrier substances may in this case consist, for example, of polymers, such as polyolefins, polyesters or polyimides. The ceramic constituents may both be introduced into the polymer, in which case the polymer serves as matrix and the oxide as filler, and be applied to a porous polymer carrier in the form of an impregnation, print or infiltration.
Ceramic or semi-ceramic (hybrid) separators or ceramic membranes which can be used as separators are sufficiently known, for example, from WO 99/15262. The production of separators or membranes which are suitable as separators may also be gathered from this publication. Preferably, however, electrically conductive carriers, such as, for example, metal fabrics, are not employed as porous carriers for the separators mentioned, since, when such carriers are used, internal short-circuits may occur if the ceramic coating of the carrier is incomplete. The said separators therefore preferably have carriers consisting of materials which are not electrically conductive.
Hybrid separators have recently been developed which have ceramics and polymers. In DE 102 08 277, separators were produced, based on polymeric substrate materials, such as, for example, polymer bonded webs, which have a porous electrically insulating ceramic coating.
Such ceramic separators are conventionally cut into the desired shape by means of customary commercially available cutting implements, such as circular knives, shears, lever shears, etc., with blades consisting of conventional or else hardened knife steel. The disadvantage in this case is that, sometimes, an enormous loss of material due to abrasion is observed when cutting is being carried out. The abrasion, in turn, often occurs in the form of harmful and at least disruptive dust.
Ceramic separators which, for example, take the form of roll stock are cut, for use in lithium-ion batteries, to the dimensions necessary for this purpose. Automatic and semi-automatic cutting tables are state of the art for this, while the material to be cut must be stable and is gripped by means of clamping devices, transported into the cutting device, cut under pressure and subsequently transported further on.
However, separators may be brittle or at least very thin. This procedure is therefore impossible, without damaging the material. Moreover, cutting transversely to the transport direction does not permit the continuous transport of the material which, in the case of separators, is mostly in the form of sheet stock. Cutting transversely to the transport direction is designated at this juncture and hereafter by cutting to length. Hereafter, cutting is understood to mean the cutting of sheet stock in the transport direction, this being equivalent to the direction in which this sheet stock is rolled up.
The result of the cutting to length of layered and therefore multi-ply sheet stock is that the upper plies are displaced laterally and/or pinched by the knife which on a microscopic scale is wedge-shaped.
An object of the present invention, therefore, is to provide a method for cutting to length of sheet stock, which permits a continuous transport of the sheet stock, in particular can be integrated into a continuous roll-to-roll process, by means of which sheet stock, in particular battery separator stock, is nowadays usually produced and handled.
Thus, the present invention relates to a method for the cutting of abrasive sheet stock, that is to say material in which abrasive particles are located inside and/or on the surface of a carrier. The present invention relates particularly to a method for the cutting of ceramic separators or separators containing ceramic or oxidic constituents, the said separators being used, for example, in lithium-ion batteries.
The present invention provides a method for the cutting to length of sheet stock which has a carrier and abrasive particles, the abrasive particles being located inside and/or on at least part of the surface of the carrier, the method comprising
The method according to the present invention has the advantage that it can be integrated into the continuous production process for sheet stock of any type, in particular separators. The advantage of the method according to the present invention is also that a separate step, necessary for cutting to length, to fix the sheet stock becomes unnecessary, since the sheet stock is fixed automatically by being wound up.
A further subject of the present invention is the made-up stock (cut sheet stock) which is obtained by the method according to the present invention, and also the use of the stock according to the present invention as a separator in batteries.
The present invention is explained in more detail hereafter by way of example.
In step (c) of the method according to the present invention, preferably a core or a tube can be used, the diameter of which amounts to 100 to 105 times the thickness of the sheet stock.
It may be advantageous, furthermore, in step (c) of the method according to the present invention, to use sheet stock having a thickness of 5 μm to 100 μm.
2 to 1000 plies of sheet stock can be wound onto the core or the tube in step (c), the number of plies being obtained from the rounded-off quotient of the difference between the largest diameter of the body, obtained according to step (c), perpendicularly to the body axis and the diameter of the core or of the tube and double the thickness of the sheet stock.
There is the possibility, in step (d) of the method according to the present invention, of using at least one fixed or rotating knife.
Preferably, in step (d), the sheet stock can be cut to length in a cut along the axis from outside in the direction of the axis of rotation of the body obtained according to step (c).
German patent application 10 2008 040894.8 filed Jul. 31, 2008, is incorporated herein by reference.
Numerous modifications and variations on the present invention are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102008040894.8 | Jul 2008 | DE | national |
