Apparatus and method for coating a functional layer

Abstract

An apparatus and method for coating a functional layer on a current collector with an active material layer thereon, the apparatus including a first roll and a second roll, the first roll and second roll being for advancing the current collector; a gravure roll, the gravure roll being configured to coat the functional layer on the active material layer; a thickness measurer, the thickness measurer being configured to measure at least one of a thickness of the active material layer and a sum thickness of the active material layer and the functional layer; and a controller, the controller being in communication with the thickness measurer and being configured to control a rotation speed of the gravure roll.

1 . An apparatus for coating a functional layer on a current collector with an active material layer thereon, the apparatus comprising:
 a first roll and a second roll, the first roll and second roll being for advancing the current collector;   a gravure roll, the gravure roll being configured to coat the functional layer on the active material layer;   a thickness measurer, the thickness measurer being configured to measure at least one of a thickness of the active material layer and a sum thickness of the active material layer and the functional layer; and   a controller, the controller being in communication with the thickness measurer and being configured to control a rotation speed of the gravure roll.   
     
     
         2 . The apparatus as claimed in  claim 1 , wherein the controller is configured to control the rotation speed of the gravure roll based on a difference between a thickness of the active material layer and a predetermined desired thickness. 
     
     
         3 . The apparatus as claimed in  claim 1 , wherein the controller is configured to control the rotation speed of the gravure roll based on a difference between the sum thickness and a predetermined desired thickness. 
     
     
         4 . The apparatus as claimed in  claim 1 , further comprising a doctor blade unit configured to scrape excess functional layer material off the gravure roll, wherein the controller is further configured to control a position of the doctor blade unit. 
     
     
         5 . A method of coating a functional layer on a current collector with an active material layer thereon, the method comprising:
 advancing the current collector with the active material layer thereon along a first roll and a second roll;   coating a functional layer on the active material layer with a gravure roll; and   controlling a rotational speed of the gravure roll such that a sum thickness of the functional layer and the active material layer is uniform along a length of the functional layer.   
     
     
         6 . The method as claimed in  claim 5 , wherein coating the functional layer includes:
 measuring a thickness of the active material layer with a measurer,   comparing the thickness of the active material layer with a predetermined desired thickness,   forming a functional layer on the active material layer such that the sum thickness of the functional layer and the active material layer equals the predetermined desired thickness.   
     
     
         7 . The method as claimed in  claim 5 , wherein controlling the rotational speed includes:
 measuring a sum thickness of the active material layer and the functional layer with the measurer,   comparing the sum thickness with a predetermined desired thickness,   controlling a rotational speed of the gravure roll based on a difference between the sum thickness and the predetermined desired thickness.   
     
     
         8 . The method as claimed in  claim 7 , wherein:
 measuring a sum thickness of the active material layer and the functional layer takes place downstream of the gravure roll, and   controlling the rotational speed of the gravure roll based on the difference between the sum thickness and the predetermined desired thickness includes controlling the sum thickness of an active material layer and functional layer and takes place upstream of the measurer based on measurement of the sum thickness by the measurer downstream of the gravure roll.   
     
     
         9 . An apparatus for coating a functional layer on a current collector with an active material layer thereon, the apparatus comprising:
 a gravure roll, the gravure roll being configured to coat the functional layer on the active material layer;   a doctor blade unit, the doctor blade unit including:
 a doctor blade, the doctor blade unit being configured to scrape excess functional layer material off the gravure roll with the doctor blade, and 
 at least one strain gauge, the at least one strain gauge being configured to measure a strain of the doctor blade; and 
   a controller, the controller being in communication with the at least one strain gauge and being configured to control a position of the doctor blade unit.   
     
     
         10 . The apparatus as claimed in  claim 9 , wherein the controller is configured to control the position of the doctor blade unit based on the strain of the doctor blade. 
     
     
         11 . The apparatus as claimed in  claim 10 , wherein the doctor blade unit includes:
 a support between the doctor blade and the at least one strain gauge,   a holder, the holder holding the support and the doctor blade, and   at least one servo motor, the at least one servo motor being controlled by the controller and being configured to move the holder relative to the gravure roll and change a pressure between the doctor blade and the gravure roll.   
     
     
         12 . The apparatus as claimed in  claim 10 , wherein the controller is further configured to control a rotational speed of the gravure roll. 
     
     
         13 . A method of coating a functional layer on a current collector with an active material layer thereon, the method comprising:
 detecting a measured strain on a doctor blade;   comparing the measured strain with an optimum value for strain on the doctor blade;   maintaining the doctor blade in an optimum blading state based on the detecting the measured strain and the comparing the measured strain with the optimum value for strain, thereby removing excess functional layer material from the gravure roll;   advancing the current collector having the active material layer thereon; and   coating the functional layer on the active material layer with the gravure roll such that a sum thickness of the functional layer and the active material layer is uniform across a length of the functional layer.   
     
     
         14 . The method as claimed in  claim 13 , wherein maintaining the doctor blade in the optimum blading state includes changing a pressure between the doctor blade and the gravure roll by moving the doctor blade relative to the gravure roll using at least one servo motor based on a difference between the measured strain and the optimum value for the strain. 
     
     
         15 . The method as claimed in  claim 13 , wherein maintaining the doctor blade in the optimum blading state includes detecting the measured strain with at least one strain gauge. 
     
     
         16 . The method as claimed in  claim 15 , wherein the at least one strain gauge is disposed on a support, the support being between the strain gauge and the doctor blade. 
     
     
         17 . The method as claimed in  claim 16 , wherein:
 the support and the doctor blade are held by a holder, and   the servo motor moves the holder relative to the gravure roll in order to change the pressure between the doctor blade and the gravure roll.   
     
     
         18 . The method as claimed in  claim 13 , wherein maintaining the doctor blade in the optimum blading state includes:
 setting the doctor blade in the optimum blading state against the gravure roll;   measuring the optimum value for strain with a strain gauge while the doctor blade is in the optimum blading state;   inputting the optimum value for strain to a controller;   continuously measuring a measured strain on the doctor blade with the strain gauge,   comparing the measured strain to the optimum value for strain, and   optimizing the pressure between the doctor blade and the gravure roll by moving the doctor blade relative to the gravure roll when the measured strain does not equal the optimum value for strain.   
     
     
         19 . The method as claimed in  claim 18 , wherein maintaining the doctor blade in the optimum blading state further includes sounding an alarm when a distance that the doctor blade has moved relative to the gravure roll is greater than a predetermined upper limit distance.