Multilayer material based on active lithium, method of preparation and applications in electrochemical generators

Abstract

A method for preparing a multilayer material based on active lithium, by depositing a film of active lithium on a protective layer at a sufficient speed so that substantially no oxidation of the lithium occurs, and/or during a sufficient time for the adhesion of the lithium to develop after contact with the protective layer. The multilayer material, when incorporated in an electrochemical battery as an anode, has excellent impedance stability and no formation of dendrites during the cycling. Batteries where the anode is the multilayer material are particularly efficient in terms of their coulomb efficiency.

1 . A method for preparing a multilayer material which comprises at least one layer of active lithium, said method comprising a step of depositing a film of active lithium on a protective layer at a sufficient speed so that substantially no oxidation of the lithium occurs, and/or during a sufficient time for the adhesion of the lithium to develop after contact with the protective layer. 
     
     
         2 . The method as claimed in  claim 1 , wherein the layer of active lithium consists essentially of lithium which has a degree of purity higher than 99%, or of a lithium alloy comprising less than 3000 ppm of impurities. 
     
     
         3 . The method as claimed in  claim 1 , wherein the layer of active lithium carries on one or each of its surfaces, a passivation layer which is such that the ratio “thickness of the passivation layer”/“thickness of the layer of active lithium” is between 2.10 −5  and 1.10 −3 . 
     
     
         4 . The method as claimed in  claim 1 , wherein the passivation layer comprises at least one lithium compound from the group consisting of Li 2 O, Li 2 CO 3 , LiOH, and Li 2 S 2 O 4 ; wherein the Li 2 O, Li 2 CO 3  and LiOH are formed in a dry atmosphere. 
     
     
         5 . The method as claimed in  claim 1 , wherein a protective layer is deposited on each of the surfaces of the film of active lithium, the two protective layers consisting essentially of an ion-conducting material. 
     
     
         6 . The method as claimed in  claim 1 , wherein the film of active lithium is deposited on a protective layer consisting essentially of an ion-conducting material. 
     
     
         7 . The method as claimed in  claim 1 , wherein the film of active lithium is deposited on a protective layer consisting essentially of an ion-conducting material and a protective layer consisting essentially of an electron-conducting material is deposited on the free surface of the film of active lithium. 
     
     
         8 . The method as claimed in  claim 1 , wherein the method is implemented in a dry air atmosphere, in an anhydrous chamber with a dew point between −45 and 55° C. and a relative humidity between 0.7 and 2.2%. 
     
     
         9 . The method as claimed in  claim 1 , wherein the protective layer is deposited in 1 to 15 seconds. 
     
     
         10 . The method as claimed in  claim 1 , wherein an ion-conducting protective layer comprises at least two sublayers, consisting essentially of, independently of one another, a material which has an ion conduction higher than 10 −4 S·cm 2 , and which is selected from ceramics, glasses, polymers, and polymers containing a ceramic filler. 
     
     
         11 . The method as claimed in  claim 1 , wherein the material constituting the protective layer consists essentially of a ceramic of the nonstoichiometric lithium phosphorus oxynitride type (LIPON). 
     
     
         12 . The method as claimed in  claim 1 , wherein the protective layer consists essentially of a ceramic or of a glass with a thickness equal to or less than 1 μm, of a solution of an ionic compound in a polymer, of a polymer carrying ionic groups, of a polymer containing a ceramic, of a polymer with a thickness between 1 and 100 μm, or of an electron conducting material. 
     
     
         13 . A multilayer material obtained as claimed in  claim 1 , comprising at least one layer of active lithium and one protective layer adhering to one another, wherein the lithium layer is a layer of active lithium which carries, on at least one of its surfaces, a continuous or discontinuous passivation layer having an average thickness of less than 50 Å, and wherein said at least one protective layer consists essentially of an ion-conducting material. 
     
     
         14 . The multilayer material as claimed in  claim 13 , wherein the two surfaces of the layer of active lithium carry an ion-conducting protective layer. 
     
     
         15 . The multilayer material as claimed in  claim 13 , wherein one of the surfaces of the layer of active lithium adheres to a protective layer consisting essentially of an ion-conducting material, and the other surface of the layer of active lithium adheres to a protective layer consisting essentially of an electron-conducting material. 
     
     
         16 . An electrochemical generator comprising at least one cathode, one electrolyte and at least one anode, wherein the anode comprises a multilayer material as claimed in  claim 13 . 
     
     
         17 . The generator as claimed in  claim 16 , wherein it comprises at least one assembly comprising the following elements, in the order indicated:
 a collector;   a cathode material;   a polymer electrolyte, or a separator impregnated with a gel electrolyte or a separator impregnated with a liquid electrolyte;   the multilayer material forming the anode;   
       wherein said multilayer material comprises a layer of active lithium between a metal protective layer and a nonmetallic protective layer, consisting essentially of a material selected from ceramics of the LIPON type, ionic glasses, conducting polymers, polymers containing ceramic fillers, and polymers made conducting by the addition of a solution of an ionic compound in a liquid solvent, the nonmetallic protective layer being in contact with the electrolyte. 
     
     
         18 . The generator as claimed in  claim 16 , wherein it comprises at least one assembly comprising the following elements, in the order indicated:
 a collector;   a cathode material;   a polymer electrolyte;   the multilayer material forming the anode;   an electrolyte;   a cathode;   a collector;   
       wherein said multilayer material comprises a layer of lithium between two protective layers, each consisting essentially of, independently of one another, a material selected from LIPON, ionic glasses, conducting polymers and polymers containing ceramic fillers, and polymers made conducting by the addition of a solution of an ionic compound in a liquid solvent. 
     
     
         19 . The generator as claimed in  claim 16 , wherein the lithium film of the multilayer is in contact with a nickel or copper support which serves as a current collector.