Electrode for a battery

Abstract

An electrode for a bipolar cell or battery includes a plate-like body made of hardened resin containing particles of titanium suboxide or other electrically conductive particulate arranged to form electrical paths. A method of testing the body for porosity is also disclosed.

1 . A method of making a substantially pore-free electrode, the method comprising:
 mixing an unhardened thermosettable resin, a hardener therefor, and conductive particles to provide a mix;   pouring the mix into a mold therefor; and   molding the mix to form a shaped body having electrical paths defined by the conductive particles,   wherein the conductive particles are titanium suboxides of the formula Ti n O 2n−1  where n is 4 or greater and the particles have a size distribution with a standard deviation of less than 50% of a mean particle size.   
     
     
         2 . The method according to  claim 1 , wherein up to 50% by weight of the mix comprises the resin and hardener. 
     
     
         3 . The method according to  claim 1 , wherein the mix includes a bimodal distribution of substantially uniform large particles and a proportion of smaller particles dimensioned to fit in interstices between the large particles. 
     
     
         4 . The method according to  claim 1 , wherein the mix includes a polymodal distribution of a range of particle sizes ranging from large particles to successively smaller particles dimensioned to fit in interstices between the large particles. 
     
     
         5 . The method according to  claim 1 , wherein the titanium suboxides comprise Ti 4 O 7  and/or Ti 5 O 9 . 
     
     
         6 . The method according to  claim 5 , wherein the conductive particles are first contacted with a gas for a period to extend a conductivity thereof. 
     
     
         7 . The method according to  claim 6 , wherein the gas is helium or hydrogen. 
     
     
         8 . The method according to  claim 1 , wherein the resin has a viscosity of less than about 50 Pa·s at 25° C. 
     
     
         9 . The method according to  claim 8 , wherein the resin is epoxy resin. 
     
     
         10 . The method according to  claim 1 , wherein the unhardened resin and the hardener are mixed, and the conductive particles are added to form a dough which is then added to a preheated mold. 
     
     
         11 . The method according to  claim 10 , wherein the resin, the hardener and the particles are first formed into a sheet molding compound which is added to the mold. 
     
     
         12 . The method according to  claim 11 , further comprising the step of applying foils of metal to one or both surfaces of the sheet molding compound. 
     
     
         13 . The method according to  claim 10 , further comprising the step of placing the mold in a heated press and applying pressure. 
     
     
         14 . The method according to  claim 13 , wherein the pressure exceeds 2000 Pa. 
     
     
         15 . The method according to  claim 13 , wherein the mold is heated to more than 35° C. 
     
     
         16 . The method according to  claim 15 , wherein the mold is heated to more than 70° C. 
     
     
         17 . The method according to  claim 1 , further comprising the step of removing the shaped body from the mold and cleaning surfaces of the shaped body. 
     
     
         18 . The method according to  claim 17 , wherein the method of cleaning comprises grit blasting, corona discharge treatment, application of plasmas, chemical etching, or solvent degreasing. 
     
     
         19 . The method according to  claim 1 , wherein excess resin is ejected from the mold during a step of pressing the mold. 
     
     
         20 . The method according to  claim 1 , further comprising subsequently applying a battery paste to the electrode. 
     
     
         21 . The method according to  claim 20 , further comprising the step of applying a thin layer of metal to the electrode before the paste is applied. 
     
     
         22 . The method according to  claim 21 , further comprising the step of pressing a metal foil on to a surface of the electrode while the resin is curing in the mold. 
     
     
         23 . The method according to  claim 22 , wherein the metal foil is up to 200 microns thick. 
     
     
         24 . The method according to  claim 21 , further comprising applying the layer of metal by electroplating and optionally adding dispersoids to a plating solution. 
     
     
         25 . The method according to  claim 23 , further comprising treating a surface of the metal layer with a corona discharge or a plasma. 
     
     
         26 . The method according to  claim 20 , further comprising adding a coupling and/or a wetting agent to the paste. 
     
     
         27 . A battery prepared in accordance with the method of  claim 1 . 
     
     
         28 . The battery according to  claim 27 , comprising a plurality of electrodes and an acid electrolyte.