4.28.2016

How do Tantalum Capacitors Work? REALLY. The Real reason you can't charge Tantalum electrolytic capacitors backwards

So I have been researching batteries and capacitors a lot and have realized one thing: We are bieng lied to.  Batteries and capacitors don't work like we are told or what is bieng taught in textbooks.  Only 2 things could be happening, either they know how they really work and are feeding us old outdated theories in order to protect battery makers and investors (or other industries like oil over electricity) hegemony or they simply are in the dark and have no clue about how they actually work.  I think the answer must be a mix of the two because somethings I can believe they just don't understand but others I think just have to be a blatant lie.

I think the way they explain how tantalum capacitors explode if you charge them backwards falls into the blatant lie category.  There is just no way they can be this dumb.


It would help if I explained exactly how electrolytic capacitors worked first but that is a big topic so I will just introduce it.  How do capacitors really work?  What is happening as you can see above is the anode is charged positive.  The anode is the electrode that get oxidized.  In a battery the anode is the material that is preferentially oxidized by the electrolyte.  This preferential oxidation is what causes electron release and power generation.  In a capacitor we (usually) have two of the same materials so there is no preferential oxidation of one electrode over the other and why capacitors don't generate power on their own.  In order to get preferential oxidation we have to apply a different charge on one electrode than another.  Now the positively charged electrode will preferentially get oxidized over the negatively charged electrode.  This makes sense because electrons are reducing agents so the negatively charged electrode will be reduced and the positively charged will be oxidized.  This power generation only exists while the difference of charge lasts, so that is why capacitors energy output exponentially decays while batteries do not.  Batteries don't have to maintain an electrical charge to put out power which really makes batteries a superior technology in my mind.  The only benefit to capacitors is they use physics (electric charge) as leverage instead of being purely chemical like batteries.

So we have the positive electrode being  oxidized (anode) in a capacitor and the negative reduced.  This is opposite from a battery where the negative electrode is oxidized (anode) and the positive is reduced.  What gives?  Why are they opposite?  Well they really aren't opposite, the anode is being oxidized in both cases BUT when the capacitor is charged that anode now becomes the cathode (positively charged).   This is because we positively charge the anode so it gets preferentially oxidized, but while it is getting oxidized it becomes the cathode so we can use it as positive.


Alright I know that is kind of confusing but hopefully it clears up some confusion in a lot of minds about how capacitors actually work.  So now how does this apply to tantalum capacitors and why you can't charge them backwards?  Well if as in a typical capacitor you have 2 of the same electrodes then you could charge it any way you want and it would still work. But tantalum is expensive.  Only 1 electrode is tantalum the other is probably something cheaper, lets say copper.  Now this is where they lie.  They say "oh the electrolyte is the electrode!"  How ridiculous!  No the metal the electrolyte is touching is the electrode retard.  Basic Chemistry 101 don't be stupid.  "The oxide layer is the dielectric!" they say. Someone is trying desperately to hold on to the old outdated and blatantly wrong understanding of how capacitors work.  Forget "dielectric" that word is meaningless and doesn't apply to how capacitors really work.  It is an ancient relic.  So what we really have is a tantalum electrode, and a (lets say) copper electrode separated by an electrolyte.  Cool. So why doesn't this just work as a battery?  We have two different materials right?  Right BUT in order for it to work as a battery the electrolyte must be able to oxidize ONE of the metals all by itself.  So what they do is choose an electrolyte that oxidizes NEITHER.  That way it doesn't act like a battery.  Make sense?  Now copper is the lightweight of the two and it is more easily oxidized than tantalum.  So the copper is charged negative and tantalum is positive.  Tantalum is a beast and it can handle the onslaught.  As it turns positive the electrolyte oxidizes it and forms the oxide layer.  Then when the voltage across the electrodes is released, that oxide layer acts as the cathode (positive) and the copper as the anode (negative) and it generates power like a battery as long as the charge lasts (like all capacitors do). 

So why can't we charge it in reverse?  Well its simple, copper isn't tough enough to get oxidized.  Tantalum is the most resistant metal of all (maybe excepting iridium).  Since we selected an electrolyte that was strong enough to oxidize tantalum, we can only imagine what it would do to copper if we reversed things.  If copper was positively charged and therefore got oxidized it wouldn't form a nice oxide layer like tantalum would, it would get utterly destroyed.  A hole will probably form in the copper leaking out oxidizing electrolyte which will start a chain reaction.  Or in the case of manganese dioxide/carbon electrode the manganese compound gets further oxidized which oxidizes the carbon and starts it on fire.  And that is why you can't charge electrolytic capacitors backwards.

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