In Star Wars Episode II, battling with Count Dooku Yoda was. Force Lightning against Yoda Dooku uses. The lightning from affecting him Yoda stops. Then Force Lightning back at Count Dooku he uses.
Using Force Lightning was Yoda or Count Dooku's Lightning back at him just reflecting?
Reflecting Dooku's Force Lightning Yoda was. To generate his own, fall to the Dark Side he must. Absorb and reflect he can, as a great master of the Light Side.
Requested, a citation has been. Point to Wookiepedia I can, for strong in the source are their articles. The film itself, their reference is. The novelization possibly more detail contains. Force Lightning only Sith wield, at least in G-canon. Force Lightning also some Jedi wield, in lesser-canon tales.
...its use was viewed as inherently corrupting, and most Jedi Councils forbade its use.
The very short answer is that Yoda is certainly theoretically capable of casting Force Lightning, but to do so would require a 360° rethink of his Light Side philosophy. Basically he would need to discard a lifetime of Jedi teachings and become a Sith before he could do it.
The StarWars.com website notes that Force Lightning is a specifically dark side power, one that requires the user draw on anger and hatred to disfigure the Living Force enough to draw raw energy from the Force itself. Yoda and Mace (and Luke) are said to be capable of deflecting it, but there's no indication that they can generate it:
FORCE LIGHTNING
Force lightning is a dark side ability used to torture, disfigure, and even kill one’s victims. Blue in color, Sith shoot Force lightning from their hands by calling on their hatred and aggressive feelings. However, while a deadly weapon, it is not unstoppable. Force lightning can be deflected and absorbed by a lightsaber, and select Jedi have proved able to neutralize the technique through the power of the light side. - Star Wars Databank: Force Lightning
and
Palpatine raised his spidery arms toward Luke: blinding white bolts of energy coruscated from his fingers, shot across the room like sorcerous lightning, and tore through the boy’s insides, looking for ground. The young Jedi was at once confounded and in agony — he’d never heard of such a power, such a corruption of the Force, let alone experienced it. - Star Wars: Return of the Jedi - Official Novelisation
Shooting force lightning would defeat the object of what it means to be a Jedi. If you belive in the butterfly effect a tru master of Tai Chi is someone who can take the agression of others and reflect it back to achieve peace, even if it means reflecting it directly towards the attacker as the fastest means of achieving this outcome. Yoda could easily summon force lightning but at most it would be to cook his breakfast not at all to inflict harm, the path to the dark side this is.
