I add an answer because I want to shade some points of the accepted answer.
First point: Soviet and Stalin's point of view on the conflict.
The accepted answer gives anachronic vision of the situation. Stalin had no clear vision of the army vs navy conflict in Japan about strategic directions where to expand. Elements supporting that point is that he never trusted his famous spy Richard Sorge when he said that the Japanese had abandoned the idea of a Siberian conquest.
Instead of a strategic calculation about Japanese internal politics, the Soviet reaction to the conflict was a simple "You shall not pass" politic: The Japanese view of Siberia were seen as the following part of the 1904-1905 war, and Stalin, for "prestige" issues (which are directly linked to being overthrown in such a regime), could not support a defeat nor any territory loss.
Second point: The fact that the conflict was not important for Japan
That is true in the idea that the Japanese army had the tendency to start conflict "on its own". But overall, the issue was not a low politic willingness to fight rather than a lack of logistic preparation and fightings in China that hampered efforts.
Third point: Barbarossa being a failure
I agree with the overall ascertainment, but this is not an argument: the targets of Barbarossa and Khalkin Gol were not of the same scale, and this is exactly the inability of the Germans to stop when they were successful that led them to disaster (+ the two fronts fighting). The Japanese, achieving in Siberia (a less developed territory so less important for USSR) a quarter of what Barbarossa achieved, would have been satisfied and started negociations.
On the other hand, I admit that there were Japanese "they will not come back" thoughts after the initial fighting in Khalkin Gol, and that this contributed to the difference of forces between Soviet and Japanese armies during the 2nd phase of Soviet counter-offensive.
I entirely endorse the other points: difference of context for Winter War and Barbarossa, good generals being still there in the Red Army and sent at Khalkin GOl (notably Jukov).