Is the phrase "As of today, you are no longer under my charge," spoken to the wife in a moment of anger and without the intention of divorce, considered a divorce?

The phrase "she is not on my responsibility" is a form of كناية (allusion or indirect expression), and divorce does not occur through it unless the intention was to effect divorce. Since you did not intend that, there is nothing upon you, and your wife remains under your marital bond. One should avoid the causes of anger due to the harms it entails, in accordance with the Prophet's (peace be upon him) advice: "Do not get angry."