According to the Sword Art Online Wiki, the battle (called the "Crusade") happened in August of 2024:
By August 2024, they had already killed hundreds of players, thus they were now the number one threat against the Clearers. The Clearers tried to negotiate with them via messengers, but the guild killed every one that they sent. After realizing that they would never stop killing and finding out the location of the guild's headquarters from a member of the guild, the clearers formed a high-level crusade party to wipe the guild out. Fifty high-leveled players (including Kirito and Asuna) went to attack them, however, just before they reached the designated location, the Laughing Coffin members were warned about the incoming party, so they decided to ambush the crusaders instead. Although some of the crusaders were unable to kill the red players, as the guild would not yield, some of the crusaders finally took the initiative of finishing off the Laughing Coffin members. At the end of the battle, twenty-one Laughing Coffin members and eleven crusaders had died, with most of the remaining Laughing Coffin members, including XaXa and Johnny Black, being arrested by the clearers and sent to the Black Iron Palace prison. Somehow, PoH was not found in the list of deceased or captured members, making him the only one to escape the crusade.
This was 1 month before Kuradeel was invited into the Laughing Coffin guild:
Although the guild was vanquished during the crusade, PoH, who avoided the crusade, watched Kirito and Kuradeel's duel on the 74th Floor. After hearing that Kuradeel wished to kill Kirito, after the duel and before Kirito went to a mandatory training session with Kuradeel and Godfree, PoH approached Kuradeel. PoH then invited Kuradeel to his guild and taught him how to make paralysis poison.
Here's a full Timeline. It says the battle happened after the "Warmth of the Heart" light novel volume and that by August, they were on the 70th floor. So I think that would put the battle somewhere between episodes 7 and 8?