On this day in aviation history, a Boeing 787, registered N1791B and already in the colours of its future owner LOT Polish Airlines (to become SP-LRC), completed the test program to certify the new lithium-ion battery system. This concluded the test program for proving battery system operation under normal and abnormal situations. The results of this test program were submitted to the FAA, which led to lifting the flight ban of the B787 later that month. One of the changes to the battery system of the Boeing 787 was the addition of ceramic insulation to prevent a thermal runaway of the battery (Thermal runaway is a condition where the current flow through a battery cell causes the temperature of the cell to rise, which will lead to a further rise in temperature). The following picture from Boeing details the changes made to the lithium-ion batteries:
Another change was the installation of the battery in the aircraft, the batteries were now, for all intents and purposes, installed outside the pressure hull of the aircraft. They were still installed in their respective locations in the aircraft, however in a sealed vessel that is connected to outside of the aircraft. And thus preventing potential smoke or fumes from the battery from entering the cabin.
More information can be found on the Boeing website.