It explains it:
"But Goodenough’s battery has pure metallic lithium or sodium on both sides. Therefore, the voltage should be zero, with no energy produced, battery researchers told Quartz. Goodenough reports energy densities multiple times that of current lithium-ion batteries. Where does the energy come from, if not the electrode reactions? That goes unexplained in the paper. The unstated physics would lead to creation of a battery that, once charged, requires no further energy in order to keep pushing out electricity—violating the laws of thermodynamics."
The batteries you mentioned have DIFFERING materials on each side. This one doesn't. Hence the mystery. Sound like BS to me. If you have something, prove it.