Our calculations suggest that, in 𝛿-MnO 2 , the full 2-electron Mn redox can be accessed topotactically with Al 3+ at high voltage. Similarly, R and λ-MnO 2 can achieve close to the full 2electron redox. While batteries with Al 3+ shuttle mechanisms may suffer from poor kinetics owing to strong electrostatic interactions between Al 3+ cations and anions in the electrolyte or in the MnO 2 framework, strategies like vacancy engineering and electrolyte tuning may be able to overcome these limitations. The high theoretical energy densities predicted by our calculations merit further investigation.