Increasing demands for higher energy density batteries have inspired multi-electron cathodes which can double the energy density per transition metal cation. In Li-ion batteries, vanadyl phosphates have been shown to intercalate 2 Li⁺ per V center by activating V^4+/5+ and V^3+/4+ redox couples, resulting in a gravimetric capacity of 305 mAh g⁻¹. In order to employ the VOPO₄ structure in earth abundant and cheaper alkali-ion batteries, channels must be expanded to allow the diffusion of larger cations. This can be achieved by pillaring the VOPO₄ framework with large cations. KVOPO₄ has been shown to be a high capacity cathode in Na-ion batteries, however not all of the K could be removed from the structure, limiting the accessible capacity. NH₄VOPO₄ is similar to KVOPO₄ where the KTP-type VOPO₄ framework is enlarged and distorted due to the presence of large cations. In this study, we investigate the electrochemical performance of NH₄VOPO_4. While the pristine material suffers greatly from parasitic reactions, we show that electrochemistry and thermal stability can be improved by exchanging some of the NH₄ ⁺ with Na⁺.