Low-Cost, Long-Cycle-Life Sodium-Ion Battery to Enable Grid Scale Energy Storage

Large-capacity, cost-effective energy storage is the transformational technology needed to enable large scale integration of renewable energy (e.g. wind, solar). The rechargeable battery offers efficient electrical energy storage (EES). The Li-ion battery has been the leading option based on its performance, but it is too expensive for large-scale EES. Unlike Li, Na is readily available worldwide and therefore much less costly than Li.

Sodium-ion batteries (SIBs) based on a hexacyanometallate (HCM) cathode are good options for the purpose of a low cost battery for EES. These materials correspond to the general chemical formula, A_xM₁[M₂(CN)₆]_y·zH₂O, consisting of a cubic framework with cyanide (C≡N)^- ligands bridging metal-ions, M₁ and M₂, thus forming large lattice interstitial spaces to facilitate efficient alkali-ion, “A”, intercalation. Electronic configurations of M₁ and M₂ are strongly affected by the cyanide ligands. In particular, ligand field splitting energy is higher for M₂-ions associated with carbon than for M₁-ions associated with nitrogen, which results in a low spin (LS) electron configuration for M₂, but a high spin (HS) electron configuration for M₁.

We will present our study on HCM-based cathode materials, including their bulk and surface structures as well as their electrochemical performance. We will demonstrate that the HCM-based cathodes provide promising low-cost and long-cycle life SIBs of high specific energy density and efficient EES.

References:

1. Long Wang, Yuhao Lu, Jue Liu, Maowen Xu, Jinguang Cheng, Dawei Zhang, and John B. Goodenough. Angew. Chem. Int. Ed., 2013, 52, 1964 –1967.

2. Yuhao Lu, Long Wang, Jinguang Cheng and John B. Goodenough. Chem. Commun., 2012, 48, 6544–6546.