fig2

Figure 2. (A) Typical crystal structures of polyanionic compounds. Reproduced with permission^[37]. Copyright 2018, American Chemical Society; (B) Typical crystal structures of Prussian blue analogs. Reproduced with permission^[44]. Copyright 2025, American Chemical Society; (C) Typical crystal structures of layered transition metal oxides. Reproduced with permission^[51]. Copyright 2014, American Chemical Society; (D) Key performance comparison chart of polyanionic compounds; (E) Key performance comparison chart of Prussian blue analogs (PBAs). No additional copyright attribution; (F) Key performance comparison chart of layered transition metal oxides (LTMO).