Search

• The metal phosphates coated P3-NaMN is synthesized via co-precipitation route. • The modified samples show a great improvement of cycling performance. • The metal phosphates coating could promote the air stability of the materials. • The coated layer could inhibit the loss of lattice oxygen in high voltage region. Cathode materials are considered to be the most critical component of the sodium-ion batteries, which determine the overall electrochemical performance of the battery to some degree. Currently, the layered oxides receive significant attention due to the high operating voltage and high capacity. However, the instability in the air and unsatisfactory cycling performance limit their commercial application. Based on excellent electrochemical performance of the P3-type Na 0.65 Mn 0.75 Ni 0.25 O 2 material, here AlPO 4 and Mg 3 (PO 4) 2 protective coatings are employed to modify P3-type Na 0.65 Mn 0.75 Ni 0.25 O 2. The metal phosphate layers cover the surfaces of the pristine particles via a co-precipitation route. It has been found that the two modified samples exhibit an obvious improvement of cycling performance with the capacity retentions about 93% at a current density of 0.2 C within 100 cycles. In addition, the coated metal phosphate layer can effectively suppress the irreversible oxidation of oxygen in the high voltage redox region. Furthermore, after exposure to the air, the coating samples still retain a high electrochemical activity. Therefore, the metal phosphates coating provides a meaningful exploration for the research and development of long-term cycling life and high air stability of cathode materials in sodium-ion batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] • An ultralow-potential H 2 Ti 3 O 7 ·xH 2 O anode is first introduced for zinc-ion batteries. • The storage mechanism of H+ and Zn2+ co-insertion is demonstrated on the H 2 Ti 3 O 7 ·xH 2 O anode. • The H 2 Ti 3 O 7 ·xH 2 O anode features excellent electrochemical performance. • The assembled Zn x MnO 2 //H 2 Ti 3 O 7 ·xH 2 O full battery exhibits the high output voltage. Developing the alternative anode materials that can completely resolve the dendrite concern of Zn metal anodes are desirable for reliable aqueous zinc-ion batteries. However, the sub-optimal charging potentials of reported anodes inevitably cause the discounted output voltage and energy density on a zinc-ion full battery. Herein, it is firstly demonstrated that the hydrated titanic acid (H 2 Ti 3 O 7 ·xH 2 O) can be applied as an ultralow-potential anode for the aqueous zinc-ion full battery. The depressed potential (0.2 V vs. Zn2+/Zn) of the H 2 Ti 3 O 7 ·xH 2 O compared to that of reported candidates could significantly enhance the operating voltage level of the zinc-ion full battery. Furthermore, the comprehensive analyses demonstrate that the expanded lattice spacings and interlayer crystal water stimulate Zn2+ along with H+ to jointly insert and extract on the H 2 Ti 3 O 7 ·xH 2 O anode. The low-potential H 2 Ti 3 O 7 ·xH 2 O anode exhibits an impressive cycling performance and coulombic efficiency by virtue of the assistance from interlayer crystal water. The assembled Zn x MnO 2 //H 2 Ti 3 O 7 ·xH 2 O zinc-ion full battery delivers the decent electrochemical performance, especially a high output voltage of over 1 V. This low-potential, high-stable H 2 Ti 3 O 7 ·xH 2 O anode reveals the exceptional potential for aqueous zinc-ion full batteries. [ABSTRACT FROM AUTHOR]