Defect Promoted Capacity and Durability of N‐MnO_2–x Branch Arrays via Low‐Temperature NH₃ Treatment for Advanced Aqueous Zinc Ion Batteries

Abstract

Defect engineering (doping and vacancy) has emerged as a positive strategy to boost the intrinsic electrochemical reactivity and structural stability of MnO2‐based cathodes of rechargeable aqueous zinc ion batteries (RAZIBs). Currently, there is no report on the nonmetal element doped MnO2 cathode with concomitant oxygen vacancies, because of its low thermal stability with easy phase transformation from MnO2 to Mn3O4 (≥300 °C). Herein, for the first time, novel N‐doped MnO2–x (N‐MnO2–x) branch arrays with abundant oxygen vacancies fabricated by a facile low‐temperature (200 °C) NH3 treatment technology are reported. Meanwhile, to further enhance the high‐rate capability, highly conductive TiC/C nanorods are used as the core support for a N‐MnO2–x branch, forming high‐quality N‐MnO2–x@TiC/C core/branch arrays. The introduced N dopants and oxygen vacancies in MnO2 are demonstrated by synchrotron radiation technology. By virtue of an integrated conductive framework, enhanced electron density, and increased surface capacitive contribution, the designed N‐MnO2–x@TiC/C arrays are endowed with faster reaction kinetics, higher capacity (285 mAh g−1 at 0.2 A g−1) and better long‐term cycles (85.7% retention after 1000 cycles at 1 A g−1) than other MnO2‐based counterparts (55.6%). The low‐temperature defect engineering sheds light on construction of advanced cathodes for aqueous RAZIBs.

Introducing Oxygen Defects into Phosphate Ions Intercalated Manganese Dioxide/Vertical Multilayer Graphene Arrays to Boost Flexible Zinc Ion Storage

“…Figure 3c depicts the Raman spectra of pristine MnO 2 @VMG and P‐MnO 2‐ x @VMG arrays, both of which contain three characteristic peaks of the birnessite‐type MnO 2 previously reported at 490–510, 575–585, and 625–650 cm −1 . For MnO 2 @VMG sample, Raman bands located at 567 and 640 cm −1 come from the stretching vibration of MnO 6 groups of δ‐MnO 2 , while the band at 502 cm −1 is attributed to the stretching vibration of Mn‐O band . Interestingly, the Raman peak at 636 cm −1 for P‐MnO 2‐ x @VMG sample exhibits obvious shift to a lower wave number compared to the MnO 2 @VMG sample, probably caused by the introduction of oxygen defects .…”

Defect Engineering in Manganese‐Based Oxides for Aqueous Rechargeable Zinc‐Ion Batteries: A Review

“…Zhang et al reported N‐doped MnO 2– x branch arrays containing rich oxygen vacancies synthesized using a simple NH 3 treatment at low‐temperature (200 °C) condition. [ 104 ] Benefiting from the high electronic conductivity, increased electron density and contribution from surface capacitive effects, the obtained materials showed rapid reaction kinetics, high capacity at 0.2 A g −1 (285 mAh g −1 ), and an ultralong cycling performance at 1 A g −1 (85.7% over 1000 cycles) as compared to other MnO 2 ‐based materials (55.6%) (Figure 12b).…”

“…Reproduced with permission. [ 104 ] Copyright 2019, Wiley‐VCH. c) Structure of polyaniline‐intercalated MnO 2 nanolayers and their rate performance.…”

Flexible Zn‐ion batteries based on manganese oxides: Progress and prospect

“…Recently, in addition to the generation of cation deficiencies, extraction of oxygen anions can form oxygen defects to accelerate the reaction kinetics, improve the capacity, and increase long‐term cycles through NH 3 treatment, phosphate intercalation, or other treatments 72,91,114 . The intercalation of Zn ion in ZnMn 2 O 4 can be promoted by partial reduction of the Mn 3+ to Mn 2+ 105 .…”