Layered MnO2 is regarded as one of the most prospective cathode materials for aqueous zinc-ion batteries (AZIBs), yet it is impeded by its inferior conductivity and the poor cycling stability caused by the manganese dissolution. Herein, a facile alkali-metal-ion intercalation strategy is proposed, where sodium ion and potassium ion are adopted to verify the universality of the alkali-metal-ion intercalators in promoting the zinc-ion storage capability of MnO2. The intercalated alkali-metal ions could not only effectively promote the structural stability by serving as pillars but also improve the conductivity by modulating its electronic structure. Moreover, the extra oxygen defects are introduced during the intercalation of alkali-metal-ion “pillars”, which is conducive to the mitigation of manganese dissolution by regulating the Mn–O bond and acceleration of Zn2+ kinetics. As a result, the proposed Na+-intercalated MnO2 (NMO) and K+-intercalated MnO2 (KMO) present enhanced electrochemical performances and Zn2+ transfer kinetics. Specifically, NMO 600 and KMO 650 deliver the capacities of 236.3 and 158.2 mAh g–1 after 100 cycles at 0.1 A g–1, respectively, which are larger than that of pristine δ-MnO2. This work substantiates the potential of alkali-metal-ion “pillars” in improving the zinc-ion storage capability of layered MnO2 cathode and provides a promising way to develop high-performance manganese-based cathode materials via a facile solid-phase method.
Denglei Zhu,Yufan Zheng,Yi Xiong,Chaojun Cui,Fengzhang Ren,Yong Liu
Aqueous rechargeable zinc-ion batteries (AZIBs) have gained extensive attentions due to their high volumetric capacity, low cost, and intrinsic safety. Nonetheless, their zinc metal anodes have been suffered from many issues, such as uncontrollable dendrite growth and undesired side reactions, which eventually degrade the capacity and cycle life. Herein, a thin sulfur-doped zinc oxide artificial interface film (≈200 nm) was in situ grown on zinc foil (ZnO:S@Zn) by a simple chemical bath deposition method. The density functional theory calculations revealed that the electronic conductivity of zinc oxide could be improved after sulfur doping. Characterization analyses and electrochemical measurements showed that this unique film could enhance the electrical conductivity of zinc anode inhibit the side reaction and induce Zn 2+ uniform deposition. As a result, the ZnO:S@Zn symmetric cell was stably cycled for 1700 h at 0.5 mA cm −2 with a stable voltage hysteresis of ~20 mV, and the full-cell pairing with MnO 2 cathode exhibited an excellent reversible capacity of 297.46 mAh g −1 after 300 cycles. This work offers a simple and effective way to fabricate a stable Zn metal anode for high performance AZIBs.
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