Improving the cycle life of cryptomelane type manganese dioxides in aqueous rechargeable zinc ion batteries: The effect of electrolyte concentration
Improving the cycle life of cryptomelane type manganese dioxides in aqueous rechargeable zinc ion batteries: The effect of electrolyte concentration
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DOI：
10.1016/j.electacta.2019.03.093
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发表时间：
2019-05
影响因子：
6.6
通讯作者：
A. Poyraz;Josh Laughlin;Z. Zec
中科院分区：
文献类型：
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作者：
A. Poyraz;Josh Laughlin;Z. Zec
可充电水性锌离子电池具有锌丰度高、成本低等优点，并且在水性电解质中具有更安全的电池化学性质。隐黑烷型二氧化锰（α-MnO2s）具有较高的理论容量、电压和丰度，是极有前途的ZIBs阴极。然而，α- mno2在电池经过长时间的充放电循环后，会遭受严重的容量衰减。本研究表明，当znso4浓度低于0.2 M时，α- mno2的恒流循环性能显著提高。在长时间电池循环测试中，低电解质浓度显示出更高的放电容量和容量保留。在0.1 M ZnSO4条件下，α- mno2在第1次和第100次循环时的容量分别为62和103 mAh/g，速率为0.3 A/g（保留率为166%）。当充放电倍率为0.9 a /g时，α- mno2在500次循环时的容量为85 mAh/g，与0.1 M ZnSO4相比，保留率提高了167%。另一方面，在高电解质浓度（>1.0 M）下，100次循环后的容量保留率低于30%，放电容量低于60 mAh/g。α- mno2在低电解质浓度下具有较好的电化学性能，主要是由于抑制了阴极溶解，减缓了znmn2o4和ZnMn3O7·xH2O等杂质相的形成。
Rechargeable aqueous zinc ion batteries (ZIBs) have many advantages such as high abundance and low cost of Zn, as well as safer battery chemistry in aqueous electrolytes. Cryptomelane-type manganese dioxides (α-MnO2s) are promising cathodes for ZIBs due to their high theoretical capacity, voltage, and abundance. However, α-MnO2suffers from severe capacity fading as the battery is put through extended charge-discharge cycles. Here, we show that galvanostatic cycling performance of α-MnO2can significantly be improved at ZnSO4concentrations below 0.2 M. Low-electrolyte concentrations demonstrated higher discharge capacities and capacity retentions at long battery cycling tests. At 0.1 M ZnSO4, α-MnO2delivered 62 and 103 mAh/g capacities with 0.3 A/g rate at the 1st and 100thcycles, respectively (166% retention). At a higher charge/discharge rate of 0.9 A/g, α-MnO2delivered 85 mAh/g capacity at the 500thcycle, where the retention was 167% with respect to the 1st cycle in 0.1 M ZnSO4. On the other hand, at high electrolyte concentrations (>1.0 M), the capacity retentions were below 30% and discharge capacities were below 60 mAh/g after 100 cycles. Better electrochemical performance of α-MnO2at low electrolyte concentrations is attributed to the suppression of cathode dissolution and the mitigation of the formation of impurity phases such as ZnMn2O4and ZnMn3O7·xH2O.