Enhanced sodium storage property of copper nitrate hydrate by carbon nanotube

• Cu(NO3)2·2.5H2O is studied for the first time for sodium storage.
• Cu(NO3)2·2.5H2O/CNT is prepared by a simple solution route.
• Cu(NO3)2·2.5H2O/CNT presents a sodium storage capacity of 1217.5 mAh g− 1.
• The cycling property of Cu(NO3)2·2.5H2O can be effectively enhanced by CNT.

In this work, novel nano/micro structure nitrates are reported for sodium storage for the first time. By using a facile solution route, carbon black (CB) and carbon nanotube (CNT) are introduced to incorporate with copper nitrate hydrate (Cu(NO3)2·2.5H2O) to form Cu(NO3)2·2.5H2O/CB and Cu(NO3)2·2.5H2O/CNT composites for high capacity sodium storage, respectively. Morphological and structural investigations show that CB or CNT coating does not obviously change the particle size and phase composition of Cu(NO3)2·2.5H2O, while, the electrochemical performance of Cu(NO3)2·2.5H2O is significantly improved by introducing CB or CNT as a conductive network. Moreover, carbon matrix can also provide a buffer for suppressing particle pulverization during sodiation/desodiation process. Especially for CNT, it builds a three-dimensional conductive network for active particles. As a result, Cu(NO3)2·2.5H2O/CNT exhibits higher reversible specific capacity and better cycling stability than bare Cu(NO3)2·2.5H2O and Cu(NO3)2·2.5H2O/CB. After 30 cycles, Cu(NO3)2·2.5H2O/CNT can deliver a reversible charge capacity of 140.7 mAh g− 1 at a current density of 50 mA g− 1. This result demonstrates that CNT reinforced Cu(NO3)2·2.5H2O composite could be a probable anode material for sodium-ion batteries. Besides, the probable sodium storage mechanism in Cu(NO3)2·2.5H2O is also proposed by using various ex-situ analytical methods.

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