Ultrathin CuSe nanosheets as the anode for sodium ion battery with high rate performance and long cycle life

A facile synthesis of CuSe nanosheets for high-performance sodium-ion hybrid capacitors

“…1e and f ) reveal that the lattice interplanar spacings of 0.32 and 0.33 nm correspond to the (102) and (101) planes of CuSe, respectively. 17 Furthermore, the results of selected area electron diffraction (SAED) show that the CuSe nanosheets are polycrystaline in nature due to the presence of ring and dot patterns.…”

“…16,32 The strong cathodic peak at 0.87 V is due to the complete reduction of Na x CuSe, the decomposition of the electrolyte and the formation of the SEI lm. 17,33,34 In the initial charging process, the anodic peak at 1.83 V corresponds to the transformation of Cu and Na x Se to Na x CuSe, and the other three peaks at 1.83, 1.95 and 2.05 V originate from the transformation of Na x CuSe to CuSe. 16,17,35 However, the anode peaks at 1.83 and 2.05 V disappeared in the subsequent scans, indicating that some intercalation reactions are also irreversible.…”

“…17,33,34 In the initial charging process, the anodic peak at 1.83 V corresponds to the transformation of Cu and Na x Se to Na x CuSe, and the other three peaks at 1.83, 1.95 and 2.05 V originate from the transformation of Na x CuSe to CuSe. 16,17,35 However, the anode peaks at 1.83 and 2.05 V disappeared in the subsequent scans, indicating that some intercalation reactions are also irreversible. During subsequent scanning, the cathode peaks stabilize at 0.66 and 1.64 V, while the anode peaks remain at 1.48 and 1.95 V. 16,17,22 Furthermore, the CV curves from the second cycle almost overlapped, indicating good reversibility and stability during repeatable sodiation and desodiation stability in the CuSe nanosheets.…”

“…16,17,35 However, the anode peaks at 1.83 and 2.05 V disappeared in the subsequent scans, indicating that some intercalation reactions are also irreversible. During subsequent scanning, the cathode peaks stabilize at 0.66 and 1.64 V, while the anode peaks remain at 1.48 and 1.95 V. 16,17,22 Furthermore, the CV curves from the second cycle almost overlapped, indicating good reversibility and stability during repeatable sodiation and desodiation stability in the CuSe nanosheets. The possible electrochemical reactions are expressed as follows:…”

“…The reason is the high conductivity and convenient reversible conversion of the CuSe nanosheets in the electrochemical process, indicating a high utilization of the electrolyte with the electrode materials. 16,17 Although the discharge capacity at the 10th cycle is 279 mA h g À1 , it increases to 307 mA h g À1 at the 40th cycle, showing an initial decrease and then an increased process as a whole. Consistently, Fig.…”