Sea urchin-like NiCoO2@C nanocomposites for Li-ion batteries and supercapacitors

Abstract

The rational construction of battery electrode architecture that offers both high energy and power densities on a gravimetric and volumetric basis is a critical concern but achieving this aim is beset by many fundamental and practical challenges. Here we report a new sea urchinlike NiCoO 2 @C composite electrode architecture composed of NiCoO 2 nanosheets grown on hollow concave carbon disks. Such a unique structural design not only preserves all the advantages of hollow structures but also increases the packing density of the active materials. NiCoO 2 nanosheets grown on carbon disks promote a high utilization of active materials in redox reactions by reducing the path length for Li + ions and for electron transfer. Meanwhile, the hollow concave carbon not only reduces the volume change, but also improves the volumetric energy density of the entire composite electrode. As a result, the nanocomposites exhibit superior electrochemical performance measured in terms of high capacity/capacitance, stable cycling performance and good rate capability in both Li-ion battery and supercapacitor applications. Such nanostructured composite electrode may also have great potential for application in other electrochemical devices.

Hierarchical NiCoO2 Nanosheets Anchored on Hollow Carbon Spheres for High‐Performance Lithium‐Ion Battery Anodes

“…[42] Simultaneously,t he main reductionp eaks are shifted to higherp otentials at 0.79 V and 1.67 V, suggesting the existence of ap ossible activation process initially and the inactivation of the NiCoO 2 duringt he first cycle. [43][44][45] During the next anodic loops, two peaks appear at 1.57 Vand 2.35 V, which representst he oxidation of metallicN ia nd Co to NiO and CoO. [46,47] The electrode reactions can be explained by Equations (1)-(3), which correspond to the cyclic voltammetry resultsa nd as imilar reaction reported previously.…”

“…During the first cathodic cycle, an obvious peak can be seen around 0.44 V, indicating the reduction of Ni 2+ and Co 2+ to Ni and Co metal with the formation of a solid electrolyte interphase (SEI) . Simultaneously, the main reduction peaks are shifted to higher potentials at 0.79 V and 1.67 V, suggesting the existence of a possible activation process initially and the inactivation of the NiCoO 2 during the first cycle . During the next anodic loops, two peaks appear at 1.57 V and 2.35 V, which represents the oxidation of metallic Ni and Co to NiO and CoO .…”

Spatially Self‐Confined Formation of Ultrafine NiCoO2 Nanoparticles@Ultralong Amorphous N‐Doped Carbon Nanofibers as an Anode towards Efficient Capacitive Li+ Storage

“…To evaluate whether the as-prepared products would be applicable as anode materials forL IBs, the electrochemical properties of NCO@ANCNFsw eref irst investigated by CV.F igure4a shows the initial three CV cycles of the NCO@ANCNFse lectrode at as can rate of 0.1 mV s À1 over av oltage range of 0.01-3.0 Vv ersus Li/Li + .N otably,i nt he first cathodic sweep,t he intense peak at 0.32 Vc an be ascribed to the reduction of Ni 2 + and Co 2 + to metallicN ia nd Co, respectively,w hich coincides with the reportedl iterature. [8][9][10][11] In the followinga nodic sweep, two oxidation peaks at 1.2 and 2.2V can be attributed to the oxidation of Ni 0 to Ni 2 + and Co 0 to Co 2 + ,r espectively.I nt he subsequentc ycles,t he reduction peaks becomem uch weaker and positivelys hift to approximately 1.14 V, and no obvious change in the potentials for the oxidation peaks in the CV curves is observed, which suggests good stability and cyclability of the hybrid electrode for the insertion/extraction of lithium ions. On the basis of the CV data and well-established storage mechanisms of NiO and CoO, [43][44][45] the entire electrochemical process can be reasonably described as Equations (1)-(3): Figure 4b shows selected charge/discharge plots of the NCO@ANCNFs electrode for the 1st, 2nd, 5th, 10th, 20th, 50th, and 100th cycles at ac urrent density of 200 mA g À1 in the voltage range of 0.01-3.0V(vs. Li/Li + ).…”

“…2019, 25,863 -873 www.chemeurj.org 100 mA g À1 again after high-rate charge/discharge at 2000 mA g À1 ,a na verage dischargec apacity as high as 627.6 mA g À1 is still recovered for the NCO@ANCNFs, which thereby impliese xtremelyd urable high-rate capability of NCO@ANCNFs. The reversible capacity of NCO@ANCNFs is comparable to or even higher than those recently reported for some other NCO-based composites with even higherN CO loadings, such as NiCo-NCO/carbon xerogel ( % 43.0 wt %; % 696 mA h À1 g À1 at 100 mA g À1 ), [11] NCO/carbonx erogel (> 43.0 wt %; % 518.0 mA h À1 g À1 at 100 mA g À1 ), [11] NCO/reduced graphene oxide/NCO ( % 86.5 wt %; % 880.0 mA h À1 g À1 at 100 mA g À1 ), [10] and NCO/amorphous carbon NTs( % 68.0 wt %; 1061.0 mA h À1 g À1 at 100 mA g À1 ). [14] More impressively,t he NCO@ANCNFs electrode without conducting CB (Figure 4c) still exhibits satisfactory rate capability coupled with ah igh CE value of about 100 %a tt he same currentd ensities.…”

“…[3,6] ParticularlyN i-Co-based mixed oxides have attracted much attention,thanks to their better electronic conductivity and richer redox reactions comparedt ot heir single-phase counterparts. [3,7] Face-centered cubic NiCoO 2 (NCO)h as recently stood out from Ni-Co-based mixed oxides as an emerging anode candidate, [8][9][10][11] beside the well-known spinel NiCo 2 O 4 . [3,12] However,c ubic-phase NCO has rarely been researched as anode for LIBs (fewer than ten contributions in the literature).…”