Two advantages by a single move : core-bishell electrode design for ultrahigh-rate capacity and ultralong-life cyclability of lithium ion batteries

Abstract

Developing efficient electrodes with superior rate performance and superb cyclability are highly desired for meeting urgent demand of high-energy and large-rate lithium ion batteries (LIBs). Electrochemical performance of popular transition metal oxide electrodes is severely restricted by its inferior structure stability and low conductivity, leading to rapid capacity fade at high current density or deep cycling. Herein, a unique 3D core-bishell (3D-CBS) nanoporous electrode with configuration of Cu (NPC) core and bi-layered conformal Cu2O@PANI shells was dedicatedly designed and built by a novel and cost-effective approach combining chemical dealloying with controlled electro-polymerization. The 3D-CBS nanoporous electrodes deliver a large reversible capacity of 349 mAh g−1 at 6000 mA g−1 after 11500 ultralong-cycles with 76% capacity retention, corresponding to only 0.002% capacity fade per cycle. The superb cyclability is related to the unique 3D-CBS electrode design and in-situ formation of Cu2O with exposed most Cu+ (Cu+/O2− = 4/1) and low-energy (111) crystal plane (0.046 eV/Å2) on NPC matrix, as confirmed by physicochemical characterization and DFT calculation. Impressively, the 3D-CBS electrode displays superior rate capability with negligible capacity fade after 5 multistep-rate periods from 2 up to 20 A g−1 and back again to 2 A g−1 repeatedly (over 400 cycles), which is ascribed to the conformal coating of PANI as protective nanolayers with good conductivity on Cu2O, achieving ultrafast Li+ diffusivity (DLi = 2.42 × 10−10 cm2 s−1) and significantly improved electron conductivity (82000 S m−1). We believe that this work provides novel insights for design and synthesis of ultrahigh-rate and ultralong-life nanostructured anodes toward advanced LIBs.