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[Display omitted] • An in-situ confined growth of Cu 2-x Se nanoparticles in highly defective carbon is proposed; • Cu 2-x Se undergoes intercalation and reversible intermediate phases transformation during cycling; • Intercalation of Na+ can improve the electrical conductivity and rate performance of Cu 2-x Se@NC; • Cu 2-x Se@NC shows high reversible capacity, superior rate performance and long-cycle durability. Transition metal selenides are considered as hopeful anode materials for sodium-ion battery (SIB) due to the high specific capacity and rich reserves in nature. However, the inherent low conductivity of these anode materials, as well as the inevitable volume expansion and structural collapse during cycling, result in their poor rate performance and cycling stability. Herein, a universal selenization-co-carbonization strategy is proposed to synthesize Cu 2-x Se nanoparticles in-situ confined in highly defective nitrogen-doped carbon (Cu 2-x Se@NC) with superior architectural features, which involves simultaneous selenization and carbonization procedure of octahedral metal–organic framework (Cu-BTC) precursor. The nitrogen-doped carbon matrix stabilizes/confines the Cu 2-x Se nanoparticles to prevent their agglomeration and volume expansion during cycling while endowing high electrical conductivity to the hybrid materials. As anode for SIBs, the Cu 2-x Se@NC exhibits a high reversible capacity of 340 mAh/g at 0.1 A/g with a high initial coulombic efficiency of 70 %, superior rate performance (capacity retention of 82.4 % from 0.02 to 5 A/g), and long-cycle durability. The ex-situ XRD and HRTEM techniques confirmed that Cu 2-x Se undergoes complex intercalation and crystal evolution accompanied by reversible intermediate phases (NaCuSe and Na 2 Se) transformation during charge/discharge cycle. First-principles calculations and in-situ EIS confirmed that the intercalation of Na+ can greatly reducing the energy band gap and improving the electrical conductivity of Cu 2-x Se@NC, thereby achieving excellent rate performance. Moreover, the Cu 2-x Se@NC anode is also evaluated by matching with Na 3 V 2 (PO 4) 3 cathode to assemble a full SIB, which can provide high initial capacity and capacity retention, revealing its potential for practical application. [ABSTRACT FROM AUTHOR]

[Display omitted] • The Cl-doped ZIF-67-derived carbon microspheres were prepared by a novel chlorination method in high-temperature. • The electrochemical performance of CCH@CM has been greatly improved compared to ZIF-67. • CCH@CM continues the microporous structure of ZIF-67 while minimizes volume expansion. • Cobalt Chloride Hydrate (CCH) grown in situ provides maximum active sites for electrochemical reactions with Li-ions. In this work, the carbon-microsphere loaded with cobalt chloride hydrate (CCH@CM) was prepared via a collaborative and chlorination strategy derived from ZIF-67 precursor, which exhibits a superior electrochemical performance as a lithium-ion battery anode material. The synthesized CCH@CM obtained a high initial discharge capacity (947 mAh g−1) and the capacity attenuation rate is close to zero after 200 cycles at the current density of 100 mA g−1. The porous structure derived from ZIF-67 not only can provide a conductive path, which increases the transport of electrons and lithium ions, but also alleviate volume expansion. The presences of -Cl-/H 2 O groups provide active sites for the anchoring of Li+. As the first successful synthesizing the cobalt chloride hydrate (CCH) from ZIF-67, good electrochemical performance provides a promising for the large-scale application in lithium ion batteries. [ABSTRACT FROM AUTHOR]