Surfaces/Interfaces Modification for Vacancies Enhancing Lithium Storage Capability of Cu₂O Ultrasmall Nanocrystals

Abstract

Theoretically, Cu2O delivers a poor Li storage capacity ∼373.9 mA h g–1 based on a so-called conversion reaction (Cu2O + 2Li → 2Cu + Li2O). Herein, we broke through the bottleneck and acquired an impressive lithium storage capability (1122 mA h g–1) tripled more than the theoretical one by an in situ surface/interface engineering process for the first time. The surface/interface modification enabled us to fabricate ultrasmall nanocrystals of Cu2O with Cu vacancies (VCu) of high concentration, somewhat like monovalent anion doping. Except for the conversion reaction-type capacity, VCu enhancing intercalation pesudocapacitance in Cu2O and its reduction product-Cu also contributed a lot to the Li-storage capability. First-principles calculation substantiated that intercalation energy of Li was severely lowered for both Cu vacancy-rich Cu2O and Cu comparing with their stoichiometric counterparts. Another important factor for the enhancement was the surface/interface organic species themselves which could reversibly store Li by redox reactions. The surface/interface modification for vacancies, vacancy inheritance from metal oxide to single metal, and vacancy-enhancing Li-storage capability in metal oxide and single metal all will inspire us a lot in fabricating new-generation advanced electrodes for rechargeable batteries.

Multiple Active Sites: Lithium Storage Mechanism of Cu‐TCNQ as an Anode Material for Lithium‐Ion Batteries

“…The cathodic peaks at 2.35 and 2.15 V shift to higher potential and the integral areas of these peaks along with anodic peak at 3.0 V shrink, caused by the dissolution of TCNQ x− , as reported previously . An unnoticeable anodic peak at 1.6 V in the first three scans remains after 100 cycles, which might be caused by pesudocapacitance similar to Cu‐vacancy formed in Cu 2 O ultra‐small nanocrystals …”

“…[35,36] In the discharge/charge cycle test, Cu-TCNQm ight evolvei nto ultra-small nanocrystals, and the enhanced organic surfaces/interfaces along with pseudocapacitancem ight cause the rising tendency of cycling. [34,37] As ac ontrast, the specific capacityo fC u-TCNQ between 0.2-3.0 Vd ecreased to almost zero in the first 7s cans ( Figure S1). The relatedr esearch work is still in progress.…”

“…[22,23] An unnoticeable anodicp eak at 1.6 Vi nt he first three scans remains after 100 cycles,w hichm ight be caused by pesudocapacitance similar to Cu-vacancy formed in Cu 2 Ou ltra-small nanocrystals. [34] The cycling performance of Cu-TCNQ/Cu was measured in a voltager ange of 0.01-3.0 Va nd compared with Cu-TCNQ powder ( Figure 3b). The initial discharge and charge specific capacityo fC u-TCNQ/Cus elf-supported electrode is 373.4, 219.4 mAh g À1 respectively,c orresponding to an initial coulombic efficiency of 58.8 %.…”

Current Status and Challenges of Calcium Metal Batteries

“…[ 2,22–27 ] Hence, the future trends in cathode materials lie in not only achieving cycling stability and long lifespan of S and sulfides, [ 28,29 ] layered metal oxides, [ 30 ] and polyanionic phosphates but also developing multicomponent high‐voltage or Ca‐rich large capacity cathodes such as Ni/Mn‐based Li/Na‐counterparts and defect/interface‐engineered fast kinetics and cycling‐stable cathodes. [ 31–36 ]…”

The Principle of Introducing Halogen Ions Into β-FeOOH: Controlling Electronic Structure and Electrochemical Performance

“…However, how to realize the modification of material electronic structure by incorporation of anions is rarely reported and an urgent task needs to be addressed and resolved [29]. As a matter of fact, because of the convenient operation and unique modulate manner of anions for host materials, forming coordination bonding, the host materials can produce abundant vacancies and keep the integrity of crystal structure well; thus, they exhibit excellent performances [30][31][32][33].…”