La 2 O 3 doped hollow porous Ni/NiCo 2 O 4 /C microspheres (NCO-La) are prepared by solvothermal method. The doping of porous La 2 O 3 nanoparticles is crucial to reduce the crystalline grain size of NiCo 2 O 4 and the internal resistance of the electrode, which facilitates ionic and electronic transportation efficiency. Hollow porous NCO-La microspheres with carbon networks have good mechanical strength and can effectively suppress volume expansion and aggregation. The combination of high-conductivity carbon and metallic nickel improves electronic conductivity. The nanostructure in the composite microspheres brings abundant active sites, which facilitates rapid redox of metal ions and allows rapid insertion and removal of Li + , consequently effectively improving the specific capacity. Benefiting from the synergy of well-designed nanostructure, the material shows high Li + storage performance and good stability. At 0.2 A g −1 after 250 cycles, the discharge specific capacity of NCO-La0.1 (1596.2 mAh g −1 ) is far better than NiCo 2 O 4 (655.6 mAh g −1 ) without La 2 O 3 doping. Such design concept of nanostructures provides a promising way to develop high-performance anode materials for LIBs.
Lei Yang,Weina Jiang,Xinyu Wang,Wancheng Ren,Huanlei Wang
Structural design and heteroatom doping of hard carbon are crucial strategies for enhancing their potassium-ion storage performance. Herein, fluorine-doped hollow porous hard carbon spheres (FHCS) are synthesized via an in-situ template coupled with fluorination strategy. The hollows carbon spherical architecture of FHCS provides abundant porosity and defects for potassium-ion adsorption while effectively mitigating volume expansion during K + insertion/extraction. Moreover, the high-content doping of fluorine element further increases the defect density of FHCS. These characteristics guarantee that the FHCS anode exhibits a predominantly adsorption-driven K + storage mechanism, contributing 81.8 % of the total capacity at 1.0 mV s −1 . As a result, the FHCS anode delivers exceptional reversible capacity (381 mAh g −1 at 0.1 A g −1 ), outstanding rate capability (194 mAh g −1 at 10 A g −1 ), and remarkable cycling stability of 83.8 % capacity retention after 3000 cycles. Furthermore, the potassium-ion hybrid capacitor assembled with FHCS anode exhibits high energy density (104 Wh kg −1 ). This study provides an effective strategy for the rational design of hard carbon and the advancement of high-performance K + storage.
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