Optimized scandium doping in Al₂Mo₃O₁₂ with NP co-doped carbon coating for enhanced low-temperature lithium storage

Abstract

The development of low-temperature anode materials is crucial for the practical application of lithium-ion batteries (LIBs). Al 2− x Sc x Mo 3 O 12 ( x = 0, 0.5, 1, 1.5) materials were synthesized using a high-temperature solid-state method, and the effects of scandium doping on their structure, morphology, and electrochemical properties were investigated. Among the Sc-doped specimens, Al 1.5 Sc 0.5 Mo 3 O 12 exhibited the best performance, with an initial discharge specific capacity at −25 °C of 128.27% that of Al 2 Mo 3 O 12 , and a capacity of 122.87 mAh g −1 even after 50 cycles. This is attributed to the fact that Sc doping optimizes the material morphology and reduces the resistance to electron/lithium-ion transport. Subsequently, Al 1.5 Sc 0.5 Mo 3 O 12 (ASMO) was coated with nitrogen and phosphorus co-doped carbon (CNP) using sucrose and NH 4 H 2 PO 4 as raw materials. Based on different mass ratios of the mixtures, the resulting materials were designated as ASMO@CNP(811), ASMO@CNP(712), and ASMO@CNP(622). The results indicate that the carbon layer is well-bonded to the substrate without disrupting the original crystal structure. Moreover, N P co-doped carbon coating strategy can synergistically enhance the electronic conductivity and ionic conductivity of materials, and meanwhile optimize the charge storage mechanism. After 50 cycles at room temperature, ASMO@CNP(622) exhibited a capacity of 200.14 mAh g −1 , which is 232.67% of that of the pristine Al 1.5 Sc 0.5 Mo 3 O 12 . Even at −25 °C, it retains a high capacity of 186.59 mAh g −1 after 50 cycles. This study demonstrates that a synergistic modification strategy combining Sc doping with N P co-doped carbon coating can effectively enhance the low-temperature lithium storage performance of Al 2 Mo 3 O 12 -based materials, providing new insights for the design and preparation of anode materials for low-temperature LIBs.