Vacant Manganese-Based Perovskite Fluorides@Reduced Graphene Oxides for Na-Ion Storage with Pseudocapacitive Conversion/Insertion Dual Mechanisms.

Na-ion capacitors (NICs) and Na-based dual-ion batteries (Na-DIBs) have been considered to be promising alternatives to traditional lithium-ion batteries (LIBs) because of the abundance and low cost of the Na-ion, but their energy density, power density and life cycle are limited. Herein, dual-vacancy (including K+ and F- vacancies) perovskite fluoride K0.86 MnF2.69 @reduced graphene oxide (rGO; recorded as Mn-G) as anode for NICs and Na-DIBs has been developed. The special conversion/intercalation dual Na-ion energy storage mechanism and pseudocapacitive dynamics are analyzed in detail. The Mn-G//AC NICs and Mn-G//KS6 Na-DIBs delivered a maximum energy density of 92.7 and 187.6 W h kg-1 , a maximum power density of 20.2 and 21.12 kW kg-1 , and long cycle performance of 61.3 and 68.4 % after 1000 cycles at 5 A g-1 , respectively. Moreover, Mn-G//AC NICs and Mn-G//KS6 Na-DIBs can work well over a wide range of temperatures (-20 to 40 °C). These results make it competitive in Na-ion storage applications with high energy/power density over a wide temperature range.

Conversion/Alloying Pseudocapacitance-Dominated Perovskite KZnF3 Anode for Advanced Lithium-Based Dual-Ion Batteries.

Cost-competitive perovskite fluoride KZnF3 has been introduced for the first time as an advanced anode for high-performance lithium-based dual-ion batteries, exhibiting conversion/alloying hybrid mechanisms and dominated pseudocapacitive kinetics for Li-ion storage.

Bimetallic Co-Mn Perovskite Fluorides as Highly-Stable Electrode Materials for Supercapacitors.

Bimetallic Co-Mn perovskite fluorides (KCox Mn1-x F3 , denoted as K-Co-Mn-F) with various Co/Mn ratios (1:0, 12:1, 6:1, 3:1, 1:1, 1:3, 0:1) were prepared through a one-pot solvothermal strategy and further used as electrode materials for supercapacitors. The optimal K-Co-Mn-F candidate (Co/Mn=6:1) showed a size range of 0.1-1 µm and uniform elemental distribution; exhibiting small changes in XRD peaks and XPS binding energy in comparison to the bare K-Co-F and K-Mn-F, due to the structural/electronic effects. Owing to the stronger synergistic effect of Co/Mn redox species, the K-Co-Mn-F (Co/Mn=6:1) electrode exhibited superior specific capacity and rate behavior (113-100 C g-1 at 1-16 Ag-1 ) together with excellent cycling stability (118 % for 5000 cycles at 8 Ag-1 ), and the activated carbon (AC)//K-Co-Mn-F (Co/Mn=6:1) asymmetric capacitor showed superior energy and power densities (8.0-2.4 Wh kg-1 at 0.14-8.7 kW kg-1 ) along with high cycling stability (90 % for 10 000 cycles at 5 Ag-1 ).

Pseudocapacitive trimetallic NiCoMn-111 perovskite fluorides for advanced Li-ion supercabatteries.

Exploring advanced electrochemical energy storage systems and clarifying their charge storage mechanisms are key scientific frontiers presenting a great challenge. Herein, we demonstrate a novel concept of Li-ion supercabatteries (i.e., Li-ion capacitors/batteries, LICBs), which were realized using a novel trimetallic Ni-Co-Mn perovskite fluoride (K0.97Ni0.31Co0.34Mn0.35F2.98, denoted as KNCMF-111 (8#)) anode and a high-performance activated carbon/LiFePO4 (AC/LFP) cathode, which makes the boundary between LICs and LIBs less distinctive. Thanks to the pseudocapacitive conversion mechanism of the KNCMF-111 (8#) anode with superior kinetics and the enhanced capacity of the capacitor/battery hybrid AC/LFP cathode, the designed KNCMF-111 (8#)//AC/LFP LICBs, integrating the synergistic superiority of pseudocapacitive, capacitive and faradaic characteristics, exhibit remarkable energy/power densities and a long cycle life, indicating a high-efficiency energy storage application. Overall, this work provides new insights into exploring advanced Li-ion supercabatteries and clarifying their charge storage mechanisms based on trimetallic Ni-Co-Mn perovskite fluoride electrode materials, which sheds light on the development of advanced electrochemical energy storage systems and in-depth understanding of their charge storage mechanisms.

A F-deficient and high-Mn ternary perovskite fluoride anode with a dominant conversion mechanism for advanced Li-ion batteries.

A F-deficient and high-Mn ternary perovskite fluoride anode (K1.00Ni0.06Co0.14Mn0.80F2.92, KNCMF-3#) has been explored for advanced Li-ion batteries (LIBs), showing a dominant conversion mechanism. Notably, the KNCMF-3#//LiFePO4 (LFP) LIBs furnish an ultra-high performance of 270.5-35.9 W h kg-1/0.63-11.6 kW kg-1/71% retention/5000 cycles/5 A g-1.

A conversion and pseudocapacitance-featuring cost-effective perovskite fluoride KCuF3 for advanced lithium-ion capacitors and lithium-dual-ion batteries.

A cost-effective perovskite fluoride KCuF3 material has been introduced as an advanced anode for lithium-ion capacitors (LICs) and lithium-dual-ion batteries (Li-DIBs), showing a conversion mechanism and pseudocapacitive kinetics for Li ion storage.

Trimetallic NiCoMo/graphene multifunctional electrocatalysts with moderate structural/electronic effects for highly efficient alkaline urea oxidation reaction.

Trimetallic NiCoMo/graphene (NCM/G 811) multifunctional electrocatalysts demonstrate remarkable catalytic activity, fast kinetics, a low onset potential and high stability towards alkaline urea oxidation reaction (UOR). Moderate structural/electronic effects among Ni, Co and Mo species are responsible for the outstanding catalytic behavior.

Engineering doping-vacancy double defects and insights into the conversion mechanisms of an Mn-O-F ultrafine nanowire anode for enhanced Li/Na-ion storage and hybrid capacitors.

The behavior of Li/Na-ion capacitors (LICs/NICs) is largely limited by the low number of electroactive sites in conventional insertion-type anodes. In this work, we demonstrated a novel doping-vacancy double-defective and conversion-type Mn-O-F ultrafine nanowire (denoted as MnF2-E) anode to boost the number of electroactive sites for enhanced LICs/NICs. Owing to the unique hetero oxygen-doping and intrinsic fluorine-vacancy double defects, the Mn-O-F nanowires exhibited superior electroactive sites and thus dramatically enhanced Li/Na-ion storage capability than pristine MnF2 micro/nano-crystals. Both the optimal MnF2 screened by orthogonal experiments and derived Mn-O-F anodes and commercial activated carbon (AC) cathode were used to construct MnF2//AC and MnF2-E//AC LICs/NICs, which were optimized by tuning the active mass ratios of the cathode/anode and the working voltage windows of the hybrid capacitors. The LICs/NICs based on the Mn-O-F anode demonstrated a considerably superior performance than the devices based on the MnF2 anode under the optimal voltages of 0-4 V and 0-4.3 V. The Mn-O-F anode exhibited dominant diffusion/surface-controlled kinetics for Li/Na-ion storage, respectively, showing a major conversion mechanism for the charge storage processes. This work provides a new concept of double-defective and conversion-type electrode materials to improve the Li/Na-ion storage capability and will have a significant impact on the relevant fields.