Boosting the Electrochemical Performance of Primary and Secondary Lithium Batteries with Mn-Doped All-Fluoride Cathodes.

Transition metal fluorides are potentially high specific energy cathode materials of next-generation lithium batteries, and strategies to address their low conductivity typically involve a large amount of carbon coating, which reduces the specific energy of the electrode. In this study, MnyFe1-yF3@CFx was generated by the all-fluoride strategy, converting most of the carbon in MnyFe1-yF3@C into electrochemical active CFx through a controllable NF3 gas phase fluorination method, while still retaining a tightly bound graphite layer to provide initial conductivity, which greatly improved the energy density of the composite. This synergistic effect of nonfluorinated residual carbon (∼11%) and Mn doping ensures the electrochemical kinetics of the composite. The loading mass of the active substance had been increased to 86%. The theoretical and actual discharge capacity of MnyFe1-yF3@CFx composite was up to 765 mAh g-1 (pure FeF3 is 712 mAh g-1) and 728 mAh g-1, respectively. The discharge capacity at the high-voltage (3.0 V) platform was more than three times higher than that of the non-Mn-doped composite (FeF3@CFx).

Solvation Structure Tuning Induces LiF/Li3 N-Rich CEI and SEI Interfaces for Superior Li/CFx Batteries.

The electrode/electrolyte interfaces play an important role in the electrochemical reaction kinetics to alleviate the severe polarization and voltage hysteresis in lithium primary batteries. Herein, C5 F5 N is proposed as an electrolyte additive to tune the characteristics of the electrode/electrolyte interfaces. The Li/CFx primary battery with C5 F5 N additive exhibits an excellent discharge-specific capacity of 981.4 mAh g-1 (0.1 C), a remarkable high-rate capability of 598 mAh g-1 (15 C), and an outstanding energy/power density of 1068.7 Wh kg-1 /24362.5 W kg-1 . It also shows remarkable storage performance with 717.2 mAh g-1 at 0.1 C after storage at 55 °C for 2 months. The excellent performance of the Li/CFx batteries is closely related to the improved and stable Li3 N/LiF-rich homogeneous interfaces induced by the C5 F5 N additive, which results in uniform distribution of Li+ flux, facilitated electrochemical kinetics, and increased rate capability of Li/CFx battery. Therefore, C5 F5 N is expected to be a promising electrolyte additive, and the related electrode/electrolyte interface engineering provides an effective and facile strategy to increase the performance of the lithium primary battery.

Nanostructured Iron Fluoride Derived from Fe-Based Metal-Organic Framework for Lithium Ion Battery Cathodes.

A comprehensive strategy for the morphological control of octahedral and spindle Fe-based metal-organic frameworks (Fe-MOFs) via microwave-assisted adjustment is proposed in this research. Afterward, in situ copyrolysis under N2 atmosphere contributes to the fabrication of two shape-maintained FeF3·0.33H2O nanostructures (named O-FeF3·0.33H2O and S-FeF3·0.33H2O, respectively) with confined hierarchical porosity and graphitized carbon skeleton. The lithium storage performances for the MOF-derived octahedral O-FeF3·0.33H2O and spindle S-FeF3·0.33H2O composites are investigated, and the prospective lithium storage mechanism is discussed. As a result, the main product of the porous O-FeF3·0.33H2O structure is found to be a promising cathode material for lithium ion batteries owing to its advantageous electrochemical capability. Even after being cycled over 1000 times at 2 C (1 C = 237 mAh g-1), the capacity attenuation rate of the as-prepared O-FeF3·0.33H2O electrode is as low as 0.039% per cycle. The combination of proper octahedral morphology and highly graphitized carbon modification can not only enhance the conductivity of the cathode but also promote the diffusion of Li+ effectively. The remarkable performance of octahedral O-FeF3·0.33H2O can be confirmed by the Li-ion diffusion coefficient (DLi+) calculation analysis and kinetics analysis of lithium storage behavior.

Copper nanowires and copper foam multifunctional bridges in zeolitic imidazolate framework-derived anode material for superior lithium storage.

Herein, a synthetic strategy for growing trimetallic zeolitic imidazolate framework (ZIF) polyhedrons on copper foam (CF) and interweaving with copper nanowires (CNWs) is proposed. Subsequently, in situ annealing under N2 atmosphere leads to the formation of multi-doped CNWs/Cu0.39Zn0.14Co2.47O4-ZnO/CF (CNWs/CZCOZ/CF). The unique structural characteristics of CNWs/CZCOZ/CF allow it to be directly assembled as a working electrode, without additional conductive additives or binders. When it's used as the lithium-ion battery (LIB) anode, this electrode exhibits a significantly high capacity of 2305 mAh g-1 at 0.1 A g-1 after 500 cycles. More importantly, kinetic analysis on the basis of cyclic voltammograms (CVs) indicates that the pseudocapacitive effect is the primary contributor to the high lithium storage capacity and also accounts for the exceptionally high rate capacity of 713 mAh g-1 even if the current density is at a maximum of 10 A g-1. Moreover, the superior battery performance originates from their advantageous structural diversity and unique compositional features, including synergistic effects among polymetallic components and two highly conductive substrates (CNWs and CF), forming unhindered paths for fast charge transfer.