Bio-based anode material production for lithium-ion batteries through catalytic graphitization of biochar: the deployment of hybrid catalysts.

Producing sustainable anode materials for lithium-ion batteries (LIBs) through catalytic graphitization of renewable biomass has gained significant attention. However, the technology is in its early stages due to the bio-graphite's comparatively low electrochemical performance in LIBs. This study aims to develop a process for producing LIB anode materials using a hybrid catalyst to enhance battery performance, along with readily available market biochar as the raw material. Results indicate that a trimetallic hybrid catalyst (Ni, Fe, and Mn in a 1:1:1 ratio) is superior to single or bimetallic catalysts in converting biochar to bio-graphite. The bio-graphite produced under this catalyst exhibits an 89.28% degree of graphitization and a 73.95% conversion rate. High-resolution transmission electron microscopy (HRTEM) reveals the dissolution-precipitation mechanism involved in catalytic graphitization. Electrochemical performance evaluation showed that the trimetallic hybrid catalyst yielded bio-graphite with better electrochemical performances than those obtained through single or bimetallic hybrid catalysts, including a good reversible capacity of about 293 mAh g-1 at a current density of 20 mA/g and a stable cycle performance with a capacity retention of over 98% after 100 cycles. This study proves the synergistic efficacy of different metals in catalytic graphitization, impacting both graphite crystalline structure and electrochemical performance.

Toward Solid-State 3D-Microbatteries Using Functionalized Polycarbonate-Based Polymer Electrolytes.

3D microbatteries (3D-MBs) impose new demands for the selection, fabrication, and compatibility of the different battery components. Herein, solid polymer electrolytes (SPEs) based on poly(trimethylene carbonate) (PTMC) have been implemented in 3D-MB systems. 3D electrodes of two different architectures, LiFePO4-coated carbon foams and Cu2O-coated Cu nanopillars, have been coated with SPEs and used in Li cells. Functionalized PTMC with hydroxyl end groups was found to enable uniform and well-covering coatings on LiFePO4-coated carbon foams, which was difficult to achieve for nonfunctionalized polymers, but the cell cycling performance was limited. By employing a SPE prepared from a copolymer of TMC and caprolactone (CL), with higher ionic conductivity, Li cells composed of Cu2O-coated Cu nanopillars were constructed and tested both at ambient temperature and 60 °C. The footprint areal capacity of the cells was ca. 0.02 mAh cm-2 for an area gain factor (AF) of 2.5, and 0.2 mAh cm-2 for a relatively dense nanopillar-array (AF = 25) at a current density of 0.008 mA cm-2 under ambient temperature (22 ± 1 °C). These results provide new routes toward the realization of all-solid-state 3D-MBs.

On the P2-NaxCo1-y(Mn2/3Ni1/3)yO2 Cathode Materials for Sodium-Ion Batteries: Synthesis, Electrochemical Performance, and Redox Processes Occurring during the Electrochemical Cycling.

P2-type NaMO2 sodiated layered oxides with mixed transition metals are receiving considerable attention for use as cathodes in sodium-ion batteries. A study on solid solution (1 - y)P2-NaxCoO2-(y)P2-NaxMn2/3Ni1/3O2 (y = 0, 1/3, 1/2, 2/3, 1) reveals that changing the composition of the transition metals affects the resulting structure and the stability of pure P2 phases at various temperatures of calcination. For 0 ≤ y ≤ 1.0, the P2-NaxCo(1-y)Mn2y/3Niy/3O2 solid-solution compounds deliver good electrochemical performance when cycled between 2.0 and 4.2 V versus Na+/Na with improved capacity stability in long-term cycling, especially for electrode materials with lower Co content (y = 1/2 and 2/3), despite lower discharge capacities being observed. The (1/2)P2-NaxCoO2-(1/2)P2-NaxMn2/3Ni1/3O2 composition delivers a discharge capacity of 101.04 mAh g-1 with a capacity loss of only 3% after 100 cycles and a Coulombic efficiency exceeding 99.2%. Cycling this material to a higher cutoff voltage of 4.5 V versus Na+/Na increases the specific discharge capacity to ≈140 mAh g-1 due to the appearance of a well-defined high-voltage plateau, but after only 20 cycles, capacity retention declines to 88% and Coulombic efficiency drops to around 97%. In situ X-ray absorption near-edge structure measurements conducted on composition NaxCo1/2Mn1/3Ni1/6O2 (y = 1/2) in the two potential windows studied help elucidate the operating potential of each transition metal redox couple. It also reveals that at the high-voltage plateau, all of the transition metals are stable, raising the suspicion of possible contribution of oxygen ions in the high-voltage plateau.