RESUMO
Lithium metal is a highly promising anode for next-generation high-energy-density rechargeable batteries. Nevertheless, its practical application faces challenges due to the uncontrolled lithium dendrites growth and infinite volumetric expansion during repetitive cycling. Herein, a composite lithium anode is designed by mechanically rolling and pressing a cerium oxide-coated carbon textile with lithium foil (Li@CeO2/CT). The in situ generated cerium dioxide (CeO2) and cerium trioxide (Ce2O3) form a heterojunction with a reduced lithium-ion migration barrier, facilitating the rapid lithium ions migration. Additionally, both CeO2 and Ce2O3 exhibit higher adsorbed energy with lithium, enabling faster and more distributed interfacial transport of lithium ions. Furthermore, the high specific surface area of 3D skeleton can effectively reduce local current density, and alleviate the lithium volumetric changes upon plating/stripping. Benefiting from this unique structure, the highly compact and uniform lithium deposition is constructed, allowing the Li@CeO2/CT symmetric cells to maintain a stable cycling for over 500 cycles at an exceptional high current density of 100 mA cm-2. When paired with LiNi0.91Co0.06Mn0.03O2 (NCM91) cathode, the cell achieves 74.3% capacity retention after 800 cycles at 1 C, and a remarkable capacity retention of 81.1% after 500 cycles even at a high rate of 4 C.
RESUMO
Microstrain and the associated surface-to-bulk propagation of structural defects are known to be major roadblocks to developing high-energy and long-life batteries. However, the origin and effects of microstrain during the synthesis of battery materials remain largely unknown. Here we perform microstrain screening during real-time and realistic synthesis of sodium layered oxide cathodes. Evidence gathered from multiscale in situ synchrotron X-ray diffraction and microscopy characterization collectively reveals that the spatial distribution of transition metals within individual precursor particles strongly governs the nanoscale phase transformation, local charge heterogeneity and accumulation of microstrain during synthesis. This unexpected dominance of transition metals results in a counterintuitive outward propagation of defect nucleation and growth. These insights direct a more rational synthesis route to reduce the microstrain and crystallographic defects within the bulk lattice, leading to significantly improved structural stability. The present work on microstrain screening represents a critical step towards synthesis-by-design of defect-less battery materials.
RESUMO
Layered iron/manganese-based oxides are a class of promising cathode materials for sustainable batteries due to their high energy densities and earth abundance. However, the stabilization of cationic and anionic redox reactions in these cathodes during cycling at high voltage remain elusive. Here, an electrochemically/thermally stable P2-Na0.67Fe0.3Mn0.5Mg0.1Ti0.1O2 cathode material with zero critical elements is designed for sodium-ion batteries (NIBs) to realize a highly reversible capacity of ≈210 mAh g-1 at 20 mA g-1 and good cycling stability with a capacity retention of 74% after 300 cycles at 200 mA g-1, even when operated with a high charge cut-off voltage of 4.5 V versus sodium metal. Combining a suite of cutting-edge characterizations and computational modeling, it is shown that Mg/Ti co-doping leads to stabilized surface/bulk structure at high voltage and high temperature, and more importantly, enhances cationic/anionic redox reaction reversibility over extended cycles with the suppression of other undesired oxygen activities. This work fundamentally deepens the failure mechanism of Fe/Mn-based layered cathodes and highlights the importance of dopant engineering to achieve high-energy and earth-abundant cathode material for sustainable and long-lasting NIBs.