Boosting the Ultrastable High-Na-Content P2-type Layered Cathode Materials with Zero-Strain Cation Storage via a Lithium Dual-Site Substitution Approach.
basic_science · Level V
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- Record sourced from PubMed, PMID 37713681.
- Also identified by DOI 10.1021/acsnano.3c07625.
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Abstract
P2-type layered transition-metal (TM) oxides, Na<sub><i>x</i></sub>TMO<sub>2</sub>, are highly promising as cathode materials for sodium-ion batteries (SIBs) due to their excellent rate capability and affordability. However, P2-type Na<sub><i>x</i></sub>TMO<sub>2</sub> is afflicted by issues such as Na<sup>+</sup>/vacancy ordering and multiple phase transitions during Na-extraction/insertion, leading to staircase-like voltage profiles. In this study, we employ a combination of high Na content and Li dual-site substitution strategies to enhance the structural stability of a P2-type layered oxide (Na<sub>0.80</sub>Li<sub>0.024</sub>[Li<sub>0.065</sub>Ni<sub>0.22</sub>Mn<sub>0.66</sub>]O<sub>2</sub>). The experimental results reveal that these approaches facilitate the oxidation of Mn ions to a higher valence state, thereby affecting the local environment of both TM and Na ions. The resulting modification in the local structure significantly improves the Na-ion storage capabilities as required for cathode materials in SIBs. Furthermore, it induces a solid-solution reaction and enables nearly zero-strain operation (Δ<i>V</i> = 0.7%) in the Na<sub>0.80</sub>Li<sub>0.024</sub>[Li<sub>0.065</sub>Ni<sub>0.22</sub>Mn<sub>0.66</sub>]O<sub>2</sub> cathode during cycling. The assembled full cells demonstrate an exceptional rate performance, with a retention rate of 87% at 10 C compared to that of 0.1 C, as well as an ultrastable cycling capability, maintaining a capacity retention of 73% at 2 C after 1000 cycles. These findings offer valuable insights into the electronic and structural chemistry of ultrastable cathode materials with "zero-strain" Na-ion storage.