Boosting the Ultrastable High-Na-Content P2-type Layered Cathode Materials with Zero-Strain Cation Storage via a Lithium Dual-Site Substitution Approach

Abstract

P2-type layered transition-metal (TM) oxides, Na x TMO2, are highly promising as cathode materials for sodium-ion batteries (SIBs) due to their excellent rate capability and affordability. However, P2-type Na x TMO2 is afflicted by issues such as Na+/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 (Na0.80Li0.024­[Li0.065Ni0.22Mn0.66]­O2). 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 (ΔV = 0.7%) in the Na0.80Li0.024­[Li0.065Ni0.22Mn0.66]­O2 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.

Suppressing Voltage Decay in O2-Type Li-Rich Layered Cathode Materials through Microstrain Alleviation

“…The P2-type layered Na 2/3 Ni 0.25 Mn 0.75 O 2 (NNMO-P2) was synthesized via a solid-state reaction in the previous literature. − Typically, the O2-type Li 2/3 □ 1/3 Ni 0.25 Mn 0.75 O 2 was obtained through a Li + /Na + ion exchange process between the Na 2/3 □ 1/3 Ni 0.25 Mn 0.75 O 2 material and LiPF 6 -based carbonate electrolyte at room temperature (LNMO-RT). Subsequently, a heating treatment was applied to Li 2/3 □ 1/3 Ni 0.25 Mn 0.75 O 2 to alleviate strain, resulting in a sample denoted as LNMO-HT.…”

“…The Nyquist plot consists of two semicircles and an inclined straight line . The semicircle at high frequency region is assigned to the interface membrane, known as the interface charge transfer resistance R S . In addition, the semicircle in the intermediate-frequency region is indexed to the charge transfer resistance ( R ct ), ,,, while the inclined straight line in the low-frequency region is associated with the Warburg impedance (W o ). , Figure S6 presents the EIS spectra of two samples, with the inset showing the corresponding equivalent circuit.…”

Ceria Heterostructure Suppresses Oxygen Release of Na-Ion Battery Cathode Materials

“…Recently, manganese-based layered oxides have been reported as a potential cathode candidate for sodium ion batteries because of their high capacity, low cost, and environmental friendliness . Meanwhile, the exploitation of oxygen anionic redox in Na 2/3 TM 1– x Mn x O 2 (TM = Cu, Mg, Zn, Ni, or Li) cathode provided an effective strategy to break through the energy density limitation of the Na-ion batteries. − As an archetypal compound, the Na 2/3 Ni 1/3 Mn 2/3 O 2 (NNM) cathode can achieve an energy density as high as 600 Wh kg –1 through the combination of Ni 2+ /Ni 3+ cationic redox and O 2– /O 2 n– anionic redox. − However, the O 2– /O 2 n– redox is usually accompanied by irreversible oxygen evolution (O 2 n– → O 2 ) from the surface lattice, resulting in undesirable voltage fading and metal dissolution. ,,,− Therefore, stabilizing the surface lattice to suppress oxygen release and metal dissolution is of significant value for the achievement of high energy density SIBs with long cycling stability.…”

Azobenzene-Phenazine-Based D–A Polymer as a Highly Efficient Bipolar Cathode for Sodium-Ion Batteries

“…Today, lithium-ion batteries (LIBs) play an important role in portable electronic devices, new energy vehicles, and large-scale smart grids. , However, there is still an urgent need to find alternatives for LIBs due to the scarcity of lithium resources. Sodium-ion batteries (SIBs) offer a new solution for energy storage due to the abundant reserves of sodium, low price, and the similar working mechanism to LIBs. , The cathode material represents an important constitution in SIBs. − At present, the research on SIB cathode materials mainly focuses on inorganic materials, such as transition metal oxides and polyanionic compounds, however, the large radius of Na + tends to cause the collapse of inorganic materials during the cycling. − …”