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Interlocking biphasic chemistry for high-voltage P2/O3 sodium layered oxide cathode
Energy Storage Materials ( IF 20.4 ) Pub Date : 2022-06-12 , DOI: 10.1016/j.ensm.2022.06.012
Lianzheng Yu, Zhiwei Cheng, Kang Xu, Yu-Xin Chang, Yi-Hu Feng, Duo Si, Mengting Liu, Peng-Fei Wang, Sailong Xu

Biphasic hybridization of layered cathode materials for sodium-ion batteries (SIBs) is crucial to enhance storage performances. The synergistic effect of biphases is generally considered to underlie the enhancement, yet the in-depth mechanism underneath remains unclear, in particular at high-voltages (> 4.2 V, vs Na+/Na). Herein, a unique high-voltage-stable P2/O3 composite layered oxide-Na0.85Ni0.34Mn0.33Ti0.33O2 with a specific proportion (P2:O3 = 24.8%:75.2%) is reported via tuning the amounts of Ti substitution in Na0.85Ni0.34Mn0.66-xTixO2. Operando X-ray diffraction reveals that the biphasic Na0.85Ni0.34Mn0.33Ti0.33O2 cathode successfully restrains the formation of O2 phase and undergoes completely reversible structural evolution of P2/O3–P2/P3–OP4/OP2 upon being charged to a high voltage of 4.4 V. Moreover, the interlocking effect between the phase boundaries is revealed to effectively mitigate the severe structural strain and large lattice volume change, thus further raising its structural stability under the high-voltage regions. Consequently, the obtained biphasic P2/O3-Na0.85Ni0.34Mn0.33Ti0.33O2 cathode exhibits an excellent capacity retention of 80.6% at 1C after 200 cycles. More importantly, the full cell fabricated with hard carbon anode achieves a high energy density of 294.6 Wh kg−1. These results highlight the excellent electrochemical performance of biphasic cathode materials and also grasp new insight into designing composite structure materials for SIBs.



中文翻译:

用于高压 P2/O3 钠层状氧化物正极的联锁双相化学

用于钠离子电池(SIB)的层状正极材料的双相杂化对于提高存储性能至关重要。双相的协同效应通常被认为是增强的基础,但其深层机制仍不清楚,特别是在高电压下(> 4.2 V,vs Na + /Na)。在此,通过调整Ti取代量,报道了具有特定比例(P2:O3 = 24.8%:75.2%)的独特的高压稳定P2/O3复合层状氧化物-Na 0.85 Ni 0.34 Mn 0.33 Ti 0.33 O 2在 Na 0.85 Ni 0.34 Mn 0.66-x Ti x O 2中。Operando X 射线衍射表明,双相 Na 0.85 Ni 0.34 Mn 0.33 Ti 0.33 O 2正极成功抑制了 O2 相的形成,并在充电至4.4 V的高压。此外,相界之间的互锁效应被揭示,有效地缓解了严重的结构应变和大的晶格体积变化,从而进一步提高了高压区域下的结构稳定性。因此,得到的双相P2/O3-Na 0.85 Ni 0.34 Mn 0.33 Ti 0.33 O 2正极在 1C 循环 200 次后表现出 80.6% 的出色容量保持率。更重要的是,用硬碳阳极制造的全电池实现了294.6 Wh kg -1的高能量密度。这些结果突出了双相正极材料优异的电化学性能,并为设计用于 SIB 的复合结构材料提供了新的见解。

更新日期:2022-06-12
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