Na+/Vacancy Disordered P2-Na0.67Co1–xTixO2: High-Energy and High-Power Cathode Materials for Sodium Ion Batteries,ACS Applied Materials & Interfaces

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Na+/Vacancy Disordered P2-Na0.67Co1–xTixO2: High-Energy and High-Power Cathode Materials for Sodium Ion Batteries
ACS Applied Materials & Interfaces ( IF 8.3 ) Pub Date : 2018-01-19 00:00:00 , DOI: 10.1021/acsami.7b16077
Seok Mun Kang _{1,

2} , Jae-Hyuk Park _{1,

2} , Aihua Jin _{1,

2} , Young Hwa Jung ₃ , Junyoung Mun ₄ , Yung-Eun Sung _{1,

2}

Affiliation

Although sodium ion batteries (NIBs) have gained wide interest, their poor energy density poses a serious challenge for their practical applications. Therefore, high-energy-density cathode materials are required for NIBs to enable the utilization of a large amount of reversible Na ions. This study presents a P2-type Na_0.67Co_1–xTi_xO₂ (x < 0.2) cathode with an extended potential range higher than 4.4 V to present a high specific capacity of 166 mAh g^–1. A group of P2-type cathodes containing various amounts of Ti is prepared using a facile synthetic method. These cathodes show different behaviors of the Na⁺/vacancy ordering. Na_0.67CoO₂ suffers severe capacity loss at high voltages due to irreversible structure changes causing serious polarization, while the Ti-substituted cathodes have long credible cycleability as well as high energy. In particular, Na_0.67Co_0.90Ti_0.10O₂ exhibits excellent capacity retention (115 mAh g^–1) even after 100 cycles, whereas Na_0.67CoO₂ exhibits negligible capacity retention (<10 mAh g^–1) at 4.5 V cutoff conditions. Na_0.67Co_0.90Ti_0.10O₂ also exhibits outstanding rate capabilities of 108 mAh g^–1 at a current density of 1000 mA g^–1 (7.4 C). Increased sodium diffusion kinetics from mitigated Na⁺/vacancy ordering, which allows high Na⁺ utilization, are investigated to find in detail the mechanism of the improvement by combining systematic analyses comprising TEM, in situ XRD, and electrochemical methods.

中文翻译：

Na ⁺ /空位无序P2-Na _0.67 Co _{1– x} Ti _x O ₂：用于钠离子电池的高能和高功率阴极材料

尽管钠离子电池（NIB）引起了广泛的兴趣，但其差的能量密度对其实际应用提出了严峻的挑战。因此，NIB需要高能量密度的阴极材料，以能够利用大量可逆的Na离子。这项研究提出了一种P2型Na _0.67 Co _{1– x} Ti _x O ₂（x <0.2）阴极，其扩展电位范围高于4.4 V，具有166 mAh g ^–1的高比容量。使用简便的合成方法制备一组含各种量Ti的P2型阴极。这些阴极显示出Na ⁺ /空位有序的不同行为。钠_0.67由于不可逆的结构变化导致严重的极化，CoO ₂在高电压下会遭受严重的容量损失，而Ti取代的阴极具有长期可靠的循环能力以及高能量。特别是，即使经过100次循环，Na _0.67 Co _0.90 Ti _0.10 O _2仍具有出色的容量保持能力（115 mAh g ^–1），而Na _0.67 CoO ₂在4.5 V截止条件下仍具有可忽略的容量保持力（<10 mAh g ^–1）。Na _0.67 Co _0.90 Ti _0.10 O ₂还具有出色的108 mAh g倍率能力^–1在1000 mA g ^-¹的电流密度下（7.4 C）。研究了减少的Na ⁺ /空位排序增加的钠扩散动力学，从而提高了Na ^+的利用率，通过结合包括TEM，原位XRD和电化学方法在内的系统分析，详细研究了改善机理。

更新日期：2018-01-19

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