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Sodium Ion Diffusion and Voltage Trends in Phosphates Na4M3(PO4)2P2O7 (M = Fe, Mn, Co, Ni) for Possible High-Rate Cathodes
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2015-07-06 00:00:00 , DOI: 10.1021/acs.jpcc.5b04648 Stephen M. Wood 1 , Chris Eames 1 , Emma Kendrick 2, 3 , M. Saiful Islam 1
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2015-07-06 00:00:00 , DOI: 10.1021/acs.jpcc.5b04648 Stephen M. Wood 1 , Chris Eames 1 , Emma Kendrick 2, 3 , M. Saiful Islam 1
Affiliation
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Polyanionic phosphates have the potential to act as low-cost cathodes and stable framework materials for Na ion batteries. The mixed phosphates Na4M3(PO4)2P2O7 (M = Fe, Mn, Co, Ni) are a fascinating new class of materials recently reported to be attractive Na ion cathodes which display low-volume changes upon cycling, indicative of long-lifetime operation. Key issues surrounding intrinsic defects, Na ion migration mechanisms, and voltage trends have been investigated through a combination of atomistic energy minimization, molecular dynamics (MD), and density functional theory simulations. For all compositions, the most energetically favorable defect is calculated to be the Na/M antisite pair. MD simulations suggest Na+ diffusion extends across a 3D network of migration pathways with an activation barrier of 0.20–0.24 eV, and diffusion coefficients (DNa) of 10–10–10–11 cm2 s–1 at 325 K, suggesting good rate capability. The voltage trends indicate that doping the Fe-based cathode with Ni can significantly increase the voltage, and hence the energy density.
中文翻译：
可能的高速率阴极的磷酸盐Na 4 M 3（PO 4）2 P 2 O 7（M = Fe，Mn，Co，Ni）的钠离子扩散和电压趋势
聚阴离子磷酸盐具有用作Na离子电池的低成本阴极和稳定框架材料的潜力。混合磷酸盐Na 4 M 3（PO 4）2 P 2 O 7（M = Fe，Mn，Co，Ni）是一种引人入胜的新型材料，最近报道是有吸引力的Na离子阴极，其在循环时显示出小体积变化，表明使用寿命长。通过结合原子能最小化，分子动力学（MD）和密度泛函理论模拟，已经研究了围绕固有缺陷，Na离子迁移机制和电压趋势的关键问题。对于所有组合物，计算出在能量上最有利的缺陷是Na / M反位对。MD模拟表明，Na +扩散遍及3D迁移路径网络，其激活势垒为0.20–0.24 eV，扩散系数（D Na）为10 –10 –10 –11 cm在325 K时为2 s –1，表明其良好的速率能力。电压趋势表明，用Ni掺杂铁基阴极可显着提高电压，从而提高能量密度。
更新日期：2015-07-06
中文翻译：
可能的高速率阴极的磷酸盐Na 4 M 3（PO 4）2 P 2 O 7（M = Fe，Mn，Co，Ni）的钠离子扩散和电压趋势
聚阴离子磷酸盐具有用作Na离子电池的低成本阴极和稳定框架材料的潜力。混合磷酸盐Na 4 M 3（PO 4）2 P 2 O 7（M = Fe，Mn，Co，Ni）是一种引人入胜的新型材料，最近报道是有吸引力的Na离子阴极，其在循环时显示出小体积变化，表明使用寿命长。通过结合原子能最小化，分子动力学（MD）和密度泛函理论模拟，已经研究了围绕固有缺陷，Na离子迁移机制和电压趋势的关键问题。对于所有组合物，计算出在能量上最有利的缺陷是Na / M反位对。MD模拟表明，Na +扩散遍及3D迁移路径网络，其激活势垒为0.20–0.24 eV，扩散系数（D Na）为10 –10 –10 –11 cm在325 K时为2 s –1，表明其良好的速率能力。电压趋势表明，用Ni掺杂铁基阴极可显着提高电压，从而提高能量密度。
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