Structure–Property Relationships in High-Rate Anode Materials Based on Niobium Tungsten Oxide Shear Structures
Structure–Property Relationships in High-Rate Anode Materials Based on Niobium Tungsten Oxide Shear Structures
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DOI：
10.1021/acsaem.2c03573
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发表时间：
2023-01
影响因子：
6.4
通讯作者：
Luke D. Salzer;Brian Diamond;Kelly Nieto;R. C. Evans;A. Prieto;J. Sambur
中科院分区：
文献类型：
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作者：
Luke D. Salzer;Brian Diamond;Kelly Nieto;R. C. Evans;A. Prieto;J. Sambur
nb16w5o55在2018年成为锂离子电池的高倍率负极材料[Griffith et al.,Nature2018,559(7715), 556-563]。这一激动人心的发现点燃了对Wadsley-Roth （W-R）化合物的研究，但系统的实验研究并没有集中在如何调整材料的化学和结构，以达到储能应用所需的性能。在这项工作中，我们系统地研究了一系列氧化铌钨W-R化合物（3 × 4）-Nb12WO33、（4 × 4）-Nb14W3O44和（4 × 5）-Nb16W5O55的结构和组成对容量、锂离子扩散率、充放电曲线和容量损失的影响。恒电位间歇滴定（PITT）数据证实，锂离子扩散系数随块体尺寸的增大而增大，这可归因于锂离子扩散通道数量的增加。小的（3 × 4）- nb12wo33块大小的化合物在四面体上具有优先的W排序，表现出单电子氧化还原，因此，尽管具有最大的理论容量，但测量容量最小。这一观察结果表明，引入阳离子无序（W占据块中心的八面体位点）是评估（3 × 4） Nb12WO33中多电子氧化还原行为的可行策略。不对称嵌段大小的化合物[即（3 × 4）和（4 × 5）嵌段]在第一次循环后表现出最大的容量损失，这可能是由于锂离子在沿剪切面独特的低能袋位捕获所致。最后，充放电曲线的斜率随着块尺寸的增加而增加，这可能是因为能量等效锂离子结合位点的总数也增加了。这种不利的特性使大块无法以固定的c速率提供恒定的功率，比小块更甚。基于这些发现，我们讨论了由W-R材料制成的锂离子插入主机的设计原则。
Nb16W5O55emerged as a high-rate anode material for Li-ion batteries in 2018 [Griffith et al.,Nature2018,559(7715), 556–563]. This exciting discovery ignited research in Wadsley–Roth (W–R) compounds, but systematic experimental studies have not focused on how to tune material chemistry and structure to achieve desirable properties for energy storage applications. In this work, we systematically investigate how structure and composition influences capacity, Li-ion diffusivity, charge–discharge profiles, and capacity loss in a series of niobium tungsten oxide W–R compounds: (3 × 4)-Nb12WO33, (4 × 4)-Nb14W3O44, and (4 × 5)-Nb16W5O55. Potentiostatic intermittent titration (PITT) data confirmed that Li-ion diffusivity increases with block size, which can be attributed to an increasing number of tunnels for Li-ion diffusion. The small (3 × 4)-Nb12WO33block size compound with preferential W ordering on tetrahedral sites exhibits single electron redox and, therefore, the smallest measured capacity despite having the largest theoretical capacity. This observation signals that introducing cation disorder (W occupancy at the octahedral sites in the block center) is a viable strategy to assess multi-electron redox behavior in (3 × 4) Nb12WO33. The asymmetric block size compounds [i.e., (3 × 4) and (4 × 5) blocks] exhibit the greatest capacity loss after the first cycle, possibly due to Li-ion trapping at a unique low energy pocket site along the shear plane. Finally, the slope of the charge–discharge profile increases with increasing block size, likely because the total number of energy-equivalent Li-ion binding sites also increases. This unfavorable characteristic prohibits the large block sizes from delivering constant power at a fixed C-rate more so than the smaller block sizes. Based on these findings, we discuss design principles for Li-ion insertion hosts made from W–R materials.