Inferior electronic conductivity and sluggish sodium ion diffusion are still two big challenges for TiO₂ anode material for Na ion batteries (SIBs). Herein, we synthesize TiO₂/C composites by the pyrolysis of MIL-125(Ti) precursor and successfully introduce defects to TiO₂/C composite by a simple magnesium reduction. The as-prepared defect-rich TiO_2-δ/C composite shows mooncake-shaped morphology consisting of TiO_2-δ nanocrystals with an average particle size of 5 nm well dispersed in the carbon matrix. When used as a SIBs anode, the defect-rich TiO_2-δ/C composite exhibits a high reversible capacity of 330.2 mAh g⁻¹ at 50 mA g⁻¹ at the voltage range of 0.001–3.0 V and long-term cycling stability with negligible decay after 5000 cycles. Compared with other four TiO₂/C samples, the electrochemical performance of defect-rich TiO_2-δ/C is highly improved, which may benefit from the enhanced electronic/ionic conductivities owing to the defect-rich features, high surface area rendering shortened electronic and ionic diffusion path, and the suppress of the TiO₂ crystal aggregation during sodiation and desodiation process by the carbon matrix.

中文翻译：

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富含缺陷的TiO2-δ纳米晶体被限制在月饼形的多孔碳基质中，作为先进的Na离子电池阳极

对于Na离子电池（SIB）的TiO ₂负极材料，低电子传导性和缓慢的钠离子扩散仍然是两个重大挑战。本文中，我们通过MIL-125（Ti）前体的热解合成了TiO ₂ / C复合材料，并通过简单的镁还原成功地将缺陷引入TiO ₂ / C复合材料。所制备的富含缺陷的TiO2 _-δ / C复合材料显示出月饼状形态，由平均粒径为5 nm的TiO2 _-δ纳米晶体组成，良好地分散在碳基质中。当用作SIBs阳极时，富含缺陷的TiO2 _-δ / C复合材料在50 mA g ^-1时表现出330.2 mAh g ^-1的高可逆容量在0.001–3.0 V的电压范围内，具有5000次循环后的衰减可忽略不计的长期循环稳定性。与其他四个TiO ₂ / C样品相比，富含缺陷的TiO2 _-δ / C的电化学性能得到了极大的改善，这归因于缺陷丰富的特征，高表面积缩短了其得益于增强的电子/离子电导率。电子和离子的扩散路径，以及碳基质抑制在制碱和脱碱过程中TiO ₂晶体的聚集。