Magnesium battery is a recently emerging energy storage system that has attracted considerable attention. However, its development is limited by the lack of proper electrode materials for reversible Mg²⁺ intercalation/de-intercalation with satisfied capacity. Here, we firstly report easy synthesis of Ti-deficient bronze titanium dioxide nanowires by topology transformation of H-titanate precursor. It’s found OH⁻ anions substitution of O²⁻ supports the formation of Ti vacancies in TiO₂(B) with a high concentration, denoted as (Ti_0.91O_1.64(OH)_0.36), and can be utilized as a robust host for Mg-ion storage. Both the theoretical and experimental study revealed that Ti-deficient TiO₂(B) exhibits much improved electronic properties with unpaired electrons. Density functional theory (DFT) calculations also reveal Ti vacancies provide more feasible binding sites for Mg-ion. More importantly, it’s surprisingly found the presence of protons enables a suitable binding energy for Mg-ion intercalation and extraction. As a result, such material displays discharge and charge capacities of 217.3 and 165.3 mA h g^-1 at 0.02 A g^-1, representing the highest value among the reported Ti-based electrode materials as well as a high initial Columbic efficiency up to 76.1%. This study gives a new and in-depth view on how cation-deficient structure regulates and promotes the reversible energy storage.

镁电池是一种新兴的储能系统，已经引起了广泛的关注。然而，由于缺乏合适的电极材料用于容量可满足的可逆Mg ²⁺嵌入/脱嵌，其发展受到了限制。在这里，我们首先报道通过H-钛酸酯前体的拓扑转化，容易合成Ti不足的青铜二氧化钛纳米线。它的发现OH ^-的O-取代阴离子^2-支持TI空位以TiO形成₂有高浓度（B），表示为（钛_0.91 ø _1.64（OH）_0.36），并且可以用作Mg离子存储的可靠主机。理论和实验研究均表明，缺乏Ti的TiO ₂（B）在电子不成对的情况下具有改善的电子性能。密度泛函理论（DFT）的计算还表明，Ti空位为Mg离子提供了更可行的结合位点。更重要的是，令人惊讶地发现质子的存在为Mg离子的嵌入和萃取提供了合适的结合能。结果，这种材料在0.02 A g ^-1时显示出217.3和165.3 mA hg ^-1的放电和充电容量代表了已报道的钛基电极材料中的最高值，以及高达76.1％的高初始哥伦布效率。这项研究为阳离子不足的结构如何调节和促进可逆储能提供了新的深入的见解。