To improve the structure stability and accelerate electrochemical reaction kinetics, oxygen vacancies-enriched sub-7 nm Bi_2.88Fe₅O_12-x nanoparticles with high electrochemical activity have been elaborately anchored on two-dimensional MXene nanosheets through a facile electrostatic assembly approach for electrochemical energy storage. MXene nanosheets could not only effectively buffer the serious volume change of Bi_2.88Fe₅O_12-x nanoparticles but also facilitate fast electron transfer as a flexible, well-conductive but robust substrate in the fast charge/discharge processes. Owing to the three-dimensional distinct structure and the strong synergistic effects between MXene and Bi_2.88Fe₅O_12-x nanoparticles, the obtained composite exhibits impressive electrochemical performances. The composite electrode possesses high gravimetric specific capacity of 176 mAh g⁻¹ with ultrahigh volumetric specific capacity of 476 mAh cm⁻³ at 0.5 A g⁻¹ in an aqueous electrolyte, superior to those of the so-far reported Bi₂O₃-based electrode materials. In addition, our fabricated asymmetric device displays a high volumetric energy density of 177 Wh L⁻¹ and remarkable cycling performance with 93.3% retention ratio after 10,000 cycles. Moreover, the resultant MXene/Bi_2.88Fe₅O_12-x composite presents high reversible specific capacity of 805 mAh g⁻¹ for Li-ion storage, corresponding to the volumetric specific capacity of 2176 mAh cm^−‍3.

为了提高结构稳定性并加快电化学反应动力学，已通过一种简便的静电组装方法将具有高电化学活性的富氧空缺的亚7 nm Bi _2.88 Fe ₅ O _{12- x}纳米颗粒精心固定在二维MXene纳米片上。能源储备。MXene纳米片不仅可以有效地缓冲Bi _2.88 Fe ₅ O _{12- x}的严重体积变化纳米粒子，但在快速充电/放电过程中，作为柔性，导电性好但坚固的基材，也有助于快速电子转移。由于MXene与Bi _2.88 Fe ₅ O _{12- x}纳米粒子之间的三维独特结构和强协同作用，所得复合材料表现出令人印象深刻的电化学性能。该复合电极在水性电解质中在0.5 A g ^-1下具有176 mAh g ^-1的高比重比容量和476 mAh cm ^-3的超高体积比容量，优于迄今报道的Bi ₂ O ₃基电极材料。此外，我们制造的非对称器件在10,000次循环后显示出177 Wh L ^-1的高体积能量密度和出色的循环性能，保留率为93.3％。此外，所得的MXene / Bi _2.88 Fe ₅ O _{12- x}复合材料具有用于锂离子存储的805 mAh g ^-1的高可逆比容量，对应于2176 mAh cm ^-3的体积比容量。