High performance composite of nanosized Li 4 Ti 5 O 12 (LTO)and graphene nanosheets wasfabricated using a novel atomic layer deposition (ALD) seeded process incorporated with hydrothermal lithiation for the first time.TiO 2 nanoislands as seeds were anchored on graphene by ALD process, triggering the unique structure formation of subsequent LTO. The synergistic effects of nanosized LTO and graphene endow the composite with a short lithium ion diffusion path and efficiently conductive network for electron and ion transport, boosting the excellent reversible capacity, rate capability, and cyclic stability as anode materials for lithium ion capacitors (LICs). The reversible capacity of 120.8 mAh g-1 at an extremely high current rate of 100 C was achievedsuccessfully, and the electrode can be charged/discharged to about 70% of the theoretical capacity of LTO in 25 s. Meanwhile, the composite exhibited excellent cyclic stability of 90% capacity retention at 20 C with nearly 100% Coulombic efficiency after 2500 cycles. The sintering treatment after hydrothermal reaction has significant effects on the crystallinity, defect density, microstructureandelectrochemical property of the composite, which is also supported by theoreticalcalculations. The results provide a versatile roadmap for synthesis of high performance LTO based composite and new insights into LICs.

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Given natural abundance of Na and superior kinetics of Se, Na–Se batteries have attracted much attention but still face the problem of shuttling effect of soluble intermediates. The first‐principle calculations reveal the S‐decorated Ti3C2 exhibits increased binding energy to sodium polyselenides, suggesting a better capture and restriction on intermediates. The obtained Se@S‐decorated porous Ti3C2 (Se@S‐P‐Ti3C2) exhibits a high reversible capacity of 765 mAh g−1 at 0.1 A g−1 (calculated based on Se), ≈1.2, 1.3, and 1.7 times of Se@porous Ti3C2 (Se@P‐Ti3C2), Se@Ti3C2, and Se, respectively. It gives considerable capacity of 664 mAh g−1 at 20 A g−1 and impressive cycling stability over 2300 cycles with an ultralow capacity decay of 0.003% per cycle. The excellent electrochemical performance can be ascribed to the S‐modified porous Ti3C2, which provides effective immobilization toward polyselenides, makes full use of nanosized Se, and alleviates volume expansion during sodiation/desodiation. Additionally, in situ forming Cu2Se can generate Cu nanoparticles through discharge process and then transform polyselenides into solid‐phase Cu2Se, further suppressing the shuttling effect. This work provides a practical strategy to immobilize and transform sodium polyselenides for high‐capacity and long‐life Na–Se batteries.

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