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A newly designed dense SiO x @carbon nanotubes (CNTs) composite with a high conductivity of 3.5 S cm À1 and tap density of 1.13 g cm À3 was prepared, in which the CNTs were stripped by physical energy crushing and then coated on SiO x nanoparticles. The composite exhibits high capacities of 835 and 687 mAh g À1 at current densities of 100 and 200 mA g À1 , which can be finely persevered over 100 cycles. Benefiting from this promising anode, two new full cells of SiO x @CNTs/LiMn 2 O 4 and SiO x @CNTs/LiNi 0.5 Mn 1.5 O 4 with high energy densities of 2273 and 2747 Wh kg anode À1 (i. e. 413 and 500 Wh kg cathode À1 ), respec-tively, were successfully assembled and can cycle more than 400 cycles. Even with further cycling at the elevated temperature of 45 8C, the cells can still deliver relatively high capacities of 568 and 465 mAh g anode À1 , respectively, over 100 cycles. Such desired high-energy lithium-ion batteries with working voltages over 4.0 V can be widely developed for diverse applications (e. g. in handheld devices, electric vehicles, and hybrid electric vehicles). The easy extension of the presented synthetic strategy and the configuration of high-energy battery system would be significant in materials synthesis and energy-storage devices.[a] Dr.

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A strategy to synthesize a Fe3O4@carbon nanotube (CNT) composite with high tap density of 1.22 g cm−3 and electronic conductivity of 4.1 S cm−1 is developed. The Fe3O4@CNT composite exhibits an extremely high capacity of over 1263 mAh g−1, even after 125 cycles at a current density of 100 mA g−1. Additionally, a lithium‐ion full battery of Fe3O4@CNT|LiNi0.5Mn1.5O4 with an energy density of 2283 Wh kganode−1 (381 Wh kgcathode−1) is successfully configured. After optimization of the work voltage windows and electrolyte additives, it has a capacity retention of 71 % after more than 400 cycles. Using this synthetic strategy, additional metal oxide@CNT (e.g., Co3O4, MnO2, CuO, ZnO) composites with high lithium storage capability are explored, and their electrochemical differences versus the cathode of LiNi0.5Mn1.5O4 are investigated in light of their superior performances. Applying this type of metal oxide‐based composite in full cells is a significant step to the development of high‐energy lithium‐ion batteries and to further applications in current sodium‐ion batteries.