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Disordered carbon is the state of the art anode material for Na‐ion batteries due to their increased interlayer spacing and good electronic conductivity. However, its practical application is hindered by average specific capacity, poor rate performance, low coulombic efficiency and limited cycling stability. Herein, we report the superior pseudocapacitance enhanced Na‐ion storage of in situ surface functionalized carbon nanosheets. Anodes composed of ultrathin (~15 nm) carbon nanosheets demonstrated excellent reversible specific capacity (375 mAh/g at 25 mA/g), rate performance (150 mAh/g at 2 A/g), long‐term cycling performance (1000 cycles at 1 A/g) and coulombic efficiency (~100 %). Considerably higher pseudocapacitance (up to ~78 %) is also identified in this case compared to amorphous carbon particles. Spectroscopic and electrochemical studies proved Na‐ion intercalation in to the disordered carbon and pseudocapacitive storage driven by oxygen‐containing surface functional groups. Outstanding electrochemical performance is credited to the synergy between diffusion limited intercalation and pseudocapacitive surface Na‐ion storage. The demonstrated synthetic method of in situ functionalized carbon nanosheets is inexpensive and scalable. The strategy of functional group and morphology induced pseudocapacitive Na‐ion storage offer new prospects to design high‐performance Na‐ion battery electrodes. [ABSTRACT FROM AUTHOR]

Despite the proposed safety, performance, and cost advantages, practical implementation of Mg−Li hybrid batteries is limited due to the unavailability of reliable cathodes compatible with the dual‐ion system. Herein, a high‐performance Mg−Li dual ion battery based upon cobalt‐doped TiO2 cathode was developed. Extremely pseudocapacitance‐type Ti1‐xCoxO2‐y nanosheets consist of an optimum 3.57 % Co‐atoms. This defective cathode delivered exceptional pseudocapacitance (maximum of 93 %), specific capacities (386 mAh g−1 at 25 mA g−1), rate performance (191 mAh g−1 at 1 A g−1), cyclability (3000 cycles at 1 A g−1), and coulombic efficiency (≈100 %) and fast charging (≈11 min). This performance was superior to the TiO2‐based Mg−Li dual‐ion battery cathodes reported earlier. Mechanistic studies revealed dual‐ion intercalation pseudocapacitance with negligible structural changes. Excellent electrochemical performance of the cation‐doped TiO2 cathode was credited to the rapid pseudocapacitance‐type Mg/Li‐ion diffusion through the disorder generated by lattice distortions and oxygen vacancies. Ultrathin nature, large surface area, 2D morphology, and mesoporosity also contributed as secondary factors facilitating superior electrode‐electrolyte interfacial kinetics. The demonstrated method of pseudocapacitance‐type Mg−Li dual‐ion intercalation by introducing lattice distortions/oxygen vacancies through selective doping can be utilized for the development of several other potential electrodes for high‐performance Mg−Li dual‐ion batteries. [ABSTRACT FROM AUTHOR]

An ordered network of interconnected tin oxide (SnO2) nanoparticles with a unique 3D architecture and an excellent lithium-ion (Li-ion) storage performance is derived for the first time through hydrolysis and thermal self-assembly of the solid alkoxide precursor. Mesoporous anodes composed of these ≈9 nm-sized SnO2 particles exhibit substantially higher specific capacities, rate performance, coulombic efficiency, and cycling stabilities compared with disordered nanoparticles and commercial SnO2. A discharge capacity of 778 mAh g-1, which is very close to the theoretical limit of 781 mAh g-1, is achieved at a current density of 0.1 C. Even at high rates of 2 C (1.5 A g-1) and 6 C (4.7 A g-1), these ordered SnO2 nanoparticles retain stable specific capacities of 430 and 300 mAh g-1, respectively, after 100 cycles. Interconnection between individual nanoparticles and structural integrity of the SnO2 electrodes are preserved through numerous charge-discharge process cycles. The significantly better electrochemical performance of ordered SnO2 nanoparticles with a tap density of 1.60 g cm-3 is attributed to the superior electrode/electrolyte contact, Li-ion diffusion, absence of particle agglomeration, and improved strain relaxation (due to tiny space available for the local expansion). This comprehensive study demonstrates the necessity of mesoporosity and interconnection between individual nanoparticles for improving the Li-ion storage electrochemical performance of SnO2 anodes. [ABSTRACT FROM AUTHOR]

A lithium–sulfur (Li–S) battery is one of the post‐lithium‐ion battery chemistry candidates due to the high theoretical capacity of the sulfur cathode (1672 mAh g−1). However, low electronic conductivity of sulfur and severe capacity fading during the charge–discharge process limit the commercial realization of Li–S batteries. The origin of capacity fading is mainly due to the polysulfide shuttling effect, resulting from the dissolution of sulfur in the electrolyte solution. Herein, atomic layer deposition (ALD) (6–8 Å thickness) of alumina is presented as a strategy to suppress capacity degradation on the 2D graphene–sulfur hybrid electrode. Low‐temperature ALD prevents sulfur sublimation from the composite electrode. Despite the insulating property of alumina, atomic layer coating maintains good electrical conductivity, thereby yielding lower charge transfer resistance. Alumina‐coated graphene–sulfur hybrid electrodes (AGS) exhibit a high specific capacity of 960 mAh g−1 at a current density of 50 mA g−1 and retain 519 mAh g−1 after 100 galvanostatic cycles. Superior electrochemical performance is credited to the combination of the high electronic conductivity of multilayered graphene platelets and low charge transfer resistance, resulting from effective polysulfide blocking by the atomic scale Al2O3 coating. [ABSTRACT FROM AUTHOR]