Ti C T , a typical representative among the emerging family of 2D layered transition metal carbides and/or nitrides referred to as MXenes, has exhibited multiple advantages including metallic conductivity, a plastic layer structure, small band gaps, and the hydrophilic nature of its functionalized surface. As a result, this 2D material is intensively investigated for application in the energy storage field. The composition, morphology and texture, surface chemistry, and structural configuration of Ti C T directly influence its electrochemical performance, e.g., the use of a well-designed 2D Ti C T as a rechargeable battery anode has significantly enhanced battery performance by providing more chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier/charge-transport kinetics. Some recent progresses of Ti C T MXene are achieved in energy storage. This Review summarizes recent advances in the synthesis and electrochemical energy storage applications of Ti C T MXene including supercapacitors, lithium-ion batteries, sodium-ion batteries, and lithium-sulfur batteries. The current opportunities and future challenges of Ti C T MXene are addressed for energy-storage devices. This Review seeks to provide a rational and in-depth understanding of the relation between the electrochemical performance and the nanostructural/chemical composition of Ti C T , which will promote the further development of 2D MXenes in energy-storage applications.

Ultrathin MoS2/N‐graphene nanosheets with ≈4 nm thickness exhibit exceptional electrochemical performance. Extension of the defect sites and vacancies of the nanosheets results in the increase of capacity during cycling.

improved LIB performance is in the electrode materials. [ 11 ] Presently, commercial anode materials mainly include graphite, which limits the lithium storage performance in terms of energy and power density due to the low theoretical capacity (LiC 6 , 372 mAh g −1 ) and low Li-ion transport rate. [12][13][14] New anode materials with higher capacities are being looked for including mixed transition metal oxide anodes. Traditional Metal Oxide AnodesNew research is constantly being carried out to reach the high requirements for LIB anodes. Various metal oxide materials such as SnO 2 , [15][16][17][18][19] Co 3 O 4 , [20][21][22][23] NiO, [24][25][26][27] Fe 3 O 4 , [28][29][30] and MnO 2 [31][32][33] are alternative potential anodes for LIBs due to their high theoretical capacities, high power density, and wide usefulness. However, metal oxides inevitably suffer from several major problems: severe volume changes during the alloying-dealloying processes, pulverization and agglomeration of primitive particles, and poor electronic conductivity that hinders the reaction with lithium during electrochemical reactions. Numerous approaches have attempted to address these challenges. One useful method is to develop the metal oxide materials into nanostructures. [ 3 ] The distinct lithium storage mechanisms and the infl uence of unique structures on the lithium storage properties of the metal oxide materials have been reported in detail. [ 5 ] A series of work on the design of various nanostructures of metal oxide materials has been subsequently carried out, for nanomaterials of different dimensions, hollow structures, and hierarchical structures. [ 5 ] Coating or combining the buffering matrix or conductive materials with metal oxide materials is another way to relieve the severe problems. [36][37][38][39][40][41][42] Various carbon materials, especially novel nanocarbon materials like carbon nanotubes and graphene nanosheets, have been widely studied as the buffering and conductive agent for metal oxide anodes. [43][44][45][46] In our previous review, [ 47 ] the signifi cant effects of graphene nanosheets on tin-based anodes were summarized in detail. It has been concluded that graphene not only contributes as a highly conductive network, but also as a fl exible supporting layer, effectively relieving the volume change and particle aggregation. In addition, different metals and metal oxides that are electrochemically active and Mixed transition-metal oxides (MTMOs), including stannates, ferrites, cobaltates, and nickelates, have attracted increased attention in the application of high performance lithium-ion batteries. Compared with traditional metal oxides, MTMOs exhibit enormous potential as electrode materials in lithium-ion batteries originating from higher reversible capacity, better structural stability, and high electronic conductivity. Recent advancements in the rational design of novel MTMO micro/nanostructures for lithium-ion battery anodes are summarized and their energy storage mechanism is compared to transit...

As one of the most promising negative electrode materials in lithium‐ion batteries (LIBs), SnO2 experiences intense investigation due to its high specific capacity and energy density, relative to conventional graphite anodes. In this study, for the first time, atomic layer deposition (ALD) is used to deposit SnO2, containing both amorphous and crystalline phases, onto graphene nanosheets (GNS) as anodes for LIBs. The resultant SnO2‐graphene nanocomposites exhibit a sandwich structure, and, when cycled against a lithium counter electrode, demonstrate a promising electrochemical performance. It is demonstrated that the introduction of GNS into the nanocomposites is beneficial for the anodes by increasing their electrical conductivity and releasing strain energy: thus, the nanocomposite electrode materials maintain a high electrical conductivity and flexibility. It is found that the amorphous SnO2‐GNS is more effective than the crystalline SnO2‐GNS in overcoming electrochemical and mechanical degradation; this observation is consistent with the intrinsically isotropic nature of the amorphous SnO2, which can mitigate the large volume changes associated with charge/discharge processes. It is observed that after 150 charge/discharge cycles, 793 mA h g−1 is achieved. Moreover, a higher coulombic efficiency is obtained for the amorphous SnO2‐GNS composite anode. This study provides an approach to fabricate novel anode materials and clarifies the influence of SnO2 phases on the electrochemical performance of LIBs.

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A highly lithium ionic conductive solid-state electrolyte coating layer significantly increases cathode performance in lithium ion batteries.

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Sulfur cathode offers a high theoretical specific capacity of 1,675 mAh g À1 and a high specific energy of 2,600 Wh kg À1 when implemented in lithium-sulfur batteries (LSBs). Moreover, sulfur is the redundant by-product of the petroleum industry, ensuring the low cost of LSBs. These features make LSBs particularly competitive among next-generation energy storage systems. However, the sulfur cathode suffers from several challenges such as a large volume change, low electrical conductivity of sulfur, as well as the polysulfide shuttle effect, which result in low utilization and loss of cathode active materials. Insertion of membranes (or so-called interlayers) between the separator and cathode has been demonstrated as a promising approach to alleviate these issues. In this review, recent progress regarding the advanced interlayer systems are summarized. Specifically, we generalize the different types of interlayers, and the operating mechanisms and widespread availability of interlayers in LSBs are concluded. Furthermore, the scientific/technical challenges and perspective are presented.