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Titanate-based compounds have been considered as a hopeful family of anode materials for high-performance lithium-ion batteries due to the “zero-strain” characteristics, low cost, excellent safety and high potential plateau, and free generation of metallic Li and solid electrolyte interphase film. Nonetheless, the large-scale applications of titanate-based compounds are limited by the intrinsically low Li-ion diffusion coefficient and poor electronic conductivity. Considerable efforts have been devoted to solving these challenges towards practical applications, and some crucial progresses have been made. In this review, we present a comprehensive overview of the structural features, transport properties, and modification strategies of titanate-based compounds. The research progress of various effective strategies for enhancing Li-ion diffusion coefficient, electronic conductivity and electrochemical performance are emphatically summarized, including ion-doping, surface modifications, particle morphology control, construction of composite electrodes, etc. This review also gives a compendious summary of gassing mechanism of Li4Ti5O12-based battery and the solution. Designing delicate architectures of carbon coating is an efficient strategy to obtain high-performance titanate-based materials, which can restrain gassing behavior and achieve the high electronic conductivity simultaneously. At last, an insight into the future research directions and further developments of titanate-based compounds is prospected so as to promote their wide application. The review will offer significant comprehension for design and optimization of high performance of the titanate-based compounds.

Achieving long-life is a crucial step for lithium-sulfur (Li-S) batteries as one of most promising next generation energy storage devices. Whereas, the severe shuttling and low redox reaction kinetics of polysulfides (LiPSs) cause the rapid loss of active material, poor rate performance and severe self-discharge. To address above issues, herein, for the first time, we reported the layered LiNi0.8Co0.15Al0.05O2 (NCA) particles as a host to trap LiPSs and accelerate LiPSs conversion simultaneously. We theoretically elucidate and experimentally verify the strong adsorption for Li2S6 through the NCA (104), (003) and (110) crystal planes by the formation of the strong Li-O and Co-S bonds to capture and immobilize LiPSs solidly. At the same time, the intrinsic catalytic effects of NCA with polar surface as an accelerator can propel the LiPSs redox reactions. In addition, NCA can effectively improve static stability of Li-S batteries and suppress their self-discharge behavior. Therefore, the Li-S cells with NCA achieved a high discharge capacity of 755.4 mA h g−1 with a low capacity decay rate of 0.02%/cycle after 500 cycles at 1 C. This work opens up a convenient and effective way to substantially enhance the capability of Li-S batteries for their practical application.

Li7La3Zr2O12 (LLZO) garnet-type oxide has become a promising inorganic electrolyte for solid-state lithium-ion batteries due to its high ionic conductivity and good chemical stability with the lithium metal. However, the poor wettability of LLZO garnet-type oxide with lithium metal and its incompact structure have impeded their extensive applications in solid-state lithium-ion batteries. Herein, Li6.75La3Zr1.75Ta0.25O12 (LLZTO) particles were embedded in the amorphous Li3OCl to form an integrated composite electrolyte (LLZTO-2wt.% Li3OCl) with compact and stable structure at 350 °C, which presents high ionic conductivity (2.27 × 10−4 S cm−1), low interfacial resistance and high electrochemical stability (up to 10 V vs. Li/Li+) at room temperature. The amorphous Li3OCl acting as a binder, filler and bridge promotes the formation of an integrated composite electrolyte and continuous ionic conductive network among LLZTO particles. Furthermore, the Li3OCl with excellent affinity to lithium metal in-situ reacts with the lithium metal to form a stable and dense interfacial layer, which greatly decreases the interfacial resistance between the composite electrolyte and lithium metal (from 1850 to 90 Ω cm2). The interfacial layer allied compact composite electrolyte also effectively suppresses the lithium dendrite growth during lithium plating-striping. The symmetrical Li/LLZTO-2wt.% Li3OCl/Li cell can stably cycle 1000 h without short circuit. The stable specific capacity of solid-state LiFePO4/LLZTO-2wt.% Li3OCl/Li battery is as high as 157.5 mAh g−1 and 85.7 mAh g−1 at 0.05 C and 0.5 C, respectively. Combining the garnet-type electrolyte with amorphous Li3OCl is a promising way to develop the compact garnet-type electrolyte at low temperature for solid-state lithium-ion batteries.

Hollow micro-/nanostructures of metal oxides have attracted tremendous research attention in energy storage due to their unique structural advantages. Although fabrication of spherical hollow architectures have been intensively reported, rational design and facile synthesis of anisotropic hollow structures are still quite challenging, especially for those complex mixed metal oxides with well-controlled interior structures. Herein, through facile citrate-assisted hydrothermal synthesis and subsequent controlled annealing, well-defined octahedral ZnCo2O4 solid, hollow and yolk-shell micro-/nanostructures were constructed for the first time. When used as anode materials for lithium ion batteries (LIBs), the hollow ZnCo2O4 octahedron exhibits the best lithium storage properties, delivering high discharge capacities of 880 mA h g−1 over 160 cycles at 0.2 A g−1, and 650 mA h g−1 over 300 cycles at 1 A g−1. Moreover, it shows a superior high-rate performance with 60% of the specific capacity maintained even at a high current density of 5 A g−1. These features render the hollow octahedral ZnCo2O4 micro-/nanostructure a promising anode for next generation LIBs.

Sliced orange-shaped ZnCo 2 O 4 (SOS-ZCO) constructed by radically aligned subunit nanoparticles is solvothermally synthesized for the first time. When used as lithium-ion battery (LIB) anode, SOS-ZCO demonstrates excellent electrochemical performances benefiting from its advantageous structural features. It shows a high reversible capacity of 890 mA h g −1 at 0.2 A g −1 and good rate capability with capacity retention of 47% at 5 A g −1 . Moreover, it displays a superior cycling stability with 96.5% capacity retention over 130 cycles at 0.2 A g −1 and 92.3% capacity retention over 300 cycles at 1 A g −1 . It is noteworthy that during high-rate cycling, SOS-ZCO anode does not show common pulverization phenomenon to form irregular morphology, but experiences regular morphology transformation. In the first 100 high-rate cycles, SOS-ZCO anode transforms into a network of randomly arranged nanowires with high firmness, leading to negligible capacity fading in the following 200 cycles. Therefore, novel SOS-ZCO micro-/nanostructure exhibits great potential for high-performance LIB anode.

Tin peroxide (SnO2) is one of most potential anode materials for lithium ion batteries with high energy density because of its appropriate (de)lithiation potential and high specific capacity. However, the poor cycling property of SnO2 restricts its wide application in lithium ion battery. Herein, a novel monodispersed porous SnO2 nanospheres/graphene/porous carbon composite electrode with excellent performance is constructed. In this electrode, the SnO2 nanospheres with a diameter of ~60 nm are embedded in porous carbon, which is filled between the interlayers of graphene sheets. The carbon can protect the SnO2 nanospheres from contacting with the electrolyte. The pores inside both SnO2 nanospheres and carbon can accommodate the huge volume expansion of SnO2 nanoparticles during charge–discharge process. The graphene sheets can greatly improve the strength, stability and flexibility of the electrode. The framework formed by graphene and porous carbon can successfully prevent the aggregation of SnO2 nanospheres and collapse of SnO2 composite electrode. As a result, the composite electrode shows excellent rate performance, which achieves discharge capacities of 816.3, 704.6, 600 and 459.4 mAh g−1 at current densities of 0.2, 0.5, 1 and 2 A g−1 and delivers a capacity of 873.2 mAh g−1 after 200 cycles at 0.2 A g−1.

Post-Li-ion high-volumetric electrochemical energy storage devices have been believed as the next generation power sources for portable electronics and electrified vehicles. Sodium-ion capacitors (SICs) are competent for the sake of low cost and high energy-power performance. The most promising positive electrodes for SICs are functionalized carbon electrodes that enable surface-induced redox reactions of sodium cations and exclude the performance degradation caused by sodium insertion/extraction. However, the surface charge storage cannot realize high-volumetric energy storage. In this work, we demonstrate for the first time that folded-graphene electrodes via three-dimensional densification are promising candidates for high-density sodium storage via the surface-induced process. The folded-graphene electrodes delivered the record high volumetric capacity of 132 mA h/cm3 at 0.05 A/g. Even at a 100-times higher current density (5 A/g), the volumetric capacity still preserved 72 mA h/cm3 indicating the great potential for pulse energy output. Moreover, the folded-graphene electrodes demonstrated long-term stability for over 1600 cycles with only 0.01% decay in capacity per cycle. The concept of using 3D folded-graphene electrodes for high volumetric sodium storage can be readily extended to Mg-/Li-ion capacitors and indicates a new avenue towards compact electrochemical energy storage.