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Li-excess Mn-based cathodes are thought to be viable cathode materials for next-generation lithium-ion batteries by reason of high discharge capacity and cheap price. However, the initial lattice oxygen loss and structural degradation lead to serious voltage decay and capacity fading in cycling, which significantly restricts their practical usage. Herein, VPO5 is coated on spherical Li1.2Ni0.13Co0.13Mn0.54O2 (LNCMO) by a simple wet chemical method. The VPO5 layer shows good effect in inhibiting the initial irreversible O2 release, increasing the structural stability of LNCMO, and suppressing side reactions at the interface of electrolyte and electrode. It turns out that the 2 wt% VPO5-coated LNCMO possesses a discharge capacity of 289.8 mAh g−1 at 0.1C with improved coulombic efficiency from 70.3 to 85.8%. The capacity retention is 80.8% after 200 cycles at 1C with average discharge voltage declines from 3.97 to 2.95 mV per cycle. This work shows that VPO5 surface layer can effectively improve the cycling performances of LNCMO and provides an idea to modify Li-excess Mn-based cathode materials. [ABSTRACT FROM AUTHOR]

Hard carbon (HC) has become the most promising anode material for sodium‐ion batteries (SIBs), but its plateau capacity at ≈0.1 V (Na+/Na) is still much lower than that of graphite (372 mAh g−1) in lithium‐ion batteries (LIBs). Herein, a CO2‐etching strategy is applied to generate abundant closed pores in starch‐derived hard carbon that effectively enhances Na+ plateau storage. During CO2 etching, open pores are first formed on the carbon matrix, which are in situ reorganized to closed pores through high‐temperature carbonization. This CO2‐assisted pore‐regulation strategy increases the diameter and the capacity of closed pores in HC, and simultaneously maintains the microsphere morphology (10–30 µm in diameter). The optimal HC anode exhibits a Na‐storage capacity of 487.6 mAh g−1 with a high initial Coulomb efficiency of 90.56%. A record‐high plateau capacity of 351 mAh g−1 is achieved, owing to the abundant closed micropores generated by CO2‐etching. Comprehensive in situ and ex situ tests unravel that the high Na+ storage performance originates from the pore‐filling mechanism in the closed micropores. [ABSTRACT FROM AUTHOR]

Lithium‐ion capacitor (LIC) is a promising energy storage device, which combines double advantages of high‐energy lithium‐ion batteries (LIBs) and high‐power supercapacitors. However, the reported anode materials for LICs are synthesized based on the high‐purity chemicals under complicated and time‐consuming conditions, which exhibit a prohibitive cost in practical application. Herein, natural molybdenite is employed as the precursor to construct a high‐capacity and low‐cost anode material of LICs. Specifically, molybdenite is exfoliated into thin‐layer MoS2 under the interaction of hydrazine hydrate and sodium hydroxide, and then coupled with reduced graphene oxide to form a MoS2@rGO composite. Resulting from high reactive activity and structural stability, the MoS2@rGO anode shows excellent lithium‐ion storage performance including high specific capacity (936 mAh g−1 at 100 mA g−1) and rate capability (446 mAh g−1 at 5000 mA g−1). By using MoS2@rGO as an anode and activated carbon as a cathode, the assembled LIC device provides a maximum energy density of 105 Wh kg−1. Even at a high power density of 25 000 W kg−1, the energy density is still up to 65 Wh kg−1. This work provides a reference for the commercial utilization of natural molybdenum resources in the energy storage field. [ABSTRACT FROM AUTHOR]

Sodium-ion capacitors (SICs) have been designed to combine the advantages of high-energy batteries and high-power capacitors as well as low-cost sodium resources. However, anode materials usually exhibit sluggish diffusion of Na+, which results in kinetics imbalance with the capacitive cathode. Herein, the zeolitic imidazolate framework-8 (ZIF-8) layer is uniformly grown on the graphite surface (ZIF-8@Gr) to promote solvated-Na+ co-intercalation reactions in an ether electrolyte. The ZIF-8 coating can act as a multifunctional protection layer to inhibit electrolyte decomposition in the initial cycle, and also withstand volume expansion of graphite during the long-term co-intercalation process. The initial coulombic efficiency (ICE) of the ZIF-8@Gr electrode can be improved to 86%, much higher than that of the pristine graphite electrode (58%). More importantly, the ZIF-8@Gr electrode possesses ultrafast-charging sodium storage (20 A g−1, a full charge time within 16.2 s) and ultralong cycle life (96% and 94% capacity retention after 15 000 and 20 000 cycles at 5 A g−1 and 10 A g−1, respectively). By coupling the ZIF-8@Gr electrode with the activated carbon (AC) as the positive electrode, the as-fabricated SIC device demonstrates impressive energy//power densities (82 W h kg−1 at 518 W kg−1, 47 W h kg−1 at 10 370 W kg−1). These results indicate that ZIF-based surface modification enables graphite as a fast-charging and long-term cycling sodium-storage material. [ABSTRACT FROM AUTHOR]