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To mitigate lithium-polysulfides (Li-PSs) shuttle in lithium-sulfur batteries (LiSBs), a unique carbon-nanotube-encapsulated-sulfur (S@CNT) cathode material with optimum open-ring sizes (ORSs) on the CNT walls were designed using an integrated computational approach followed by experimental validation. By calculating the transport barrier of Li + ion through ORSs on the CNT walls and comparing the molecular size of solvents and Li-PSs with ORSs, optimum open-rings with 16-30 surrounding carbon atoms were predicted to selectively allow transportation of Li + ion and evaporated sulfur while blocking both Li-PS and solvent molecules. A CNT oxidation process was proposed and simulated to generate these ORSs, and the results indicated that the optimum ORSs can be achieved by narrowly controlling the oxidation parameters. Subsequently, S@CNT cathodes were experimentally synthesized, confirming that optimum ORSs were generated in CNT oxidized at 475 K and exhibited more stable cycling behavior.

Li||MoS 2 solid-state batteries have higher volumetric energy density and power density than Li||Li 2 S batteries. However, they suffer from energy and power decay due to the formation of lithium sulfide that has low ionic/electronic conductivity and a strong Li-S bond. Herein, we overcome these challenges by incorporating the catalytic LiI-LiBr compound and carbon black into MoS 2 . The comprehensive simulations, characterizations, and electrochemical evaluations demonstrated that LiI-LiBr significantly reduces Li + /S 2- interaction and increases the ionic conductivity of Li 2 S, thus enhancing the reaction kinetics and Li 2 S/S redox reversibility. MoS 2 @LiI-LiBr@C||Li cells with an areal capacity of 0.87 mAh cm -2 provide a reversible capacity of 816.2 mAh g -1 at 200 mA g -1 and maintain 604.8 mAh g -1 (based on the mass of MoS 2 ) for 100 cycles. At a high areal capacity of 2 mAh cm -2 , the battery still delivers reversible capacity of 498 mAh g -1 . LiI-LiBr-carbon additive can be broadly applied for all transition-metal sulfide cathodes to enhance the cyclic and rate performance.

High-safety, low-cost, and high-volumetric-capacity rechargeable magnesium batteries (RMBs) are promising alternatives to lithium ion batteries. However, lack of high-power, high-energy, and stable cathodes for RMBs hinders their commercialization. Herein, an environmentally benign, low-cost, and sustainable covalent organic framework (COF) cathode for Mg storage is reported for the first time. It delivers a high power density of 2.8 kW kg -1 , a high specific energy density of 146 Wh kg -1 , and an ultralong cycle life of 3000 cycles with a very slow capacity decay rate of 0.0196% per cycle, representing one of the best cathodes to date. The comprehensive electrochemical analysis proves that triazine ring sites in the COF are redox centers for reversible reaction with magnesium ions, and the ultrafast reaction kinetics are mainly attributed to pseudocapacitive behavior. The high-rate Mg storage of the COF offers new opportunities for the development of ultrastable and fast-charge RMBs.

Solid electrolyte interphase (SEI) is crucial for suppressing Li dendrite growth in high-energy lithium metal (LiM) batteries. Unfortunately, the naturally formed SEI on the LiM anode surface in carbonate electrolytes cannot suppress Li dendrites, resulting in a continuous consumption of electrolytes and LiM during cycling. Artificial SEI normally lacks self-healing and self-regulating capability, gradually losing the effectiveness during cycling. In this work, we report the self-regulating phenomenon of LiRAP-ASEI that can effectively suppress Li dendrites and is investigated using in situ optical microscopy and COMSOL multiphysics simulation. The effectiveness of self-regulated LiRAP-ASEI is further evaluated in the most aggressive Li/sulfur cells with a lean electrolyte (10 μL mAh -1 ) and LiRAP-ASEI/LiM (2.5-fold excess of LiM). The LiRAP@Cu∥sulfur@C cells show a stable 3000 cycle life at a current density of 11.5 mA cm -2 . The self-regulated phenomenon holds great promise for the development of high-energy-density LMBs.

Rechargeable Mg batteries, using high capacity and dendrite-free Mg metal anodes, are promising energy storage devices for large scale smart grid due to low cost and high safety. However, the performance of Mg batteries is still plagued by the slow reaction kinetics of their cathode materials. Recent discoveries demonstrate that water in cathode can significantly enhance the Mg-ion diffusion in cathode by an unknown mechanism. Here, we propose the water-activated layered-structure VOPO 4 as a novel cathode material and examine the impact of water in electrode or organic electrolyte on the thermodynamics and kinetics of Mg-ion intercalation/deintercalation in cathodes. Electrochemical measurements verify that water in both VOPO 4 lattice and organic electrolyte can largely activate VOPO 4 cathode. Thermodynamic analysis demonstrates that the water in the electrolyte will equilibrate with the structural water in VOPO 4 lattice, and the water activity in the electrolyte alerts the mechanism and kinetics for electrochemical Mg-ion intercalation in VOPO 4 . Theoretical calculations and experimental results demonstrate that water reduces both the solid-state diffusion barrier in the VOPO 4 electrode and the desolvation penalty at the interface. To achieve fast reaction kinetics, the water activity in the electrolyte should be larger than 10 -2 . The proposed activation mechanism provides guidance for screening and designing novel chemistry for high performance multivalent-ion batteries.

Layered metal oxides have been widely used as the best cathode materials for commercial lithium-ion batteries and are being intensively explored for sodium-ion batteries. However, their application to potassium-ion batteries (PIBs) is hampered because of the poor cycling stability and low rate capability due to the larger ionic size of K + than of Li + or Na + . Herein, a facile self-templated strategy was used to synthesize unique P2-type K 0.6 CoO 2 microspheres that consist of aggregated primary nanoplates as PIB cathodes. The unique K 0.6 CoO 2 microspheres with aggregated structure significantly enhanced the kinetics of the K + intercalation/deintercation and also minimized the parasitic reactions between the electrolyte and K 0.6 CoO 2 . The P2-K 0.6 CoO 2 microspheres demonstrated a high reversible capacity of 82 mAh g -1 at 10 mA g -1 , high rate capability of 65 mAh g -1 at 100 mA g -1 , and long cycle life (87% capacity retention over 300 cycles). The high reversibility of the P2-K 0.6 CoO 2 full cell paired with a hard carbon anode further demonstrated the feasibility of PIBs. This work not only successfully demonstrates exceptional performance of P2-type K 0.6 CoO 2 cathodes and microspheres K 0.6 CoO 2 ∥hard carbon full cells, but also provides new insights into the exploration of other layered metal oxides for PIBs.

Metallic tin has been considered as one of the most promising anode materials both for lithium (LIBs) and sodium ion battery (NIBs) because of a high theoretical capacity and an appropriate low discharge potential. However, Sn anodes suffer from a rapid capacity fading during cycling due to pulverization induced by severe volume changes. Here we innovatively synthesized pipe-wire TiO 2 -Sn@carbon nanofibers (TiO 2 -Sn@CNFs) via electrospinning and atomic layer deposition to suppress pulverization-induced capacity decay. In pipe-wire TiO 2 -Sn@CNFs paper, nano-Sn is uniformly dispersed in carbon nanofibers, which not only act as a buffer material to prevent pulverization, but also serve as a conductive matrix. In addition, TiO 2 pipe as the protection shell outside of Sn@carbon nanofibers can restrain the volume variation to prevent Sn from aggregation and pulverization during cycling, thus increasing the Coulombic efficiency. The pipe-wire TiO 2 -Sn@CNFs show excellent electrochemical performance as anodes for both LIBs and NIBs. It exhibits a high and stable capacity of 643 mA h/g at 200 mA/g after 1100 cycles in LIBs and 413 mA h/g at 100 mA/g after 400 cycles in NIBs. These results would shed light on the practical application of Sn-based materials as a high capacity electrode with good cycling stability for next-generation LIBs and NIBs.

High energy and power densities are the greatest challenge for all-solid-state lithium batteries due to the poor interfacial compatibility between electrodes and electrolytes as well as low lithium ion transfer kinetics in solid materials. Intimate contact at the cathode-solid electrolyte interface and high ionic conductivity of solid electrolyte are crucial to realizing high-performance all-solid-state lithium batteries. Here, we report a general interfacial architecture, i.e., Li 7 P 3 S 11 electrolyte particles anchored on cobalt sulfide nanosheets, by an in situ liquid-phase approach. The anchored Li 7 P 3 S 11 electrolyte particle size is around 10 nm, which is the smallest sulfide electrolyte particles reported to date, leading to an increased contact area and intimate contact interface between electrolyte and active materials. The neat Li 7 P 3 S 11 electrolyte synthesized by the same liquid-phase approach exhibits a very high ionic conductivity of 1.5 × 10 -3 S cm -1 with a particle size of 0.4-1.0 μm. All-solid-state lithium batteries employing cobalt sulfide-Li 7 P 3 S 11 nanocomposites in combination with the neat Li 7 P 3 S 11 electrolyte and Super P as the cathode and lithium metal as the anode exhibit excellent rate capability and cycling stability, showing reversible discharge capacity of 421 mAh g -1 at 1.27 mA cm -2 after 1000 cycles. Moreover, the obtained all-solid-state lithium batteries possesses very high energy and power densities, exhibiting 360 Wh kg -1 and 3823 W kg -1 at current densities of 0.13 and 12.73 mA cm -2 , respectively. This contribution demonstrates a new interfacial design for all-solid-state battery with high performance.

All-solid-state lithium-sulfur batteries (ASSLSBs) using highly conductive sulfide-based solid electrolytes suffer from low sulfur utilization, poor cycle life, and low rate performance due to the huge volume change of the electrode and the poor electronic and ionic conductivities of S and Li2S. The most promising approach to mitigate these challenges lies in the fabrication of a sulfur nanocomposite electrode consisting of a homogeneous distribution of nanosized active material, solid electrolyte, and carbon. Here, we reported a novel bottom-up method to synthesize such a nanocomposite by dissolving Li2S as the active material, polyvinylpyrrolidone (PVP) as the carbon precursor, and Li6PS5Cl as the solid electrolyte in ethanol, followed by a coprecipitation and high-temperature carbonization process. Li2S active material and Li6PS5Cl solid electrolyte with a particle size of ∼4 nm were uniformly confined in a nanoscale carbon matrix. The homogeneous nanocomposite electrode consisting of different nanoparticles with distinct properties of lithium storage capability, mechanical reinforcement, and ionic and electronic conductivities enabled a mechanical robust and mixed conductive (ionic and electronic conductive) sulfur electrode for ASSLSB. A large reversible capacity of 830 mAh/g (71% utilization of Li2S) at 50 mA/g for 60 cycles with a high rate performance was achieved at room temperature even at a high loading of Li2S (∼3.6 mg/cm(2)). This work provides a new strategy to design a mechanically robust, mixed conductive nanocomposite electrode for high-performance all-solid-state lithium sulfur batteries.

In contrast to the stable cycle performance of space confined Se-based cathodes for lithium batteries in carbonate-based electrolytes, their common capacity fading in ether-based electrolytes has been paid less attention and not yet well-addressed so far. In this work, the lithiation/delithiation of amorphous Se2S5 confined in micro/mesoporous carbon (Se2S5/MPC) cathode was investigated by in situ X-ray near edge absorption spectroscopy (XANES) and theoretical calculations. The Se2S5/MPC composite was synthesized by a modified vaporization-condensation method to ensure a good encapsulation of Se2S5 into the pores of MPC host. In situ XANES results illustrated that the lithiation/delithiation reversibility of Se component was gradually decreased in ether-based electrolytes, leading to an aggravated formation of long-chain polyselenides during cycling and further capacity decay. Moreover, ab initio calculations revealed that the binding energy of polyselenides (Li2Sen) with carbon host is in an order of Li2Se6 > Li2Se4 > Li2Se. The insights into the failure mechanism of Se-based cathode gain in this work are expected to serve as a guide for future design on high performance Se-based cathodes.

Conversion-reaction cathodes can potentially double the energy density of current Li-ion batteries. However, the poor cycling stability, low energy efficiency, and low power density of conversion-reaction cathodes limit their applications for Li-ion batteries. Herein, we report a revolutionary advance in a conversion-reaction cathode by developing a core-shell FeOF@PEDOT nanorods, in which partial substitution of fluorine with oxygen in FeF3 substantially enhance the reaction kinetics and reduce the potential hysteresis, while conformal nanolayer PEDOT coating provides a roubst fast electronic connection and prevents the side reactions. The FeOF@PEDOT nanorods deliver a capacity of 560 mA h g(-1) at 10 mA g(-1) with an energy density of >1100 W h kg(-1), which is more than two times higher than the theoretical energy density of LiCoO2. The FeOF@PEDOT nanorods can maintain a capacity of ~430 mA h g(-1) at 50 mA g(-1) (840 W h kg(-1)) for over 150 cycles with capacity decay rate of only 0.04% per cycle, which is 2 orders of magnitude lower than the capacity decay rate ever reported among all conversion-reaction cathodes. Detailed characterizations were conducted to identify the structure and mechanism responsible for these significant improvements that could translate into a Li-ion cell with a 2× increase in energy density.