With a high cell-level specific energy and a low cost, lithium-sulfur (Li-S) battery has been intensively studied as one of the most promising candidates for competing the next-generation energy storage campaign. Currently, the practical use of Li-S battery is hindered by the rapidly declined storage performance during battery operation, as caused by irreversible loss of electroactive sulfide species at the cathode, dendrite formation at the anode and parasitic reactions at the electrode-electrolyte interface due to unfavorable cathode-anode crosstalk. In this perspective, we propose to stabilize the Li-S electrochemistry, and improve the storage performance of battery by designing asymmetric electrode-electrolyte interfaces that helps to simultaneously address the differentiated issues at both electrodes and facilitate charge transfer in the electrode/electrolyte and across the interfaces. The strategies that etare discussed would shed lights on reasonable design of battery interfaces towards realization of high-performance Li-S batteries.

The urgent demands for high-energy-density rechargeable batteries promote a flourishing development of Li metal anode. However, the uncontrollable dendrites growth and serious side reactions severely limit its commercial application. Herein, an artificial LiF-rich solid electrolyte interphase (SEI) is constructed at molecular-level using one-step photopolymerization of hexafluorobutyl acrylate based solution, where the LiF is in situ generated during photopolymerization process (denoted as PHALF). The LiF-rich layer comprised flexible polymer matrix and inorganic LiF filler not only ensures intimate contact with Li anode and adapts volume fluctuations during cycling but also regulates Li deposition behavior, enabling it to suppress the dendrite growth and block side reactions between the electrolyte and Li metal. Accordingly, the PHALF-Li anode presents superior stable cycling performance over 500 h at 1 mA·cm^-2 for 1 mA·h·cm^-2 without dendrites growth in carbonate electrolyte. The work provides a novel approach to design and build in situ artificial SEI layer for high-safety and stable Li metal anodes.

The development of new sodium ion battery (SIB) cathodes with satisfactory performance requires an in-depth understanding of their structure-function relationships, to rationally design better electrode materials. In this work, highly ordered, honeycomb-layered Na₃Ni₂SbO₆ was prepared to elucidate the structural evolution and Na⁺ kinetics during electrochemical desodiation/sodiation processes. Structural analysis involving in situ synchrotron X-ray diffraction (XRD) experiments, electrochemical performance measurements, and electrochemical characterization (galvanostatic intermittent titration technique, GITT) methods were used to obtain new insights into the reaction mechanism controlling the (de)intercalation of sodium into the host Na_3-xNi₂SbO₆ structure. Two phase transitions occur (initial O′3 phase → intermediate P′3 phase → final O1 phase) upon Na⁺ extraction; the partial irreversible O′3-P′3 phase transition is responsible for the insufficient cycling stability. The fast Na⁺ mobility (average 10^–12 cm²·s^–1) in the interlayer, high equilibrium voltage (3.27 V), and low voltage polarization (50 mV) establish the linkage between kinetic advantage and a good rate performance of the cathode. These new findings provide deep insight into the reaction mechanism operating in the honeycomb cathode; the present approach could be also extended to investigate other materials for SIBs.

High-capacity Li-rich cathode materials can significantly improve the energy density of lithium-ion batteries, which is the key limitation to miniaturization of electronic devices and further improvement of electrical-vehicle mileage. However, severe voltage decay hinders the further commercialization of these materials. Insights into the relationship between the inherent structural stability and external appearance of the voltage decay in high-energy Li-rich cathode materials are critical to solve this problem. Here, we demonstrate that structural evolution can be significantly inhibited by the intentional introduction of certain adventive cations (such as Ni²⁺) or by premeditated reservation of some of the original Li⁺ ions in the Li slab in the delithiated state. The voltage decay of Li-rich cathode materials over 100 cycles decreased from 500 to 90 or 40 mV upon introducing Ni²⁺ or retaining some Li⁺ ions in the Li slab, respectively. The cations in the Li slab can serve as stabilizers to reduce the repulsion between the two neighboring oxygen layers, leading to improved thermodynamic stability. Meanwhile, the cations also suppress transition metal ion migration into the Li slab, thereby inhibiting structural evolution and mitigating voltage decay. These findings provide insights into the origin of voltage decay in Li-rich cathode materials and set new guidelines for designing these materials for high-energy-density Li-ion batteries.

Owing to the worldwide abundance and low-cost of Na, room-temperature Na-ion batteries are emerging as attractive energy storage systems for large-scale grids. Increasing the Na content in cathode materials is one of the effective ways to achieve high energy density. Prussian blue and its analogues (PBAs) are promising Na-rich cathode materials since they can theoretically store two Na+ ions per formula unit. However, increasing the Na content in PBAs cathode materials remains a major challenge. Here we show that sodium iron hexacyanoferrate with high Na content can be obtained by simply controlling the reducing agent and reaction atmosphere during synthesis. The Na content can reach as high as 1.63 per formula, which is the highest value for sodium iron hexacyanoferrate. This Na-rich sodium iron hexacyanoferrate demonstrates a high specific capacity of 150 mAh·g^-1 and remarkable cycling performance with 90% capacity retention after 200 cycles. Furthermore, the Na intercalation/de-intercalation mechanism has been systematically studied by in situ Raman spectroscopy, X-ray diffraction and X-ray absorption spectroscopy analysis for the first time. The Na-rich sodium iron hexacyanoferrate can function as a plenteous Na reservoir and has great potential as a cathode material for practical Na-ion batteries.

Si has been considered as a promising anode material but its practical application has been severely hindered due to poor cyclability caused by the large volume change during charge/discharge. A new and effective protocol has been developed to construct Si nanoparticle/graphene electrodes with a favorable structure to alleviate this problem. Starting from a stable suspension of Si nanoparticles and graphene oxide in ethanol, spin-coating can be used as a facile method to cast a spin-coated Si nanoparticle/graphene (SC-Si/G) film, in which graphene can act as both an efficient electronic conductor and effective binder with no need for other binders such as polyvinylidenefluoride (PVDF) or polytetrafluoroethylene (PTFE). The prepared SC-Si/G electrode can achieve a high-performance as an anode for lithium-ion batteries benefiting from the following advantages: i) the graphene enhances the electronic conductivity of Si nanoparticles and the void spaces between Si nanoparticles facilitate the lithium ion diffusion, ii) the flexible graphene and the void spaces can effectively cushion the volume expansion of Si nanoparticles. As a result, the binder-free electrode shows a high capacity of 1611 mA·h·g^-1 at 1 A·g^-1 after 200 cycles, a superior rate capability of 648 mA·h·g^-1 at 10 A·g^-1, and an excellent cycle life of 200 cycles with 74% capacity retention.