Replacing organic liquid electrolyte with inorganic solid electrolytes (SE) can potentially address the inherent safety problems in conventional rechargeable batteries. However, solid-state batteries (SSBs) have been plagued by the relatively low ionic conductivity of SEs and large charge-transfer resistance between electrode and SE. Here, a new design strategy is reported for improving the ionic conductivity of SE by self-forming a composite material. An optimized Na + ion conducting composite electrolyte derived from the Na 1+n Zr 2 Si n P 3−n O 12 NASICON (Na Super Ionic Conductor) structure is successfully synthesized, yielding ultrahigh ionic conductivity of 3.4 mS cm −1 at 25 °C and 14 mS cm −1 at 80 °C. On the other hand, in order to enhance the charge-transfer rate at the electrode/electrolyte interface, an interface modification strategy is demonstrated by utilization of a small amount of nonflammable and nonvolatile ionic liquid (IL) at the cathode side in SSBs. The IL acts as a wetting agent, enabling a favorable interface kinetic in SSBs. The Na 3 V 2 (PO 4 ) 3 /IL/SE/Na SSB exhibits excellent cycle performance and rate capability. A specific capacity of ≈90 mA h g −1 is maintained after 10 000 cycles without capacity decay under 10 C rate at room temperature. This provides a new perspective to design fast ion conductors and fabricate long life SSBs.

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Silicon is the most promising anode material for the next generation highperformance lithium ion batteries. However, its commercial application is hindered by its poor performance due to the huge volume change during cycling. Although two-dimensional silicon-based materials show significantly improved performance, flexible synthesis of such materials is still a challenge. In this work, silicon-based nanosheets with a multilayer structure are synthesized for the first time by a topochemical reaction. The morphology and oxidation state of these nanosheets can be controlled by appropriate choice of reaction media and oxidants. Benefiting from the hierarchical structure and ultrathin size, when the silicon-based nanosheets are employed as anodes they exhibit a charge (delithiation) capacity of 800 mAh/g after 50 cycles with a maximum coulombic efficiency of 99.4% and good rate performance (647 mAh/g at 1 A/g). This work demonstrates a novel method for preparing nanosheets not only for lithium ion batteries but also having various potential applications in other fields, such as catalysts, electronics and photonics.