Xin Cao

Abstract Lithium‐metal batteries (LMBs) with high energy densities are highly desirable for energy storage, but generally suffer from dendrite growth and side reactions in liquid electrolytes; thus the need for solid electrolytes with high mechanical strength, ionic conductivity, and compatible interface arises. Herein, a thiol‐branched solid polymer electrolyte (SPE) is introduced featuring high Li + conductivity (2.26 × 10 −4 S cm −1 at room temperature) and good mechanical strength (9.4 MPa)/toughness (≈500%), thus unblocking the tradeoff between ionic conductivity and mechanical robustness in polymer electrolytes. The SPE (denoted as M‐S‐PEGDA) is fabricated by covalently cross‐linking metal–organic frameworks (MOFs), tetrakis (3‐mercaptopropionic acid) pentaerythritol (PETMP), and poly(ethylene glycol) diacrylate (PEGDA) via multiple CSC bonds. The SPE also exhibits a high electrochemical window (>5.4 V), low interfacial impedance (<550 Ω), and impressive Li + transference number ( t Li+ = 0.44). As a result, Li||Li symmetrical cells with the thiol‐branched SPE displayed a high stability in a >1300 h cycling test. Moreover, a Li|M‐S‐PEGDA|LiFePO 4 full cell demonstrates discharge capacity of 143.7 mAh g −1 and maintains 85.6% after 500 cycles at 0.5 C, displaying one of the most outstanding performances for SPEs to date.

Anionic redox reveals to be a promising strategy to effectively improve the energy density of layered metal oxide cathodes for sodium-ion batteries. However, lattice oxygen loss and derived structural distortion severely hinder its practical application. Herein, combined with anionic and cationic redox activities, we developed a layered structure P2-type Na0.66Li0.22Ti0.15Mn0.63O2 cathode, delivering an initial discharge capacity of 228 mAh g–1 and highly reversible structural evolution as well as improved cyclability. On the basis of comprehensive comparison with Ti-free P2-Na0.66Li0.22Mn0.78O2, both oxygen-related negative behaviors (irreversible O2 evolution and superoxo-related parasitic production) and Mn-related Jahn–Teller distortion have been effectively restrained by simultaneously suppressing both oxygen loss and the participation of Mn4+/Mn3+ redox. Not limited to discovering excess capacity derived from anionic oxidation up charging, our findings not only highlight an effective strategy to stabilize anionic and cationic redox activities but also pave the way for the further improvement of Na-deficient layered materials for high-energy sodium-ion batteries.

Abstract Inspired by hydrophobic interface, a novel design of “polysulfide‐phobic” interface was proposed and developed to restrain shuttle effect in lithium–sulfur batteries. Two‐dimensional VOPO 4 sheets with adequate active sites were employed to immobilize the polysulfides through the formation of a V−S bond. Moreover, owing to the intrinsic Coulomb repulsion between polysulfide anions, the surface anchored with polysulfides can be further evolved into a “polysulfide‐phobic” interface, which was demonstrated by the advanced time/space‐resolved operando Raman evidences. In particular, by introducing the “polysulfide‐phobic” surface design into separator fabrication, the lithium–sulfur battery performed a superior long‐term cycling stability. This work expands a novel strategy to build a “polysulfide‐phobic” surface by “self‐defense” mechanism for suppressing polysulfides shuttle, which provides new insights and opportunities to develop advanced lithium–sulfur batteries.

Abstract Li‐rich oxides can be regarded as the next‐generation cathode materials for high‐energy‐density Li‐ion batteries since additional oxygen redox activities greatly increase output energy density. However, the oxygen loss and structural distortion induce low initial coulombic efficiency and severe decay of cycle performance, further hindering their industrial applications. Herein, the representative layered Li‐rich cathode material, Li 1.2 Ni 0.2 Mn 0.6 O 2 , is endowed with novel single‐crystal morphology. In comparison to its polycrystal counterpart, not only can serious oxygen release be effectively restrained during the first oxygen activation process, but also the layered/spinel phase transition can be well suppressed upon cycling. Moreover, the single‐crystal cathode exhibits the limited volume change and persistent presence of superlattice peaks upon Li + (de)intercalation processes, resulting in enhanced structural stability with absence of crack generation and successive utilization of oxygen redox reaction during long‐term cycling. Benefiting from these unique features, the single‐crystal Li‐rich electrode not only yields a high reversible capacity of 257 mAh g −1 , but also achieves excellent cycling performance with 92% capacity retention after 200 cycles. These findings demonstrate that the morphology design of single crystals can be regarded as an effective strategy to realize high‐energy density and long‐life Li‐ion batteries.

Abstract Triggering oxygen‐related activity is demonstrated as a promising strategy to effectively boost energy density of layered cathodes for sodium‐ion batteries. However, irreversible lattice oxygen loss will induce detrimental structure distortion, resulting in voltage decay and cycle degradation. Herein, a layered structure P2‐type Na 0.66 Li 0.22 Ru 0.78 O 2 cathode is designed, delivering reversible oxygen‐related and Ru‐based redox chemistry simultaneously. Benefiting from the combination of strong Ru 4d‐O 2p covalency and stable Li location within the transition metal layer, reversible anionic/cationic redox chemistry is achieved successfully, which is proved by systematic bulk/surface analysis by in/ex situ spectroscopy (operando Raman and hard X‐ray absorption spectroscopy, etc.). Moreover, the robust structure and reversible phase transition evolution revealed by operando X‐ray diffraction further establish a high degree reversible (de)intercalation processes (≈150 mAh g −1 , reversible capacity) and long‐term cycling (average capacity drop of 0.018%, 500 cycles).