4.0 V aqueous LIBs of both high energy density and high safety are made possible by a new interphase formed from an ''inhomogeneous additive'' approach that effectively stabilizes graphite or lithium-metal anode materials.

In carbonate electrolytes, the organic–inorganic solid electrolyte interphase (SEI) formed on the Li‐metal anode surface is strongly bonded to Li and experiences the same volume change as Li, thus it undergoes continuous cracking/reformation during plating/stripping cycles. Here, an inorganic‐rich SEI is designed on a Li‐metal surface to reduce its bonding energy with Li metal by dissolving 4m concentrated LiNO3 in dimethyl sulfoxide (DMSO) as an additive for a fluoroethylene‐carbonate (FEC)‐based electrolyte. Due to the aggregate structure of NO3− ions and their participation in the primary Li+ solvation sheath, abundant Li2O, Li3N, and LiNxOy grains are formed in the resulting SEI, in addition to the uniform LiF distribution from the reduction of PF6− ions. The weak bonding of the SEI (high interface energy) to Li can effectively promote Li diffusion along the SEI/Li interface and prevent Li dendrite penetration into the SEI. As a result, our designed carbonate electrolyte enables a Li anode to achieve a high Li plating/stripping Coulombic efficiency of 99.55 % (1 mA cm−2, 1.0 mAh cm−2) and the electrolyte also enables a Li||LiNi0.8Co0.1Mn0.1O2 (NMC811) full cell (2.5 mAh cm−2) to retain 75 % of its initial capacity after 200 cycles with an outstanding CE of 99.83 %.

Hybrid aqueous/non-aqueous electrolyte (HANE) inherits the merits from both aqueous (non-flammability) and non-aqueous (high electrochemical stability) systems. Its unique assembly at the inner-Helmholtz interface leads to an interphasial chemistry that supports a 3.2 V Li 4 Ti 5 O 12 /LiNi 0.5 Mn 1.5 O 4 full aqueous Li-ion battery with performances comparable with state-of-the-art Li-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 KCoO microspheres that consist of aggregated primary nanoplates as PIB cathodes. The unique KCoO microspheres with aggregated structure significantly enhanced the kinetics of the K intercalation/deintercation and also minimized the parasitic reactions between the electrolyte and KCoO. The P2-KCoO microspheres demonstrated a high reversible capacity of 82 mAh g at 10 mA g, high rate capability of 65 mAh g at 100 mA g, and long cycle life (87% capacity retention over 300 cycles). The high reversibility of the P2-KCoO 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 KCoO cathodes and microspheres KCoO∥hard carbon full cells, but also provides new insights into the exploration of other layered metal oxides for PIBs.