K–Se batteries follow distinctive reaction pathways in concentrated ether electrolytes, and deliver record-high discharge plateau voltage of 1.85 V on average and energy density of 998 W h kg_Se⁻¹, both approaching the theoretical limits.

Significance: Diamond is an essential material for industrial and scientific applications due to its exceptional properties. The regulation of diamond performance through microstructural design is a challenging and hot topic. Here, we report the synthesis of diamond with preferentially oriented nanotwin bundles via direct phase transformation of superaligned multiwalled carbon nanotube films under high temperature and pressure. The preferentially oriented nanotwin bundles endow diamond with the highest hardness anisotropy ever recorded and a record hardness value in the direction perpendicular to the oriented nanotwin bundles. Current findings provide valuable insights on the microstructural design and modification of diamond and related materials, contributing to the further tuning of properties in the future.

Ganymede has strong evidence of a subsurface ocean primarily composed of MgSO₄. We conducted experimental measurements of the electrical conductivity of aqueous MgSO₄ at 200–1,200 MPa and 243–295 K in a multianvil press, simulating the high‐pressure and low‐temperature (HPLT) conditions of Ganymede's subsurface ocean. A numerical model is proposed with logσ = − 3.1605+940.931/T+0.8986logc+2logΛ⁰ − log(5Λ⁰+2695c^1/2), where σ is electrical conductivity in S/m, T is temperature in K, c is molar concentration in mol/L, and Λ⁰ is limiting equivalent conductance in S·cm²·equiv⁻¹. We used this model to generate electrical conductivity curves up to 500 km deep in Ganymede and found that the values are lower than previously predicted. Our novel experimental methods demonstrate access to the HPLT environment of liquid samples that expands our ability for experimental simulation of icy ocean worlds in the outer solar system.