Mg₃Sb₂-based n-type Zintl compounds have attracted greater attention for their superior thermoelectric performance, making them a potential candidate for medium-temperature (< 900 K) applications. Herein, this work verifies the p-type Mg_1.8Zn_1.2Sb₂ solid-solution and defect engineering could be the key mechanism to reduce the lattice thermal conductivity (κ_L) for improving the thermoelectric performance. The carrier and phonon transport properties were studied by adding heavy element Ag at Mg-sites of Mg_1.8Zn_1.2Sb₂ solid-solution. As a result, the Ag_0.03Mg_1.77Zn_1.2Sb₂ sample simultaneously obtained the maximum power factor of 456 μW/mK² via band convergence and defect engineering, which led to reduced thermal conductivity of 0.56 W/mK at 753 K by the strengthening of multiscale phonon scattering. In addition, optimized carrier density and thermal conductivity resulting in a maximum figure of merit (zT) of 0.5 at 753 K has been obtained for Ag_0.03Mg_1.77Zn_1.2Sb₂, which is 285% higher than undoped Mg_1.8Zn_1.2Sb₂. This work demonstrates that heavy element substitution induces band convergence and that defect engineering leads to simultaneous improvement in thermoelectric transport properties of p-type Mg_1.8Zn_1.2Sb₂.

The nickel-rich NMC₉₅₅ (LiNi_0.90Mn_0.05Co_0.05O₂) cathode, with minimal cobalt, is the zenith of LiNi_xMn_yCo_1-x-yO₂ (NMC) technology but faces structural and thermal stability challenges, losing an average of 15% of its capacity in the first discharge. Here, by selecting appropriate materials and synthesis methods in an all-solid-state battery cell, this challenge is effectively mitigated. A sustainable fabrication of the LiNMC₉₅₅ positive electrode, excluding poly(vinylidene fluoride) (PVDF) and using styrene-butadiene rubber, demonstrates high retention inall-solid-state cells,without additional interlayers or pressure, at room temperature. To prevent oxygen release, spurious phase formation, and magnetic frustration, simulations determined optimal cycling thresholds and curve morphologies for a Li⁰/Li₆PS₅Cl/NMC₉₅₅ cell by “following the electrons”. This optimized routine ensures prolonged cycle life and performance demonstrated by sheet resistance/Hall effect, Scanning Electron Microscopy/Energy-Dispersive X-ray Spectroscopy (SEM/EDX), Atomic Force Microscopy/Scanning Kelvin Probe Microscopy,Time-of-FlightSecondary Ion Mass Spectrometry, Raman, calorimetry, and electrochemical analyses. The tailored preparation method and cycling regimen enabled the fabrication of a high-performance cathode, achieving capacities exceeding 110-120 mAh.g^-1 at C discharging C-rate, after 200 cycles, with a self-recovering component shifting performance to theoretical capacities (192 mAh.g^-1), emphasizing the cathode's pivotal role in all-solid-state performance.