Compared to the state‐of‐art lithium‐ion batteries, the all‐solid‐state batteries offer improved safety along with high energy and power density. Although considerable research has been conducted, the inherent problems arising from solid electrolytes and the lack of suitable electrolytes hinder their development in practical applications. Furthermore, traditional synthesis routes have drawbacks due to limited control to fabricate the solid electrolytes with desired shape and size, impeding their maximum performance. In recent years, additive manufacturing or three‐dimensional (3D) printing techniques have played a vital role in constructing solid‐state batteries because of the rational design of functional electrode and electrolyte materials for batteries with increased performance. 3D printing in batteries may provide a new technology solution for existing challenges and limitations in emerging electronic applications. This process boosts lithium‐ion batteries by creating geometry‐optimized 3D electrodes. 3D printing offers a range of advantages compared to traditional manufacturing methods, including designing and printing more active and passive components (cathodes, anodes, and electrolytes) of batteries. 3D printing offers desired thickness, shape, precise control, topological optimization of complex structure and composition, and a safe approach for preparing stable solid electrolytes, cost‐effective and environmentally friendly.

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A nanostructured n-type Bi2Te2.7Se0.3 (BTS) alloy with a unique microstructure was prepared using a facile melting-rotation-quenching process followed by ball-milling and uniaxial hot-press sintering at 623 K. Anisotropy in the resulting microstructure showed anisotropic electrical and thermal transport properties in two directions normal to the pressing axis. The texture of the nanostructured BTS alloy was analyzed by x-ray diffraction and scanning electron microscopy. Based on the geometric phase analysis of a high resolution transmission electron microscopy images, abundant dislocations, high grain boundary density, and oxide impurity were identified, which act as phonon scattering centers. Higher anisotropy in thermal conductivity combined with oxide impurity resulted in an ultra-low phonon thermal conductivity of ∼0.305 W mK−1 at 423 K in the nanostructured n-type BTS in the direction parallel to the pressing axis. Laser power- and temperature-dependent Raman spectra analyses provided a deeper insight into the anisotropy in thermal transport properties. Optimum power factor and low thermal conductivity, due to the combination of grain alignment and oxide impurity, resulted in a dimensionless figure of merit (zT ) value of ∼0.75 at 423 K. In comparison, the high and opposite temperature dependences of electrical conductivity and thermal conductivity led to a better average zT value of ∼0.68 and a thermoelectric energy conversion efficiency percentage of ∼4.4% in the operating temperature range (300–423 K) in the direction parallel to the pressing axis.

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The dual-doped Ca1–x RE′ x/2RE″ x/2MnO3 (RE′/RE” = Dy, Gd, Yb, Lu; 0.05 ≤ x ≤ 0.1) based n-type thermoelectric oxides were synthesized by the sol–gel methodology. The sol–gel method of synthesis lowered the sintering temperature; this enhanced the density of the system close to the theoretical value. Rare-earth doping at the Ca site drastically reduced the electrical resistivity by 2 orders of magnitude, compared to that of undoped CaMnO3. This was due to the formation of Mn3+ (t2g 3eg 1) ions with eg 1 electrons in the Mn4+ (t2g 3e g 0) matrix of Ca1–x RE′ x/2RE″ x/2MnO3. The temperature dependence of electrical resistivity revealed a change from semiconductor to metallic at lower doping levels (Ca0.95RE′0.025RE″0.025MnO3), while at higher doping levels (Ca0.9RE′0.05RE″0.05MnO3) the ρ­(T) curve had a semiconducting nature in the entire temperature range. In contrast, the Seebeck coefficient showed linear temperature dependence for all the compositions. The power factor (PF) of Ca1–x RE′ x/2RE″ x/2MnO3 (RE′/RE” = Dy, Gd, Yb, Lu; 0.05 ≤ x ≤ 0.1) was much higher than the PF of undoped CaMnO3 and the highest PFs obtained were 530 μW m–1 K–2 for Ca0.95Dy0.025Yb0.025MnO3 and 580 μW m–1 K–2 for Ca0.9Lu0.05Yb0.05MnO3 at 950 K. The proof-of-concept experiment of power generation with Ca3Co4O9 as p-type element resulted in a power output of 160 μW at 500 °C for a unicouple module.