Thick electrode, with its feasibility and cost-effectiveness in lithium-ion batteries (LIBs), has attracted significant attention as a promising approach maximizing the energy density of battery. Through raising the mass loading of active materials without altering the fundamental chemical attributes, thick electrodes can boost the energy density of the batteries effectively. Nevertheless, as the thickness of the electrode increases, the ionic conductivity of the electrode decreases, leading to abominable polarization in the thickness direction, which severely hampers the practical application of a thick electrode. This work proposes a novel porous gradient design of high-performance thick electrodes for LIBs. By constructing a porous structure that serves as a fast transport pathway for lithium (Li) ions, the ion transport kinetics within thick electrodes are significantly enhanced. Meanwhile, a particle size gradient design is incorporated to further mitigate polarization effects within the electrode, leading to substantial improvements in reaction homogeneity and material utilization. Employing this strategy, we have fabricated a porous gradient nanocellulose-carbon-nanotube based thick electrode, which exhibits an impressive capacity retention of 86.7% at a high mass loading of LiCoO₂ (LCO) active material (20 mg cm⁻²) and a high current density of 5 mA cm⁻².

The development of earth-abundant-metal-based electrocatalysts with high efficiency and long-term stability for hydrogen evolution reaction (HER) is crucial for the clean and renewable energy application. Herein, we report a molten-salt method to synthesize Co-doped CaMn₃O₆ (CMO) nanowires (NWs) as effective electrocatalyst for HER. The as-obtained CaMn_3−xCo_xO₆ (CMCO) exhibits a small onset overpotential of 70 mV, a required overpotential of 140 mV at a current density of 10 mA·cm⁻², a Tafel slope of 39 mV·dec⁻¹ in 0.1 M HClO₄, and a satisfying long-term stability. Experimental characterizations combined with density functional theory (DFT) calculations demonstrate that the obtained HER performance can be attributed to the Co-doping which altered CMO’s surface electronic structures and properties. Considering the simplicity of synthesis route and the abundance of the pertinent elements, the synthesized CMCO shows a promising prospect as a candidate for the development of earth-abundant, metal-based, and cost-effective electrocatalyst with superior HER activity. Our results also establish a strategy of rational design and construction of novel electrocatalyst toward HER by tailoring band structures of transition metal oxides (TMOs).

Metallic tin (Sn) foil is a promising candidate anode for lithium-ion batteries (LIBs) due to its metallurgical processability and high capacity. However, it suffers low initial Coulombic efficiency and inferior cycling stability due to its uneven alloying/dealloying reactions, large volume change and stress, and fast electrode structural degradation. Herein, we report an undulating LiSn electrode fabricated by a scalable two-step procedure involving mechanical lithography and chemical prelithiation of Sn foil. With the combination of experimental measurements and chemo-mechanical simulations, it was revealed the obtained undulating LiSn/Sn electrode could ensure better mechanical stability due to the pre-swelling state from Sn to Li_xSn and undulating structure of lithography in comparison with plane Sn, homogenize the electrochemical alloying/dealloying reactions due to the activated surface materials, and compensate Li loss during cycling due to the introduction of excess Li from Li_xSn, thus enabling enhanced electrochemical performance. Symmetric cells consisting of undulating LiSn/Sn electrode with an active thickness of ~5 um displayed stable cycling over 1000 h at 1 mA cm^-2 and 1 mAh cm^-2 with a low average overpotential of <15 mV. When paired with commercial LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622) cathode with high mass loading of 15.8 mg cm^-2, the full cell demonstrated a high capacity of 2.4 mAh cm^-2 and outstanding cycling stability with 84.9% capacity retention at 0.5 C after 100 cycles. This work presents an advanced LiSn electrode with stress-regulation design toward high-performance LIBs, and sheds light on the rational electrode design and processing of other high-capacity lithium alloy anodes.