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Potassium-ion batteries (KIBs) have attracted great attention due to their unique advantages including abundant resources, low redox potential of K, and feasible usage of cheap aluminum current collector in battery assembly. In the present work, through first-principles calculations, we find that the recently synthesized two-dimensional T-NiSe2 is a promising anode material of KIBs. It possesses a large capacity (247 mAh/g), small diffusion barrier (0.05 eV), and low average voltage (0.49 V), rendering T-NiSe2 a high-performance KIB anode candidate. In addition, we analyze the carrier mobility of T-NiSe2, and the results demonstrate that it possesses a superior carrier mobility of 1685 cm2/(V s), showing the potential for applications in nanoelectronic devices.

Potassium-ion batteries (KIBs) are emerging as the prospective alternatives to lithium-ion batteries in energy storage systems owing to the sufficient resources and relatively low cost of K-related materials. However, serious volume expansion and low specific capacity are found in most materials systems resulting from the large intrinsic radius of K + . Herein, SnS 2 nanosheets anchored on nitrogen and sulfur co-doped MXene (SnS 2 NSs/MXene) are creatively designed as advanced anode materials for KIBs. SnS 2 NSs/MXene with a unique hierarchical structure can not only provide fast transmission channels for K + but also avoid the accumulation of K + and volume expansion. These novel features make SnS 2 NSs/MXene electrodes exhibit a superior reversible specific capacity of 342.4 mA h g −1 under 50 mA g −1 . Also, they maintain 206.1 mA h g −1 at an even higher current density of 0.5 A g −1 over 800 cycles almost without capacity decay. Moreover, the multistep alloying reaction mechanism of SnS 2 NSs/MXene composites and K + is revealed by the ex situ Xray diffraction measurement. In addition, the density functional theory calculations confirm the existence of Ti−S bonds between SnS 2 nanosheets and MXene, which significantly enhance the structural stability and cycling electrochemical performance of SnS 2 NSs/MXene composites.

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Laser cooling of mesoscopic mechanical resonators is of great interest for both fundamental studies and practical applications. We provide a general framework to describe the cavity-assisted backaction cooling in the strong coupling regime. By studying the cooling dynamics, we find that the temporal evolution of mean phonon number oscillates as a function of the optomechanical coupling strength depending on frequency mixing. The further analytical result reveals that the optimal cooling limit is obtained when the system eigenmodes satisfy the frequency matching condition. The reduced instantaneous-state cooling limits with dynamic dissipative cooling approach are also presented. Our study provides a guideline for optimizing the backaction cooling of mesoscopic mechanical resonators in the strong coupling regime.

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Developing advanced electrode materials for potassium-ion batteries (PIBs) is an emerging research area in recent years; so far, several strategies such as heteroatom doping into carbon, increasing interlayer spacing, or creating amorphous region in graphite have been investigated. Here, we studied the effect of sub-nanopores in a porous-carbon aerogel with a pore size distribution centered at around 0.8 nm and achieved outstanding PIB performance including long cycling stability (particularly at small current densities for prolonged charge/discharge period) and high rate capability with enhanced retentions. Mechanism studies reveal very high contribution from surface capacitive potassium (K)-ion storage (more than 90%) to the total capacity, and theoretical calculations show that 0.8 nm sub-nanopores lead to substantially low barrier for K-ion transport and storage, with ultrasmall diffusion energy and negligible lattice change. Sub-nanopore engineering, as demonstrated here, may be adopted to develop highly efficient and stable porous-carbon-based structures for applications in advanced energy storage systems and electrochemical catalysis.

Copper chalcogenides have attracted much attention in recent years because of their promising applications in thermoelectric conversion. However, many of them suffer from phase transformation at low temperature. Motivated by the synthesis of bulk β‐CsCu5Se3 with high phase transformation temperature of 923 K for photovoltaic applications, its thermoelectric properties using first‐principles calculations combined with Boltzmann transport theory are systematically studied. The results show that β‐CsCu5Se3 possesses ultralow lattice thermal conductivities of 0.24, 0.41, and 0.25 W mK−1 along the x, y, and z directions at room temperature, respectively, which are further reduced to 0.09, 0.15, and 0.09 W mK−1 at 800 K. A detailed analysis of its group velocity, three phonon scattering rate, Grüneisen parameter and three phonon phase space reveals that the weak harmonicity and strong phonon anharmonic scattering are responsible for the ultralow lattice thermal conductivity, leading to a high figure of merit (ZT) value of 1.81 along the y direction at 800 K, which is three times higher than that of known thermoelectric materials o‐CsCu5S3 (0.46 at 800 K) and t‐CsCu5S3 (0.56 at 875 K). This study suggests that β‐CsCu5Se3 is a multifunctional material promising for both photovoltaic and thermoelectric applications.