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Bulk magnetic refrigerant materials with first-order character usually possess hysteresis losses and concentrated refrigeration working temperature interval (δTFWHM), which are detrimental for magnetic refrigeration applications. Here, we report on Ni-Mn-Ga micro-particles with size ~38.5–45 μm fabricated by grinding and subsequent stress relief annealing (SRA). The microstructure, martensite transformation (MT), hysteresis loss and magnetocaloric effect (MCE) of the SRA particles were studied in comparison with the bulk alloy counterpart. The thermal and magnetic hysteresis losses in SRA particles ~1.3 K and ~1.9 J/kg were significantly reduced compared to those in the bulk alloy ~5.5 K and ~9.7 J/kg, respectively, which is related to the reduction of neighboring grain constraints on martensite/austenite phase boundary motion. The MT transformation temperature range of the SRA particles ~26.5 K was higher than that of the bulk alloy ~5.5 K because of the high specific surface area of the particles and the residual internal stress after SRA. A magneto-structural partly-coupled state was attained in the SRA particles, which is responsible for the wide δTFWHM ~25 K and the high refrigeration capacity (RCnet) ~117 J/kg. Based on these results, a possible approach for the high magnetic refrigeration efficiency is expected and discussed. Keywords: Magnetocaloric effect (MCE), Refrigeration capacity (RC), Particle, Martensite transformation, Hysteresis loss, Ni-Mn-Ga alloy

Solid-state electrolytes have become a promising approach for rechargeable lithium batteries with enhanced safety and high energy density. However, the rigid nature of ceramic electrolytes would result in the poor interfacial contact, and polymer electrolytes suffer from inferior electrochemical performance and unsatisfied mechanical strength to suppress Li dendrites. In this work, we report a flexible Li1.3Al0.3Ti1.7(PO4)3 (LATP)-reinforced polyvinylidene fluoride (PVDF)-based solid composite electrolyte with superior performances in terms of high ionic conductivity (1.64 × 10−3 S cm−1 at room temperature), high lithium transference number (0.45), wide electrochemical window (0–4.76 V) and enhanced tensile strength (14.2 MPa). The existence of LATP permits the utilization of high Li-salt content which increases the charge carrier concentration. Meanwhile, LATP facilitates the Li+ conduction process and enhances the mechanical strength, leading to a long-term electrochemical stability of symmetric Li cell for 600 h at 0.2 mA cm−2. Assembled with LiFePO4 cathode, the all-solid-state Li battery delivers a high capacity of 153.7 mA h g−1 at 0.3 C with remarkable cycle stability. This work provides a bright future for composite polymer electrolytes in the application of all-solid-state lithium batteries.

Composite solid electrolyte (CSE) consisting of Li+ conductive fillers and polymer matrix has become attractive for high energy-density lithium batteries. Current researches focus on the “ceramic in polymer”-type CSE due to the severe agglomeration of ceramic particles. Consequently, the destroyed percolation network impedes the further improvement in ionic conductivity. In this work, we report a novel structural design of ceramic-enriched CSE consisting of three-dimensional (3D) interconnected Li1.3Al0.3Ti1.7(PO4)3 (LATP), polyvinylidene fluoride (PVDF) and LiN(SO2)2(CF3)2 (LiTFSI). The 3D LATP network is constructed through the surface functionalization of LATP particles by polymethyl methacrylate (PMMA). Owing to the intermolecular interaction between PMMA and PVDF, the incorporation of PMMA-coated LATP (denoted as LATP@PMMA) enables the uniform distribution of ceramic phase and generates interconnected LATP network. Noticeably, such an electrolyte maximizes the utilization of inorganic fillers through the facile treatment of zero-dimensional materials, which is comparable to those 3D template-derived fillers. Furthermore, continuous Li+ conduction pathways through LATP framework and LATP/PVDF interphase are guaranteed by the enhanced affinity of LATP towards PVDF matrix and the intrinsic Li+ complexation capability of PMMA. Remarkable cycling performances of the LiNi0.5Co0.2Mn0.3O2/LATP@PMMA-PVDF/Li batteries confirm the feasibility of 3D ceramic-enriched composite electrolyte in the application of solid-state lithium batteries.