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Well-crystallized maricite NaFePO4 is thermodynamically stable but electrochemically inactive toward sodium owing to the close packed framework. An efficient activation-approach is to construct amorphous composites with carbon by the complex and energy-intensive synthetic process. Here, a facile approach was proposed by the combination of low-temperature sintering and ball milling, which is environmentally friendly and suitable for scalable synthesis. Quasi-amorphous maricite NaFePO4 was first prepared via reducing the calcination temperature to 350 °C. Amorphous composite NaFePO4/C was further obtained by ball milling of NaFePO4-350 °C with super P, which delivers a reversible capacity of 134 mAh g−1, closing to its theoretical capacity. More impressively, the NaFePO4/C electrode still demonstrates decent capacity-retention of ∼75.4% over 1000 cycles, which is encouraging for future research. Pairing with hard carbon anode, the (+)NaFePO4/C//HC(−) sodium-ion full cell delivers outstanding power density (169.9 Wh kg−1 calculated based on the total mass of positive and negative electrodes) and excellent cycling stability (84.5% capacity retention after 500 cycles at 5C), exhibiting powerful competitiveness compared with previously reported NaFePO4 based sodium-ion full cells. These results demonstrate the practical potential of maricite NaFePO4 cathode through low-temperature sintering.

With inspiration from the enhancement of the viscoelasticity of cellulose nanocrystals (CNCs) on hydrogels, we paid attention to cellulose fracturing fluids prepared from the CNCs skeleton reinforced covalently cross-linked cellulose networks. In this paper, we hybridized CNCs with sodium CMC-Na to form nano cellulose fracturing fluids, characterized the performance of nano hybrid fracturing fluids and analyzed the nano-crystals enhancing fracturing fluid performance mechanism. It showed that the apparent viscosity, temperature tolerance, elastic modulus, and tensile strength of cellulose fracturing fluids were improved by CNCs. Compared with the blank cellulose fracturing fluids, the viscosity value of nano-cellulose fracturing fluids at 120 ℃ reached 195mPa·s, with an increase of 200 %, and the elastic modulus was 30Pa, with an increase of about 253 %. Furthermore, the microscopic analysis revealed that CNCs can play the role of nucleus and skeleton in the network structure of cellulose fracturing fluids and obviously enhanced the strength of the network structure. It is obvious to improve the performance of the fracturing fluids by adding CNCs into the cellulose fracturing fluids. This method provides a new idea for the development of fracturing fluids suitable for unconventional reservoirs.

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