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All-solid-state sodium-ion batteries (SSSIBs) prevent leakage and fire risks associated with liquid electrolytes by using non-flammable solid electrolytes and electrodes. The primary aim of this work is to develop a NASICON type ceramic electrolyte Na3Zr2Si2PO12 (NZSP) with co-doping of Mg2+ and Sc3+ to achieve high ionic conductivity. Mg2+ doping reduces the grain–grain boundary resistance by forming conducting phase NaMgPO4 across the grain boundaries. Co-substitution of a trivalent Sc3+ at the Zr4+ site compensates for Na deficiency. As a result, the Na ion mobility through grains and grain boundaries was increased with this co-doping of aliovalent Mg2+ and Sc3+. The highest grain and grain boundary ionic conductivities (σb ∼ 1.78 × 10−3 S cm−1 and σgb ∼ 0.4 × 10−3 S cm−1) and Na ion transference number (tNa+ ∼ 0.998) have been achieved for the optimized composition of Na3.3Zr1.8Mg0.10Sc0.10Si2PO12 (NZSP-0.1MS). The NZSP-0.1MS ceramic electrolyte is further employed in quasi-solid cells; a decent discharge capacity of 91 mA h g−1 at 0.1C rate was obtained for the "Zn doped (NVZP) (cathode)‖NZSP-0.1MS‖NVZP(anode)" ceramic full cell. The NZSP-0.1MS ceramic electrolyte filler is further incorporated into the polymer–salt matrix to develop the PEO–NaTFSI/NZSP-0.1MS composite electrolyte. The all-solid-state cell comprised of composite electrode (NVZP/NZSP-0.1MS/PVDF-NaTFSI/C) and composite electrolyte PEO–NaTFSI/NZSP-0.1MS delivered a maximum discharge capacity of 105 mA h g−1 at 0.1C, at 60 °C with good rate performance and cyclic stability retaining 85% capacity over 80 cycles. The specific capacity of the catholyte‖PEO–NaTFSI/NZSP-0.1MS‖anolyte full cell has further decreased to 78 mA h g−1 with a subsequent increase in the C-rate from 0.1 to 1C. Interestingly, the capacity was restored to 97 mA h g−1 after returning to 0.1C, which suggests a better electrochemical stability of the cell components. This study presents an all solid-state sodium-ion cell exhibiting superior electrochemical performances comparable to those of NVP-based liquid electrolyte full cells, providing an avenue for developing a high-performance and safe sodium-ion battery technology. [ABSTRACT FROM AUTHOR]

Mesoporous materials have received growing interest, particularly as electrode materials for lithium-ion battery applications since they provide short transportation length for Li ion and electrons, and favour electrolyte wettability. Such unique features are highly beneficial for improving the electrochemical performance of olivine LiFePO4 as this material has intrinsically low electronic and ionic conductivities, which otherwise would affect the storage performance. In addition, this sluggish kinetic brings about huge polarisation specifically at high current rates, resulting in poor energy efficiency. In order to overcome such kinetic issues, we present here a facile soft template-solvothemal method to synthesise mesoporous LiFePO4. Such mesoporous LiFePO4 is made of well interconnected nanograins (20–30 nm) which exhibits excellent storage performance and long-term cycling stability. In particular, the material shows improved storage performance at high rates with significantly less polarisation and clear signature of voltage plateaus for both Li ion insertion-extraction processes. In comparison with the LiFePO4 synthesized by the soft template method, the mesoporous LiFePO4 demonstrates excellent storage performance. This is attributed to the 2-D diffusion of both Li ions and electrons along b - and c -axes consistent with the 2-D Li ions transport reported previously for LiFePO4 single crystal. [ABSTRACT FROM AUTHOR]

We report here the heat generation and impedance characteristics of prototype 18650-sized sodium-ion cells using pristine Na3V2(PO4)3 (P-NVP) and modified Na3.2V1.8Zn0.2(PO4)3 (M-NVP) cathodes, hard carbon (HC) anode and an ether-based non-flammable electrolyte, 1 M NaBF4 in tetraglyme. Comparison of calorimetric studies performed on 18650-sized cells reveals lower heat generation in M-NVP versus HC compared to P-NVP versus HC owing to low internal resistance achieved as a result of Zn2+ doping in M-NVP. Both irreversible heat generation arose due to internal resistance and reversible heat generation caused by entropic changes in the electrode materials are elucidated. Furthermore, variation in subcomponents of internal resistance in both 18650-sized full cells and CR2016-sized half-cells is analysed by fitting electrochemical impedance spectra into equivalent circuit models. Individual contributions of anode and cathode to the impedance characteristics of the cells are determined by analysing impedance data of the half-cells using the distribution of relaxation times method. The results reveal lower diffusion resistance, as well as charge transfer resistance in M-NVP cells compared to P-NVP counterpart, accounting for the observed lower total internal resistance in M-NVP versus HC and thus lower heat generation in M-NVP versus HC cell than P-NVP versus HC cell. [ABSTRACT FROM AUTHOR]

P3-Na0.9Fe0.5Mn0.5O2 is reported as a new P-type cathode material for Na-ion batteries. The P3 structure can accommodate 0.9 mole of Na-ions leading to a high discharge capacity of 155 mA h g−1 and does not require sacrificial salts for full-cell operation. Operando X-ray diffraction and ex situ X-ray absorption studies are also reported. [ABSTRACT FROM AUTHOR]