A micro-cubic Prussian blue (PB) without coordinated water is first developed by electron exchange between graphene oxide and PB. The obtained reduced graphene oxide–PB composite exhibited complete redox reactions of the Fe sites and delivered ultrahigh electrochemical performances as well as excellent cycling stability as a cathode in sodium-ion batteries.

A structure optimized Prussian blue analogue Na1.76Ni0.12Mn0.88[Fe(CN)6]0.98 (PBMN) is synthesized and investigated. Coexistence of inactive Ni2+ (Fe–CN–Ni group) with active Mn2+/3+ (Fe–CN–Mn group) balances the structural disturbances caused by the redox reactions. This cathode material exhibits particularly excellent cycle life with high capacity (118.2 mA h g−1).

A high performance CoO/carbon nanofibers (CNF) composite catalyst was synthesized for Li-O2 batteries. For comparison, CoO/BP2000 and CoO/MWNTs were also prepared and investigated to study the influence of carbon supports on the electrochemical performance of the composite catalysts. Electrochemical tests showed that the Li-O2 battery with CoO/CNF demonstrated obviously enhanced electrochemical performance than the batteries with CoO/BP2000 and CoO/MWNTs catalysts, which delivered a first discharge capacity of 3882.5 mAh gcat−1 and remained about 3302.8 mAh gcat−1 after 8 cycles in the voltage range from 2.0 to 4.2 V. More importantly, the cycle stability of the Li-O2 battery with CoO/CNF could maintain over 50 cycles when cycled at a fixed capacity of 1000 mAh gcat−1. The unique porous nanofiberous structure of CoO/CNF greatly contributed to its high electrocatalytic performance.

A Na4Fe(CN)6/NaCl solid solution was synthesized and investigated as a cathode material for sodium ion batteries. Pure Na4Fe(CN)6 and NaCl do not work as cathode materials for sodium ion batteries, while a sample of Na4Fe(CN)6/NaCl demonstrated a remarkably enhanced Na+ insertion/extraction capability and electrochemical performance, due to the cation vacancies and interconnected cages generated in the solid solution framework.

•P2-Na2/3[Ni1/3Mn2/3]O2 was synthesized via spray drying method and a two step solid state process.•Cycling performance of P2-Na2/3[Ni1/3Mn2/3]O2 cathode was studied in different voltage ranges.•The prepared material showed excellent reversibility between 2.0 V and 4.0 V with good capacity retention.•Cycled in 2.0–4.5 V, the crystal structure of P2-Na2/3[Ni1/3Mn2/3]O2 was irreversibly damaged.•The discharge capacities increased to 134.7 mA g−1 (0.1 C) and 107.8 mA g−1 (1 C), cycled in 1.6–3.8 V.P2-type Na2/3[Ni1/3Mn2/3]O2 cathode material has been synthesized via spray drying method and a two step solid state process. Electrochemical behavior of the prepared material as cathode material for sodium ion battery was investigated in different charge-discharge voltage ranges. The results indicated that the cycling performance of the P2-Na2/3[Ni1/3Mn2/3]O2 cathode greatly depended on the voltage window. The material showed excellent reversibility between 2.0 V and 4.0 V with reversible capacity of 86 mAh g−1 (0.1 C) and 77 mAh g−1 (1 C). XRD analyses indicated that crystal structure of the P2-type Na2/3[Ni1/3Mn2/3]O2 could be well maintained after long term cycling in 2.0–4.0 V. When the upper limiting voltage was increased to 4.5 V, the crystal structure of P2-Na2/3[Ni1/3Mn2/3]O2 was irreversibly damaged due to over extraction of Na+ in 4.0–4.5 V. On the other hand, when the cycling voltage range was between 1.6 V and 3.8 V, the discharge capacities increased to 135 mAh g−1 (0.1 C) and 108 mAh g−1 (1 C), respectively. However, the cycling stability in 1.6–3.8 V was not as excellent as that in 2.0–4.0 V. This maybe due to the lattice stress caused by the over insertion of Na+ in the structure at lower voltage.

A novel Co(phen)2/C catalyst was prepared by coating cobalt(II) phenanthroline (phen) chelate on BP2000 carbon black and then heat treating in an inert atmosphere. The obtained Co(phen)2/C product with 1.0 wt% cobalt loading exhibits similar morphology and porosity characteristics to those of the bare BP2000. X-ray diffraction measurements demonstrate a face-centered cubic (fcc) α-Co phase embedded in the carbon support after pyrolysis. Charge/discharge tests of the lithium-oxygen cells using the prepared Co(phen)2/C catalyst show high discharge capacities of 4870 mAh g−1 (0.05 mA cm−2), 3353 mAh g−1 (0.1 mA cm−2) and 3220 mAh g−1 (0.15 mA cm−2), respectively. The Co(phen)2/C cathode exhibits reasonable reversibility with capacity retention of 1401 mAh g−1 (0.1 mA cm−2) after 10 cycles. The superior electrochemical performance of the prepared Co(phen)2/C catalyst and low cost of the phenanthroline chelating agent indicate that Co(phen)2/C is a promising cheap catalyst for lithium-air batteries.

ZnS/C composites were synthesized by a combined precipitation with carbon coating method. Morphology and structure of the as-prepared ZnS/C composite materials with carbon content of 4.6 wt%, 9.3 wt% and 11.4 wt% were characterized using TEM and XRD technique. TEM observation demonstrated that the ZnS/C (9.3 wt% C) composite showed excellent microstructure with 20–30 nm ZnS nanoparticles uniformly dispersed in conductive carbon network. Electrochemical tests showed that the ZnS/C (9.3 wt% C) composite presented superior performance with initial charge and discharge capacity of 1021.1 and 481.6 mAh/g at a high specific current of 400 mA/g, after 300 cycles, the discharge capacity of ZnS/C electrode still maintained at 304.4 mAh/g, with 63.2% of its initial capacity. The rate capability and low temperature performance of the ZnS/C (9.3 wt% C) composite were compared with commercial MCMB anode. The results showed that the ZnS/C (9.3 wt%) composite exhibited much better cycle capability and low temperature performance than MCMB anode. ZnS/C composite seems to be a promising anode active material for lithium ion batteries. Intercalation mechanism of the ZnS/C composites for lithium ion insertion–extraction is proposed based on the ex situ X-ray diffraction analysis incorporating with its electrochemical characteristics.

Low temperature performance of LiFePO4/C cathode was remarkably improved by slight Mn-substitution. Electrochemical measurements showed that about 95% of the discharge capacity of LiFe0.98Mn0.02PO4/C cathode at 20°C was obtained at 0°C, compared to 85% of that of LiFePO4/C cathode. The LiFe0.98Mn0.02PO4/C sample also presented enhanced rate performance at −20°C with the discharge capacities of 124.4 mA h/g (0.1C), 99.8 mA h/g (1C), 80.7mAh/g (2C) and 70 mA h/g (5C), respectively, while pristine LiFePO4/C only delivered capacities of 120.5 mA h/g (0.1C), 90.7 mA h/g (1C), 70.4 mA h/g (2C) and 52.2 mA h/g (5C). Cyclic voltammetry measurements demonstrated an obvious improvement of the lithium insertion-extraction process of the LiFePO4/C cathode by slight Mn-substitution. The results of FSEM observation and electrical conductivity measurement indicated that slight Mn-substitution minimized the particle size of LiFe0.98Mn0.02PO4/C and also obviously improved the electrical conductivity of the compound, thus obviously enhances the interface reaction process on the cathode.

Effects of ball milling way and time on the phase formation, particulate morphology, carbon content, and consequent electrode performance of LiFePO4/C composite, prepared by high-energy ball milling of Li2CO3, NH4H2PO4, FeC2O4 raw materials with citric acid as organic carbon source followed by thermal treatment, were investigated. Three ball milling ways and five different milling durations varied from 0 to 8 h were compared. LiFePO4/C composites could be obtained from all synthesis processes. TEM examinations demonstrated LiFePO4/C from ball milling in acetone resulted in sphere shape grains with a size of ∼60 nm, similar size was observed for LiFePO4/C from dry ball milling but in a more irregular shape. The ball milling in benzene resulted in a much larger size of ∼250 nm. The LiFePO4/C composites prepared from dry ball milling and ball milling in acetone showed much better electrochemical performance than that from ball milling in benzene. SEM examinations and BET measurements demonstrated that the high-energy ball milling effectively reduced the grain size. A ball milling for 4 h resulted in the best electrochemical performance, likely due to the proper amount of carbon and proper carbon structure were created.

A facile chemical polymerization method was applied to prepare LiFePO4/C-PPy composite using Fe(III)tosylate as oxidant. The as-prepared LiFePO4/C-PPy sample with PPy content of approximately 4 wt% showed great rate capability with a discharge capacity of 115 mAh/g at 20C. High temperate cycling performance of the LiFePO4/C-PPy sample was compared with bare LiFePO4/C at 5C charge–discharge rate at 55 °C. The LiFePO4/C-PPy cathode showed superior cycling stability with an initial capacity of 155 mAh/g. Ninety percentage of this initial capacity was retained after 300 cycles, compared to 40% of that of bare LiFePO4/C. The LiFePO4/C-PPy electrode showed stable discharge plateau voltage of 3.35–3.25 V vs. Li+/Li during long term cycling. The superior performance of the LiFePO4/C-PPy electrode was due to the enhanced electrical conductivity, negligible iron dissolution and alleviated electrode cracking contributed by PPy coating.

A structure optimized Prussian blue analogue Na1.76Ni0.12Mn0.88[Fe(CN)6]0.98 (PBMN) is synthesized and investigated. Coexistence of inactive Ni2+ (Fe–CN–Ni group) with active Mn2+/3+ (Fe–CN–Mn group) balances the structural disturbances caused by the redox reactions. This cathode material exhibits particularly excellent cycle life with high capacity (118.2 mA h g−1).

A micro-cubic Prussian blue (PB) without coordinated water is first developed by electron exchange between graphene oxide and PB. The obtained reduced graphene oxide–PB composite exhibited complete redox reactions of the Fe sites and delivered ultrahigh electrochemical performances as well as excellent cycling stability as a cathode in sodium-ion batteries.

A Na4Fe(CN)6/NaCl solid solution was synthesized and investigated as a cathode material for sodium ion batteries. Pure Na4Fe(CN)6 and NaCl do not work as cathode materials for sodium ion batteries, while a sample of Na4Fe(CN)6/NaCl demonstrated a remarkably enhanced Na+ insertion/extraction capability and electrochemical performance, due to the cation vacancies and interconnected cages generated in the solid solution framework.