Transition metal borides Co–B and Co–Ni–B are prepared by a simple chemical reduction method and used to construct a new all-boride aqueous solution battery with borides used for both the anode and cathode. This all-boride-based battery exhibits an excellent electrochemical property and extreme frost tolerance. The results of the electrochemical performance test demonstrate that the specific capacity of this all-boride battery reaches 332.4 mA h g–1 at a current density of 500 mA g–1 and is maintained at 280 mAh g–1 with a high discharge current density of 8 A g–1 as a result of the rapid electrochemical reaction kinetics and high electronic conductivity. This all-boride battery can continue to work at low temperatures (−40 °C) and exhibits good electrochemical performance; therefore, it can be used under extreme cold weather conditions. The electrode material of the all-boride battery is simple to prepare, is energy-saving, does not require special equipment or a special environment during assembly, and thus shows promise as a new energy storage device.

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Transition-metal/heteroatom-doped carbon exhibits exceptional oxygen reduction reaction (ORR) catalytic activity in alkaline electrolytes, which is expected to replace noble metals as fuel cell cathode catalysts. The ORR activity of catalysts can be further improved by enriching active sites and enhancing the intrinsic activity of catalysts. Herein, phosphorus-rich porous polyaniline (P-PANi) gel is used as a precursor during heat treatment, and the characteristics of low boiling point (about 200 °C) and steric hindrance of ferrocene are introduced to synthesize high-dispersion iron-doped graphite catalysts. A series of as-synthesized Fe-N/P/C catalysts were obtained at various heat treatment temperatures. Fe-N/P/C-850 manifests the highest ORR activity and electrochemical stability, with an onset potential of 1.06 V and a half-wave potential of 0.86 V. The enhanced activity of Fe-N/P/C-850 is mostly attributed to the P–C junction due to the combination of phosphorus and carbon.

Electrochemical impedance spectroscopy (EIS) is selected as the main investigation method to study the underlying mechanisms and electrochemical kinetics of a polyimide anode material for lithium-ion batteries (LIBs) through obtaining the primary parameters of Ohmic impedance (R s ), solid-electrolyte-interphase (SEI) impedance (R f ), and charge-transfer resistance (R ct ). A typical polyimide (PNDA) anode material is synthesized using a simple one-step high-temperature polymerization method. The EIS spectrum of PNDA is fitted by two different equivalent circuit models. Charge-transfer activation energies before cycling and after the first cycle are 51.52 and 39.55 kJ mol −1 , respectively, implying a large energy barrier for the discharge of PNDA. The R ct and R f are the key factors influencing the electrochemical performance of PNDA. However, R s exhibits a slight effect on the total electrochemical kinetics. It shows a decreasing trend with increasing operation temperature, but this positive effect could be almost negligible compared to the kinetics of the total electrochemical processes of lithium embedding. The R ct drops significantly with increasing temperature, reflecting a strong dependence of the charge-transfer process on temperature. However, R f displays a noticeable increment with temperature, indicating that the SEI on the PNDA is slightly unstable with elevated temperature even below 80 °C. This value is also commonly regarded as the critical temperature for stable SEI on carbon and silicon anodes. The extent of decrease of R ct with increasing temperature is far greater than that of R f increment, resulting in enhanced total electrochemical kinetics of PNDA with temperature increase, thus enhancing its electrochemical properties at elevated temperature. These parameters of EIS reflect the rate-control step of the electrode-reaction processes and give an evaluation of the electrode-reaction processes. The revealed determining factors of polyimides as anode materials could provide useful insights for the development of high-performance organic electrode materials for LIBs.