Wenli Wei

Lithium-Oxygen (Li–O ₂ ) batteries offer the highest theoretical energy densities among current battery technologies, presenting immense potential for next-generation energy storage. However, progress in this field has been hindered by significant scientific and technical challenges, and the lack of standardised cell configurations, testing protocols, and reporting practices. This tutorial review provides a comprehensive overview of Li–O ₂ battery development, emphasising the importance of materials preparation, cell design and their impact on electrochemical performance. It also reviews key characterization techniques used in this field and their interpretation. To promote consistency and comparability across studies, a standardised testing procedure is proposed. The protocol is demonstrated through a comparative analysis of Li–O ₂ cells assembled using different cell configurations, while also highlighting the substantial impact that cell architecture alone can have on observed performance outcomes.

Conductive supports could improve the electrical conductivity of the electrode in lithium-sulfur (Li-S) batteries but suffer from the shuttle effect originated from the polysulfides dissolution, while the hydrophilic metal oxides could avoid the shuttle effect but with poor conductivity. Herein, a facile approach was developed to fabricate the hierarchically porous tin oxides (SnO2) nanoparticles anchored tubular polypyrrole (T-PPy) as sulfur host, in order to integrate the advantages of conductive supports and metal oxides but overcome their shortcomings. In the unique structure, the T-PPy nanotubes acted as conductive network to not only improve the electrical conductivity of cathodes but also accommodate the volume expansion of sulfur cathode during cycling as well as relatively confine the polysulfides diffusion, while the SnO2 nanoparticles served as high-efficient polysulfides trap to mitigate the shuttle effect due to the chemical bond between SnO2 and polysulfides. Moreover the hierarchically porous structure and therefore large surface area of the proposed S/(T-PPy)@SnO2 cathode were favorable for the accommodation of sulfur and lithium sulfides. Consequently, the S/(T-PPy)@SnO2 with 64.7% sulfur mass content exhibited excellent cyclic stability with a decay rate of only 0.05% per cycle along with 500 cycles at 1 C, rate capability of 383.7 mAh/g at 5 C, and coulombic efficiency above 90%, outstanding among most of the reported PPy-based sulfur cathodes and PPy-based ternary sulfur cathodes.

As a renewable energy technology, microbial fuel cell (MFC) has been attracting increasing attention in recent decades. However, practical applications of MFCs has been hampered by the unsatisfactory electrode performance, in particular, at the cathode. Herein, Fe/N/S‐doped carbon hollow tubes were prepared by a facile two‐stage procedure involving hydrothermal treatment and pyrolysis at controlled temperatures. Electrochemical studies showed that the obtained samples exhibited an apparent electrocatalytic activity towards oxygen reduction reaction in both alkaline and acidic media, a performance comparable to that of commercial Pt/C, and the sample prepared at 800 °C stood out as the best among the series with a half‐wave potential of +0.81 V vs. RHE and an electron transfer number of 3.98 at +0.6 V vs. RHE. The Fe/N/S‐doped carbon tubes also exhibited a remarkable performance as an MFC anode by facilitating bacterial growth and electron transfer between the biofilm and electrode. In fact, an MFC based on the carbon tubes as both cathode and anode showed a markedly higher performance (maximum power density 479 W m⁻³) than the control MFC based on a graphene aerogel anode and Pt/C cathode (359 W m⁻³). These results suggest that Fe/N/S‐doped carbon composites can be used for the fabrication of high‐efficiency MFC electrodes.

PPy-coated MnO₂ nanotubes were fabricated as a highly efficient sulfur host. Hollow interior of the MnO₂ nanotubes and the polypyrrole outer layer can effectively improve the specific capacity and maintain an extremely stable cycling performance.

Well-defined core–shell structured coaxial sulfur/polypyrrole tubular nanocomposites, polypyrrole nanotubes wrapped by uniform rough sulfur layers, were fabricated as Li–S battery cathodes via a facile one-pot method. In the designed structure, the polypyrrole backbone can facilitate the charge transport and also restrain the soluble polysulfide diffusion, while the active sulfur layer can efficiently react with Li⁺ assisted by the PPy nanotubes, and the lithium polysulfides can be massively trapped by the PPy nanotubes during charge–discharge processes. The as-prepared coaxial sulfur/polypyrrole tubular nanocomposites with a sulfur loading of 53.3% exhibited a high initial discharge specific capacity of 1117 mA h g⁻¹ with a remarkable cycling stability, retaining 692 mA h g⁻¹ and 525 mA h g⁻¹ after 200 cycles at a current density of 0.2C and 1C, respectively. Moreover, they expressed an excellent rate capability performance, maintaining 470 mA h g⁻¹ at a high current density of 2C.