Industrially prepared artificial graphite (AG) is attractive for potassium-ion batteries (PIBs), but its rate performance is poor and the production process is energy intensive, so developing an efficient strategy to produce novel graphite with low energy consumption and high performance is economically important. Herein, a nanostructured graphite composed of multi-walled carbon nanotubes (MWCNTs) and graphite shells was prepared by one-pot method through low-temperature pyrolysis of iron-based metal-organic framework (MOF) and carbon source. The high graphitization degree of nanostructured graphite makes the initial Coulombic efficiency (ICE) exceed 80%, and the three-dimensional (3D) conductive network ensures a specific capacity of 234 mAh·g⁻¹ after 1000 cycles at a high current density of 500 mA·g⁻¹. In addition, the typical graphite potassium storage mechanism is also demonstrated by in situ X-ray diffraction (XRD) and in situ Raman spectroscopy, and its practicality is also proved by the voltage of the full cells. This work provides a feasible way to optimize the practical production process of AG and expand its application in energy storage.

The development and application of high performance potassium ion batteries (PIBs) is a major demand for China's strategic emerging industries, and it is also a new system and direction for the development of energy storage secondary batteries. However, the current research on PIBs is still in its initial stage, and still faces the challenges of slow diffusion kinetics, unclear transport mechanism, rapid capacity decay and difficulty in revealing the intrinsic decay mechanism. This paper summarizes the latest research results of the National Natural Science Foundation of China (NSFC) project "Surface/Interface Tuning and In Situ Interaction Mechanism of Hierarchical Mesoporous Nanowire Cathodes for Potassium Ion Battery", systematically describes the key scientific problems and technical bottlenecks in PIB research, and points out the efficient strategies to solve these problems and bottlenecks.

Aqueous zinc ion batteries (AZIBs) are ideal candidates for large-scale battery storage, with a high theoretical specific capacity, ecological friendliness, and extremely low cost but are strongly hindered by zinc dendrite growth. Herein, Ni-Zn alloy is artificially constructed as a solid-electrolyte interface (SEI) for Zn anodes by electrodeposition and annealing. The Ni-Zn alloy layer acts as a dynamic shield at the electrode/electrolyte interface. Interestingly, the zinc atoms migrate out of the electrode body during zinc stripping while merging into the electrode body during the plating. In this way, the Ni-Zn alloy is able to guide the zinc deposition in the horizontal direction, thereby suppressing the formation of dendrite. Benefiting from those, the Ni-Zn alloy symmetric cell shows a greatly improved cycle life and is able to operate stably for 1,900 h at a current density of 0.5 mA·cm⁻². The present study is a strategy for negative electrode protection of AZIBs.

The Fe–N–C material represents an attractive oxygen reduction reaction electrocatalyst, and the FeN₄ moiety has been identified as a very competitive catalytic active site. Fine tuning of the coordination structure of FeN₄ has an essential impact on the catalytic performance. Herein, we construct a sulfur-modified Fe–N–C catalyst with controllable local coordination environment, where the Fe is coordinated with four in-plane N and an axial external S. The external S atom affects not only the electron distribution but also the spin state of Fe in the FeN₄ active site. The appearance of higher valence states and spin states for Fe demonstrates the increase in unpaired electrons. With the above characteristics, the adsorption and desorption of the reactants at FeN₄ active sites are optimized, thus promoting the oxygen reduction reaction activity. This work explores the key point in electronic configuration and coordination environment tuning of FeN₄ through S doping and provides new insight into the construction of M–N–C-based oxygen reduction reaction catalysts.

Advances in electrochemical energy storage technologies drive the need for battery safety performance and miniaturization, which calls for the easily processable polymer electrolytes suitable for on-chip microbattery technology. However, the low ionic conductivity of polymer electrolytes and poor-patternable capabilities hinder their application in microdevices. Herein, we modified SU-8, as the matrix material, by poly(ethylene oxide) (PEO) with lithium salts to obtain a patternable lithium-ion polymer electrolyte. Due to the highly amorphous state and more Li-ion transport pathways through blending effect and the increase in number of epoxides, the ionic conductivity of achieved sample is increased by an order of magnitude to 2.9 × 10⁻⁴ S·cm⁻¹ in comparison with the SU-8 sample at 50 °C. The modified SU-8 exhibits good thermal stability (> 150 °C), mechanical properties (elastic modulus of 1.52 GPa), as well as an electrochemical window of 4.3 V. Half-cell and microdevice were fabricated and tested to verify the possibility of the micro-sized on-chip battery. All of these results demonstrate a promising strategy for the integration of on-chip batteries with microelectronics.

Aqueous zinc ion batteries have been considered as the prominent candidate in the next-generation batteries for its low cost, safety and high theoretical capacity. Nonetheless, formation of zinc dendrites and side reactions at the electrode/electrolyte interface during the zinc plating/stripping process affect the cycling reversibility of the zinc anode. Regulation of the zinc plating/ stripping process and realizing a highly reversible zinc anode is a great challenge. Herein, we applied a simple and effective approach of controlled-current zinc pre-deposition at copper mesh. At the current density of 40 mA cm⁻², where the electron/ion transfers are both continuous and balanced, the Zn@CM-40 electrode with the (002) crystal plane orientation and the compactly aligned platelet morphology was successfully obtained. Compared with the zinc foil, the Zn@CM-40 exhibits greatly enhanced reversibility in the repeated plating/stripping (850 h at 1 mA cm⁻²) for the symmetric battery test. A series of characterization techniques including electrochemical analyses, XRD, SEM and optical microscopy observation, were used to demonstrate the correlation between the structure of pre-deposited zinc layer and the cycling stability. The COSMOL Multiphysics modeling demonstrates a more uniform electric field distribution in the Zn@CM than the zinc foil due to the aligned platelet morphology. Furthermore, the significant improvement is also achieved in a Zn||MnO₂ full battery with a high capacity-retention (87% vs 47.8%). This study demonstrates that controlled-current electrodeposition represents an important strategy to regulate the crystal plane orientation and the morphology of the pre-deposited zinc layer, hence leading to the highly reversible and dendrite-free zinc anode for high-performance zinc ion batteries.

Surface modification of graphene oxide (GO) is a powerful strategy to develop its energy density for electrochemical energy storage. However, pre-modified GO always exhibits unsatisfactory hydrophilia and its ink-relevant utilization is extremely limited. Although GO ink is widely utilized in fabricating micro energy storage devices via extrusion-based 3D-printing, simultaneously obtaining satisfactory hydrophilia and high energy density still remains a challenge. In this work, an in-situ surface engineering strategy was employed to enhance the performance of GO micro-supercapacitor chips. Three dimensionally printed GO micro-supercapacitor chips were treated with pyrrole monomer to achieve selective and spontaneous anchoring of polypyrrole on the microelectrodes without affecting interspaces between the finger electrodes. The interface-reinforced graphene scaffolds were edge-welded and exhibited a considerably improved specific capacitance, from 13.6 to 128.4 mF·cm⁻². These results are expected to provide a new method for improving the performance of micro-supercapacitors derived from GO inks and further strengthen the practicability of 3D printing techniques in fabricating energy storage devices.

Aqueous rechargeable zinc ion batteries (ARZIBs) have received unprecedented attention owing to the low cost and high-safety merits. However, their further development and application are hindered by the issues of electrodes such as cathode dissolution, zinc anode dendrite, passivation, as well as sluggish reaction kinetics. Designing heterostructure electrodes is a powerful method to improve the electrochemical performance of electrodes by grafting the advantages of functional materials onto the active materials. In this review, various modified heterostructure electrodes with optimized electrochemical performance and wider applications are introduced. Moreover, the synergistic effect between active materials and functional materials are also in-depth analyzed. The specific modification methods are divided into interphase modification (electrode-electrolyte interphase and electrode-current collector interphase) and structure optimization. Finally, the conclusion and future perspective on the optimization mechanism of functional materials, and the cost issue of practical heterostructure electrodes in ARZIBs are also proposed. It is expected that this review can promote the further development of ARZIBs towards practical utility.

In this work, homogeneous Ni_0.33Co_0.67Se hollow nanoprisms were synthesized successfully in virtue of Kirkendall effect. It is the first time for bimetallic Ni-Co compounds Ni_0.33Co_0.67Se to be used in lithium-ion batteries (LIBs). Impressively, the Ni_0.33Co_0.67Se hollow nanoprisms show superior specific capacity (1, 575 mAh/g at the current density of 100 mA/g) and outstanding rate performance (850 mAh/g at 2, 000 mA/g) as anode material for LIBs. This work proves the potential of bimetallic chalcogenide compounds as high performance anode materials for LIBs.

K-ion battery (KIB) is a new-type energy storage device that possesses potential advantages of low-cost and abundant resource of potassium. To develop advanced electrode materials for accommodating the large size and high activity of potassium ion is of great interests. Herein, a segment-like antimony (Sb) nanorod encapsulated in hollow carbon tube electrode material (Sb@HCT) was prepared. Beneficial from the virtue of abundant nitrogen doping in carbon tube, one-dimensional and hollow structure advantages, Sb@HCT exhibits excellent potassium storage properties: in the case of potassium bis(fluorosulfonyl)imide (KFSI) electrolyte, Sb@HCT displays a reversible capacity of up to 453.4 mAh·g^-1 at a current density of 0.5 A·g^-1 and good rate performance (a capacity of 211.5 mAh·g^-1 could be achieved at an ultrahigh rate of 5 A·g^-1). Additionally, Sb@HCT demonstrates excellent long-cycle stability at a current density of 2 A·g^-1 over 120 cycles. Meanwhile, electrolyte optimization is an effective strategy for greatly improving electrochemical performance. Through ex-situ characterizations, we disclosed the potassiation of Sb anode is quite reversible and undergoes multistep processes, combining solid solution reaction and two-phase reaction.