Atomic-level structure engineering is an effective strategy to reduce mechanical degradation and boost ion transport kinetics for battery anodes. To address the electrode failure induced by large ionic radius of K+ ions, herein we synthesized Mn-doped ZnSe with modulated electronic structure for potassium ion batteries (PIBs). State-of-the-art analytical techniques and theoretical calculations were conducted to probe crystalline structure changes, ion/electron migration pathways, and micromechanical stresses evolution mechanisms. We demonstrate that the heterogeneous adjustment of the electronic structure can relieve the potassiumization-induced internal strain and improve the structural stability of battery anodes. Our work highlights the importance of the correlation between doping chemistry and mechanical stability, inspiring a pathway of structural engineering strategy toward a highly stable PIBs.

Hard carbon (HC) has attracted considerable attention in the application of sodium-ion battery (SIB) anodes, but the poor realistic capacity and low rate performance severely hinder their practical application. Herein we report a solvent mechanochemical protocol for the in situ fabrication of the HC-MXene/TiO 2 electrode by functionalizing MXene to improve the electrochemical performance of the batteries. MXene (Ti 3 C 2 T x ) with abundant oxygen-containing functional groups reacts with HC particles in the ball milling process to form a Ti−O−C covalent cross-linked HC-MXene composite, in which the edge of the MXene nanosheets is in situ oxidized by air to form TiO 2 nanorods, forming a regular 1D/2D MXene/TiO 2 heterojunction structure. Ti− O−C covalent bonding can protect the heterojunction structures from pulverization and detachment from the current collector during charge/discharge cycles due to sodium-ion intercalation/detachment, thus improving the stability of the electrode structure. Meanwhile, the MXene/TiO 2 heterojunction can form a 3D conductive network and provide more active sites. The resulting HC-MXene/TiO 2 electrode exhibits superior electrode capacity (660 mAh g −1 ), making it a promising anode material for SIBs. This simple and efficient method for preparing MXene/TiO 2 heterojunction-decorated HC provides a new perspective on the structural design of MXene and carbon material composites for SIBs. KEYWORDS: hard carbon, Ti 3 C 2 T x , TiO 2 nanorods, ball milling, sodium-ion batteries

The interface between carbon fibers and resin has a great effect on the mechanical properties of composites, and acts as a bridge for the transportation of load between fibers and resin. The traditional measurement method for interfacial shear strength (IFSS) relies mainly on single‐fiber fragmentation test, which is not suited for opaque composites. In this article, a new method for measuring the interfacial shear strength of opaque resin/carbon fibers was firstly put forward. We used mapping from energy dispersive X‐ray spectroscopy (EDS) which replaced the polarizing microscope to detect the breakpoints of samples after being stretched. We found that the value of IFSS for composites made by carbon fibers and epoxy resin detected by traditional method and new method was similar, which indicated single‐fiber fragmentation test based on mapping from EDS was accurate. The value of IFSS for composites made by carbon fibers and epoxy resin modified by carbon nanotubes was measured by mapping from EDS, which indicated the wide applicability in opaque composites. The single‐fiber fragmentation test based on mapping from EDS made the IFSS measurement of opaque composite become possible, which made a great progress compared with traditional method.

Owing to abundant polar groups and good lithiophilicity, protein materials regain interest for application in lithium metal batteries (LMBs). Current proteins with an αconformation for modifying lithium (Li) anodes possess typically poor mechanical properties, and there is therefore a significant need for advanced protein materials. Herein, a lysozyme-modified layer is coated onto the poly(vinylidene fluoride) electrospun mat for high mechanical strength and uniform Li-ion flux. The lysozyme membrane can regulate Li + deposition behavior due to complete β-sheet configuration, high lithiophilicity sulfhydryl groups, and columnar nanopores. As a result, the lysozyme-modified Li metal anode exhibits a high stability performance of Li−Li symmetric cells (2800 h) and Li-LiFePO 4 full cell (1450 cycles). Our strategy pushes the protein with β-sheet configuration toward the applications of next-generation LMBs.

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