Silicon‐based anodes with high theoretical capacity have intriguing potential applications for next‐generation high‐energy lithium‐ion batteries, but suffer from huge volumetric change that causes pulverization of electrodes. Rational design and construction of effective electrode structures combined with versatile binders remain a significant challenge. Here, a unique natural binder of konjac glucomannan (KGM) is developed and an amorphous protective layer of SiO2 is fabricated on the surface of Si nanoparticles (Si@SiO2) to enhance the adhesion. Benefiting from a plethora of hydroxyl groups, the KGM binder with inherently high adhesion and superior mechanical properties provides abundant contact sites to active materials. Molecular mechanics simulations and experimental results demonstrate that the enhanced adhesion between KGM and Si@SiO2 can bond the particles tightly to form a robust electrode. In addition to bridging KGM molecules, the SiO2‐functionalized surface may serve as a buffer layer to alleviate the stresses of Si nanoparticles resulting from the volume change. The as‐fabricated KGM/Si@SiO2 electrode exhibits outstanding structural stability upon long‐term cycles. A highly reversible capacity of 1278 mAh g−1 can be achieved over 1000 cycles at a current density of 2 A g−1, and the capacity decay is as small as 0.056% per cycle.

Safety issues in lithium‐ion batteries (LIBs) have aroused great interest owing to their wide applications, from miniaturized devices to large‐scale storage plants. Separators are a vital component to ensure the safety of LIBs; they prevent direct electric contact between the cathode and anode while allowing ion transport. In this study, the first design is reported for a thermoregulating separator that responds to heat stimuli. The separator with a phase‐change material (PCM) of paraffin wax encapsulated in hollow polyacrylonitrile nanofibers renders a wide range of enthalpy (0–135.3 J g−1), capable of alleviating the internal temperature rise of LIBs in a timely manner. Under abuse conditions, the generated heat in batteries stimulates the melting of the encapsulated PCM, which absorbs large amounts of heat without creating a significant rise in temperature. Experimental simulation of the inner short‐circuit in prototype pouch cells through nail penetration demonstrates that the PCM‐based separator can effectively suppress the temperature rise due to cell failure. Meanwhile, a cell penetrated by a nail promptly cools down to room temperature within 35 s, benefiting from the latent heat‐storage of the unique PCM separator. The present design of separators featuring latent heat‐storage provides effective strategies for overheat protection and enhanced safety of LIBs.

Ionogels are considered promising electrolytes for safe lithium‐ion batteries (LIBs) because of their low flammability, good thermal stability, and wide electrochemical stability window. Conventional ionic liquid‐based ionogels, however, face two main challenges; poor mechanical property and low Li‐ion transfer number. In this work, a novel solvate ionogel electrolyte (SIGE) based on an organic–inorganic double network (DN) is designed and fabricated through nonhydrolytic sol–gel reaction and in situ polymerization processes. The unprecedented SIGE possesses high toughness (bearing the deformation under the pressure of 80 MPa without damage), high Li‐ion transfer number of 0.43, and excellent Li‐metal compatibility. As expected, the LiFePO4/Li cell using the newly developed SIGE delivers a high capacity retention of 95.2% over 500 cycles, and the average Coulombic efficiency is as high as 99.8%. Moreover, the Ni‐rich LiNi0.8Co0.1Mn0.1O2 (NCM811)/Li cell based on the modified SIGE achieves a high Coulombic efficiency of 99.4%, which outperforms previous solid/quasi‐solid‐state NCM811‐based LIBs. Interestingly, the SIGE‐based pouch cells are workable under extreme conditions (e.g., severely deforming or clipping into segments). In terms of those unusual features, the as‐obtained SIGE holds great promise for next‐generation flexible and safe energy‐storage devices.

With the rapid development of lithium‐ion batteries (LIBs), safety problems are the great obstacles that restrict large‐scale applications of LIBs, especially for the high‐energy‐density electric vehicle industry. Developing component materials (e.g., cathode, anode, electrolyte, and separator) with high thermal stability and intrinsic safety is the ultimate solution to improve the safety of LIBs. Separators are crucial components that do not directly participate in electrochemical reactions during charging/discharging processes, but play a vital role in determining the electrochemical performance and safety of LIBs. In this review, the recent advances on traditional separators modified with ceramic materials and multifunctional separators ranging from the prevention of the thermal runaway to the flame retardant are summarized. The component–structure–performance relationship of separators and their effect on the comprehensive performance of LIBs are discussed in detail. Furthermore, the research challenges and future directions toward the advancement in separators for high‐safety LIBs are also proposed.

No abstract