The reasonable design of electrode materials for rechargeable batteries plays an important role in promoting the development of renewable energy technology. With the in-depth understanding of the mechanisms underlying electrode reactions and the rapid development of advanced technology, the performance of batteries has significantly been optimized through the introduction of defect engineering on electrode materials. A large number of coordination unsaturated sites can be exposed by defect construction in electrode materials, which play a crucial role in electrochemical reactions. Herein, recent advances regarding defect engineering in electrode materials for rechargeable batteries are systematically summarized, with a special focus on the application of metal-ion batteries, lithium-sulfur batteries, and metal-air batteries. The defects can not only effectively promote ion diffusion and charge transfer but also provide more storage/adsorption/active sites for guest ions and intermediate species, thus improving the performance of batteries. Moreover, the existing challenges and future development prospects are forecast, and the electrode materials are further optimized through defect engineering to promote the development of the battery industry.

Defect Engineering on Electrode Materials for Rechargeable Batteries.

The tremendous improvement in performance and cost of lithium-ion batteries (LIBs) have made them the technology of choice for electrical energy storage. While established battery chemistries and cell architectures for Li-ion batteries achieve good power and energy density, LIBs are unlikely to meet all the performance, cost, and scaling targets required for energy storage, in particular, in large-scale applications such as electrified transportation and grids. The demand to further reduce cost and/or increase energy density, as well as the growing concern related to natural resource needs for Li-ion have accelerated the investigation of so-called "beyond Li-ion" technologies. In this review, we will discuss the recent achievements, challenges, and opportunities of four important "beyond Li-ion" technologies: Na-ion batteries, K-ion batteries, all-solid-state batteries, and multivalent batteries. The fundamental science behind the challenges, and potential solutions toward the goals of a low-cost and/or high-energy-density future, are discussed in detail for each technology. While it is unlikely that any given new technology will fully replace Li-ion in the near future, "beyond Li-ion" technologies should be thought of as opportunities for energy storage to grow into mid/large-scale applications.

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Promises and challenges of next-generation "beyond Li-ion" batteries for electric vehicles and grid decarbonization

Rechargeable aqueous metal-ion batteries are very promising as alternative energy storage devices during the post-lithium-ion era because of their green and safe inherent features. Among the different aqueous metal-ion batteries, aqueous zinc-ion batteries (ZIBs) have recently been studied extensively due to their unique and outstanding benefits that hold promise for large-scale power storage systems. However, zinc anode problems in ZIBs, such as zinc dendrites and side reactions, severely shorten the ZIB's cycle lifetime, thus restricting their practical application. Here, we sum up in detail the recent progress on general strategies to suppress zinc dendrites and zinc anode side reactions based on advanced materials and structure design, including the modification of the planar zinc electrode surface layer, internal structural optimization of the zinc bulk electrode, modification of the electrolyte and construction of the multifunctional separator. The various functional materials, structures and battery efficiencies are discussed. Finally, the challenges for ZIBs are identified in the production of functional zinc anodes.

Challenges in the material and structural design of zinc anode towards high-performance aqueous zinc-ion batteries

Metallic zinc is a promising anode candidate of aqueous zinc-ion batteries owing to its high theoretical capacity and low redox potential. However, Zn anodes usually suffer from dendrite and side reactions, which will degrade their cycle stability and reversibility. Herein, we developed an in situ spontaneously reducing/assembling strategy to assemble a ultrathin and uniform MXene layer on the surface of Zn anodes. The MXene layer endows the Zn anode with a lower Zn nucleation energy barrier and a more uniformly distributed electric field through the favorable charge redistribution effect in comparison with pure Zn. Therefore, MXene-integrated Zn anode exhibits obviously low voltage hysteresis and excellent cycling stability with dendrite-free behaviors, ensuring the high capacity retention and low polarization potential in zinc-ion batteries.

Direct Self‐Assembly of MXene on Zn Anodes for Dendrite‐Free Aqueous Zinc‐Ion Batteries

The development of low-cost and high-safety zinc-ion batteries (ZIBs) has been extensively discussed and reviewed in recent years, but the work on the comprehensive discussion and perspectives in developing zinc-ion electrolytes is still relatively lacking. Faced with critical challenges and bottlenecks practically, the viability of ZIBs critically depends on the development of suitable electrolytes and their practical considerations. In this review, a systematic summary with regard to the basic characteristics of zinc-ion electrolytes facing different issues from optimization strategies to the fundamental science of electrolyte/electrode interfaces (EEIs), particularly in the feasible modifications and advanced characterizations of EEIs, has been put forward. Due to the lack of consideration of the practical issues in major academic studies, we have particularly highlighted aspects that mainly focus on the choice of the electrolyte system, dosage of liquid and fluid electrolytes, status of gel and all-solid electrolytes, together with other concerns related to the electrolytes. The final section proposes significant perspectives to guide and promote the development of zinc-ion electrolytes.

Fundamentals and perspectives in developing zinc-ion battery electrolytes: a comprehensive review

Aqueous zinc-ion batteries have rapidly developed recently as promising energy storage devices in large-scale energy storage systems owing to their low cost and high safety. Research on suppressing zinc dendrite growth has meanwhile attracted widespread attention to improve the lifespan and reversibility of batteries. Herein, design methods for dendrite-free zinc anodes and their internal mechanisms are reviewed from the perspective of optimizing the host-zinc interface and the zinc-electrolyte interface. Furthermore, a design strategy is proposed to homogenize zinc deposition by regulating the interfacial electric field and ion distribution during zinc nucleation and growth. This Minireview can offer potential directions for the rational design of dendrite-free zinc anodes employed in aqueous zinc-ion batteries.

Interfacial design of dendrite‐free zinc anodes for aqueous zinc‐ion batteries

Advancements and Challenges in Potassium Ion Batteries: A Comprehensive Review

Vacancy engineering is a promising approach for optimizing the energy storage performance of transition metal dichalcogenides (TMDs) due to the unique properties of vacancies in manipulating the el...

Anion Vacancies Regulating Endows MoSSe with Fast and Stable Potassium Ion Storage

Organic electrode materials offer a new opportunity to develop high energy/power density, low-cost, environmentally benign sodium ion batteries (SIBs). For many years this category of materials has not been considered as a potential electrode candidate for SIBs mainly because excessive research focused on inorganic materials due to their successful commercialization in the proven lithium ion battery (LIB) technologies. However, recently, many promising advancements have been made in the field of organic cathode and anode materials for SIB applications. This review for the first time consolidates and provides insights into the different sodium storage mechanisms observed in various categories of organic electrode materials. We believe that the fundamental understanding of the redox mechanisms that govern the electrochemical performances of SIBs is necessary to design new materials/electrodes and is beneficial for enhancing the existing properties of investigated compounds.

Yougen Tang

Papers

Interfacial design of dendrite‐free zinc anodes for aqueous zinc‐ion batteries

Advancements and Challenges in Potassium Ion Batteries: A Comprehensive Review

Anion Vacancies Regulating Endows MoSSe with Fast and Stable Potassium Ion Storage

Understanding the sodium storage mechanisms of organic electrodes in sodium ion batteries: issues and solutions

Sn layer decorated copper mesh with superior lithiophilicity for stable lithium metal anode