Surface chemistry of MXenes is of significant interest due to its potential to control their final optoelectronic and physicochemical properties, and address the oxidation and dispersion stabilities of MXenes. Surface chemistry of MXenes can be manipulated by either MXene synthesis via chemical etching or post surface functionalization method. Although numerous reviews have explored MXene synthesis methods, there has been a lack of focus on post surface functionalization. This review aims to fill this gap by summarizing recent advancements in the MXene surface functionalization chemistry, and elucidating mechanisms, properties, and future perspectives of functionalized MXenes. We discuss organic ligand molecules, such as organic salts, catechols, phosphonates, carboxylates, and silanes, which can be employed to surface-functionalize MXene through covalent or non-covalent bond interaction. This comprehensive review offers valuable insights for scientists and engineers in utilizing functionalized MXenes across diverse applications, including EMI shielding, energy storage, electronics, optoelectronics, and sensors.

Sulfide solid state electrolyte (SSE) possesses high ionic conductivity and great processability but suffers from narrow electrochemical window. Conversion sulfide cathode FeS2 has higher specific capacity and moderate redox potential, making it appropriate toward sulfide SSE. However, the complex reaction pathway and capacity fading mechanism in FeS2 are rarely studied, especially in all-solid-state lithium battery (ASSLB). Herein, argyrodite sulfide SSE is paired with FeS2 to investigate the electrochemical reaction pathways and the capacity fade mechanism. Instead of single conversion reaction, an anionic redox driven reaction of FeS2 is revealed. The oxidization of Li2S vanishes and large quantity of inactive Li2S accumulates to cause the interfacial deterioration, along with the stress concentration during cycling, which leads to the rapid capacity fade of FeS2. Finally, a simple strategy of slurry-coated composite electrode with highly conductive network is proposed to direct the uniform deposition of Li2S and alleviate the stress concentration.

Owing to the lightweight, flexibility, and molecular diversity, organic photothermal materials are considered promising solar absorbent materials for water-evaporating purification. Herein, we utilize the blend of two organic conjugated photothermal materials, PM6 and Y6, with broadband solar absorption from 350 to 1000 nm and high-efficiency photothermal properties to fabricate a Janus water evaporator on cellulose paper. Similar to the asymmetric wetting behavior on the lotus leaf, the evaporator shows efficient water adhesion on the bottom surface and water repellency on the top surface for a desirable self-floating capability and salt resistance. With a mass of only 0.5 mg per 3.14 cm2, the PM6:Y6 blend-based water evaporator achieves 88.9% of solar thermal conversion efficiency (η) and 1.52 kg m−2 h−1 of solar water evaporation rate (m) under 1.0 kW m−2 solar irradiation. These properties are almost the best performance among purely organic water evaporators especially with such a premise of material saving. The concentrations of primary ions are significantly decreased by 4–6 orders after desalination, accompanied by excellent performance for wastewater treatment. This evaporator realizes a m of 1.21 kg m−2 h−1, a η of 75.7%, and a voltage of 61 mV under one sun irradiation by assembling with a thermoelectric equipment. This study demonstrates that the blending of PM6 and Y6 achieves photothermal synergism, which improves the photothermal property and water evaporation rate, providing a valuable prospect for their application in water purification and thermoelectric power generation.

To achieve next-generation lithium metal batteries (LMBs) with desirable specific energy and reliability, the electrolyte shown simultaneously high reductive stability toward lithium metal anode and oxidative stability toward high-voltage cathode is of great importance. Here, we report for the first time that high-concentration lithium bis(fluorosulfonyl)imide (LiFSI) initiates ring-opening polymerization of 1,3-dioxolane in presence of ethylene carbonate and ethylmethyl carbonate to produce in-situ a novel polymeric concentrated quasi-solid electrolyte (poly-CQSE). The unique poly-CQSE with 10 M LiFSI forms a mixed-lithiophobic-conductive LiF-Li3N solid electrolyte interphase on lithium metal anode, and a F-rich conformal cathode electrolyte interphase on LiNi0.5Co0.2Mn0.3O2 (NCM523) cathode simultaneously. As a result, the poly-CQSE not only enables stable Li plating/stripping of metallic Li anode at a sound Coulombic efficiency of 95.3% without dendrite growth, but also enables a stable cycling of the Li||NCM523 quasi-solid-state LMB at a capacity retention of 94% over 100 cycles.

Defects in CH3NH3PbI3 perovskites, oxygen species in the air, and local charges play a significant role in the long-term stability of perovskites. However, the interplay of these factors are complex and their role in the degradation of perovskites at the atomistic level is not well understood. By using density functional theory calculations and chemical bonding analysis, we study the effect of oxygen and local charges on the degradation of perovskites. We find that the easier formation of I vacancies upon oxygen and the accelerated degradation of CH3NH3PbI3 by excess electrons via the formation of peroxide species. The creation of peroxide disintegrates the lattice of perovskites on the surfaces and possibly induces a cascade of degradation reactions that eventually destruct the perovskite lattices. We further demonstrate that the addition of holes are beneficial to prevent the formation of the peroxide, therefore can potentially improve the stability of the perovskites.

Realizing environmental compatibility and high power conversion efficiency (PCE) are crucial in the research of organic photovoltaics towards practical application. Applying environmentally friendly bio-materials into the modification of cathode interlayer (CIL) is a feasible approach to move towards both targets. In this research, three edible bio-acids, ursolic acid, citric acid, and malic acid, are employed to modify the PDIN CIL of the organic solar cells (OSCs) with non-fullerene acceptors. Among these edible bio-acid modifiers, ursolic acid shows its excellent performance in improving interfacial contact and suppressing charge recombination. It helps to obtain a good interfacial contact and facilitates the electron extraction. As a result, the photovoltaic performance is significantly improved. The average PCE are increased from 17.58% of the control devices to 18.35% of the PDIN + Ursolic Acid based devices, with a maximum PCE of 18.54%. It is the champion efficiency among the reported applications of bio-derived materials for the CILs. This study demonstrates the successful application of edible bio-acid, which offers an effective and green approach for the CIL modification to realize highly efficient OSCs.

As a group of emerging liquid-like thermoelectric materials for waste heat recovery into useful energy, di-chalcogenides Cu2(S, Se, Te) have been considered as superionic thermoelectric materials. Due to their highly disordered degree of Cu-ion in the crystal lattice, Cu2(S, Se, Te) compounds can exhibit ultralow thermal conductivity, and in the meantime, their rigid sublattice can decently maintain the electrical performance, making them distinct from other state-of-the-art thermoelectric materials. This review summarizes the well-designed strategies to realize the impressive performance in thermoelectric materials and their modules by linking the adopted approaches such as defect engineering, interfaces, nano-porous inclusions, thin films, dislocations, nano-inclusions, and polycrystalline bulks etc., with the moderate design of the device. Some recent reports are selected to outline the fundamentals, underlined challenges, outlooks, and future development of Cu2(S, Se, Te) liquid-like thermoelectric materials. We expect that this review covers the needs of future researchers in choosing some potential materials to explore thermoelectricity and other efficient energy conversion technologies.

Rechargeable zinc-air batteries (ZABs) are cost-effective energy storage devices and display high-energy density. To realize high round-trip energy efficiency, it is critical to develop durable bi-functional air electrodes, presenting high catalytic activity towards oxygen evolution/reduction reactions together. Herein, we report a nanocomposite based on ternary CoNiFe-layered double hydroxides (LDH) and cobalt coordinated and N-doped porous carbon (Co-N-C) network, obtained by the in-situ growth of LDH over the surface of ZIF-67-derived 3D porous network. Co-N-C network contributes to the oxygen reduction reaction activity, while CoNiFe-LDH imparts to the oxygen evolution reaction activity. The rich active sites and enhanced electronic and mass transport properties stemmed from their unique architecture, culminated into outstanding bi-functional catalytic activity towards oxygen evolution/reduction in alkaline media. In ZABs, it displays a high peak power density of 228 mW cm−2 and a low voltage gap of 0.77 V over an ultra-long lifespan of 950 h.

Sodium-ion battery (SIB) is considered as a revolutionary technology toward large-scale energy storage applications. Developing cost-effective cathode material as well as economical synthesis procedure is a key challenge for its commercialization. Herein, we develop a facile and economic strategy to simultaneously remove rust from the surface of carbon steel and achieve porous and hollow spherical Na4Fe3(PO4)2P2O7/C (HS-NFPP/C). Benefiting from the desirable structure that fastens the electronic/ionic transportation and effectively accommodates the volume expansion/contraction during discharge/charge process, the as-prepared cathode exhibits outstanding rate capability and ultralong cycle life. An extraordinarily high-power density of 32.3 kW kg−1 with an ultrahigh capacity retention of 89.7% after 10 000 cycles are achieved. More significantly, the 3 Ah HC||HS-NFPP/C full battery manifests impressive cycling stability. Therefore, this work provides an economical and sustainable approach for the massive production of high-performance Na4Fe3(PO4)2P2O7 cathode, which can be potentially commercialized toward SIB applications.

Nowadays, LiCoO2 has dominated the cathode technology of lithium-ion batteries (LIBs) for 3C digital devices, but the sluggish electrochemical kinetics and severe structure destruction limit its further application under extreme temperatures. Herein, we design a synergetic strategy including La, Mg co-doping and LiAlO2@Al2O3 surface coating. Typically, the La3+ increases the interlayer distance and significantly enhances the ionic conductivity, the Mg2+ improves electronic conductivity, and the LiAlO2@Al2O3 coating layer improves the interfacial charge transfer and suppresses the polarization. The co-modified LiCoO2 (CM-LCO) shows excellent temperature adaptability with remarkable electrochemical performance in a wide temperature range (−40–70°C). Remarkably, the CM-LCO also exhibits excellent cycle stability and high-rate performance at extreme temperatures. The synergistic effects of this co-modification strategy are demonstrated by investigating the electrochemical reaction kinetics and structure evolution of CM-LCO. This work proposes a promising strategy for the application of the high-voltage LCO in a wide temperature range.

Layered vanadium oxides are promising cathode materials for zinc-ion batteries (ZIBs) owing to their high capacity, but the sluggish electron/ion migration kinetics and structural collapse/dissolution severely limit their Zn2+-storage performance. Herein, poly(3,4-ethylenedioxythiophene) coated and Mn2+-intercalated vanadium oxides with rich oxygen vacancies (MnVOH@PEDOT) are prepared as the cathodes for ZIBs. The PEDOT coating, synergistic with oxygen vacancies, tailors the electron conductivity, and the Mn2+-intercalation enlarges the interlayer spacing for rapid Zn2+-ions diffusion. In addition, the pre-intercalated Mn2+-ions act as “pillars” to stabilize the structure, and the PEDOT coating prevents the direct contact of vanadium oxides with electrolyte to inhibit its dissolution during cycling. Thus, the MnVOH@PEDOT cathode exhibits superior discharge capacity, favorable rate capability (336.0 mAh g−1 at 8 A g−1), and satisfying cyclic durability (84.8% capacity retention over 2000 cycles). This work offers a facile and synergistic design strategy for achieving favorable cathodes for ZIBs.

It is a long-standing issue that the sluggish polysulfide conversion and adverse shuttling effects impede the development of lithium-sulfur (Li-S) batteries with high energy density and cycling stability, which necessitate the exploration of new electrocatalysts to facilitate the practical applications of Li-S batteries. Herein, a single-phase high-entropy stabilized oxide (Ni0.2Co0.2Cu0.2Mg0.2Zn0.2)O (HEO850) is successfully prepared through a novel low-temperature annealing strategy from a self-sacrificing metal–organic frameworks (MOFs) template and then integrated into the sulfur host, where it functions as both the catalytic converter and chemical inhibitor towards the shuttle species. Furthermore, the synergistic contribution of randomly dispersed metal elements and the exposure of affluent active sites enable the chemical encapsulation of soluble polysulfides and accelerate conversion kinetics. The HEO850/S/KB cathode (KB: ketjen black; sulfur content: 70 wt.%) delivers a substantially higher initial specific discharge capacity of ~1244 mAh g−1 in comparison to MEO/S/KB (MEO: medium entropy oxide; ~980 mAh g−1), LEO/S/KB (LEO: low entropy oxide; ~908 mAh g−1), and routine S/KB cathodes (~966 mAh g−1), which is well retained at ~784 mAh g−1 after 800 cycles at 0.5 C with a low capacity decay rate of ~0.043% per cycle. Moreover, when the HEO850/S/KB cathode is processed with a high areal sulfur loading (~4.4 mg cm−2), the resulting Li-S battery also performs well, with a high initial specific capacity of ~1044 mAh g−1 at 0.1 C and 85% capacity retention after 100 cycles. This study highlights the potential application of HEOs in enhancing the performance of Li-S batteries and provides a novel strategy in synthesizing the HEOs at a relatively low annealing temperature for various energy conversion and storage applications.

Pt-Ir catalysts have been widely applied in unitized regenerative fuel cells due to their great activity for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). However, the application of noble metals is seriously hindered by their high cost and low abundance. To reduce the noble metals loading and catalyst cost, the atomic layer deposition is applied to selectively surface anchoring of Ir single atoms (SA) on Pt nanoparticles (NP). With the formation of SA-NP composite structure, the IrSA-PtNP catalyst exhibits significantly improved performance, achieving 2.0- and 90-times mass activity by comparison with the benchmark Pt/C catalyst for the ORR and OER, respectively. Density functional theory calculations indicate that the SA-NP cooperation synergy endows the IrSA-PtNP catalyst to surpass the bifunctional catalytic activity limit of Pt-Ir NPs. This work provides a novel strategy for the construction of high-performing dual catalyst through designing the single atom anchoring on NPs.

Developing cost–benefit and high-performance non-noble metal oxygen reduction reaction (ORR) electrocatalysts is highly imperative for wide applications of renewable energy conversion devices. Herein, a one stone two birds phosphorization strategy has been proposed to synthesize hollow structured Cu/Cu3P heterogeneous nanoparticles supported on N, P co-doped carbon (Cu/Cu3P@NP-Cs). The optimized Cu/Cu3P@NP-C-900 features high ORR performance under both alkaline and acidic conditions. Moreover, the Cu/Cu3P@NP-C-900-drivened Zn-air battery exhibits a substantially higher power density output (148.2 mW cm−2) and stronger charge–discharge stability (300 h, 1805 cycles) than those of Pt/C-equipped counterpart. The cross-interface electron transfer from Cu3P to Cu effectively regulates the d-band center of Cu/Cu3P, thereby leading to the balanced adsorption/desorption energy of oxygen species. Meanwhile, the hollow structure maximizes the exposure of accessible active centers, resulting in much accelerated ORR kinetics. This work proposes an innovative insight for developing hollow hetero-structured catalysts to improve ORR performance.

For a “Carbon Neutrality” society, electrochemical energy storage and conversion (EESC) devices are urgently needed to facilitate the smooth utilization of renewable and sustainable energy where the electrode materials and catalysts play a decisive role. However, the efficiency of the current trial-and-error research paradigm largely lags behind the imminent demands of EESC requiring increasingly improved performance. The emerged machine learning (ML), a subfield of artificial intelligence, is capable of evaluating and analyzing big data for hidden rules. In this regard, the relationships between the structure and performance of the key materials can be more efficiently revealed, which fundamentally revolutionizes the material research manner of the current EESC devices. In this review, the typical ML algorithms utilized in EESC development are first introduced. Then, focused attention has been paid to multiple aspects of applying ML to reshape the materials research for EESC. In addition to highlighting the emerging prospect, the challenges which are still hindering the further development of this emerging field are also discussed.

The cover image shows the heat charge/discharge process of layered Sr3Fe2O7. The left side of the picture presents daytime, which means Sr3Fe2O7 absorbs solar energy and releases O2 to store chemical energy, while the right side of the image presents night, which means Sr3Fe2O7 reacts with O2 to release stored heat and generate electricity.

A smart textile that could harvest mechanical-energy for photo-thermal energy utilization facilitates the development of a flexible self-heating wearable device. This study presents novel triboelectric materials with a dynamic-bond-cross-linking azobenzene-based polymer (PAzo-M) with diverse metal ions. The flexible nylon fabric coated with PAzo-M (NF@PAzo-M) serves as a friction layer of the photothermal triboelectric nanogenerator (PT-TENG) to harvest human mechanical energy. The prepared PT-TENG could exhibit a maximum open-circuit voltage of up to 188.8 V with excellent electron loss capability because of its minimum vertical electron affinity of internal ion. And it can harvest mechanical energy from human motion (0.5–1 Hz) to drive the self-powering irradiation of ultraviolet light or visible light, leading to the reversible isomerization of NF@PAzo-M. The NF@PAzo-M textile cyclically utilizes photo-thermal energy for self-heating. These results suggest new opportunities to harvest human mechanical energy for self-powering multifunctional wearable devices for functions.

The problematic Zn dendrite for Zn anodes remains a great challenge. Constructing an artificial Cu-Zn alloy layer is one of the most potential solutions. However, it is still challenging to prepare an ideal Cu-Zn alloy layer with good morphology and controllable thickness. Herein, a special plasma-based method of active screen plasma (ASP) is first reported to create a hexagonal close-packed CuZn5 alloy layer with controllable morphology and thickness. Meanwhile, a “vaporization-redeposition” mode is proposed to illustrate the alloying process. Based upon system analysis, the CuZn5 layer with good uniformity and appropriate thickness can regulate the behavior of Zn-ion at electrode/electrolyte interface. The former homogenizes the electric field distribution, while the latter enhances de-solvation ability of Zn-ion, facilitating Zn-ion diffusion. Consequently, the CuZn5-coated Zn anodes display lower polarization potential and longer cycling life. Such CuZn5-coated Zn anodes enable an outstanding cycle stability for Zn-based devices, and the pouch devices also deliver practicality.

Lithium-ion batteries (LIBs) have been dominating the markets of electric vehicles and grid energy storage. Accurate monitoring of battery health status has been one of the most critical challenges of the battery industry. Machine learning (ML) has been widely applied to battery health estimation as well as prediction. Here, by investigating the specific features and targets, we comprehensively discuss task-oriented ML implementation in various application scenarios in the field of battery health. This review explores the tasks assisted by ML based on multi-level cell degradation. We highlight opportunities and significance of considering the potential feature–target pair during the ML model training to identify more health information about LIBs as well as shed light into designing tasks for new application scenarios.

Sulfide solid electrolyte (SSE)-based all-solid-state Li batteries (ASSLBs) can overcome the problems of low energy density and safety concern of current Li-ion batteries. However, the practical application of SSE-based ASSLBs is suffered from several problems, especially interfacial issues between Li metal anode (LMA) and SSEs. Therefore, in this study, the problems of the LMA–SSE interface and their corresponding solutions are reviewed. First, the interfacial problems are summarized, namely the side reactions of SSEs, the Li dendrite growth, and poor contact between the electrode and electrolyte. Second, the available strategies to improve the robustness of the interface are discussed, including the protection of the LMA, substitution of the LMA, and modification of SSEs. Third, the characterization methods used to analyze the morphological and compositional evolution of the interface during cycling are introduced. Finally, the limitations and future research directions are proposed.