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The in situ introduced oxygen vacancies deliver dual functionality for realizing the high-voltage operation of NaCrO2–x (charged up to 3.8 V) by facilitating reversible TM migration and improving the rate capability by expediting ion diffusivity.

Because of their high ionic conductivity, utilizing gel polymer electrolytes (GPEs) is thought to be an effective way to accomplish high-energy-density batteries. Nevertheless, most GPEs have poor adaptability to Ni-rich cathodes to alleviate the problem of inevitable rapid capacity decay during cycling. Therefore, to match LiNi

It is crucial for metal-air batteries and fuel cells to design non-precious-metal catalysts instead of platinum-based materials to boost the sluggish oxygen reduction reaction (ORR). Herein, Co

Compared with commercial lithium batteries with liquid electrolytes, all‐solid‐state lithium batteries (ASSLBs) possess the advantages of higher safety, better electrochemical stability, higher energy density, and longer cycle life; therefore, ASSLBs have been identified as promising candidates for next‐generation safe and stable high‐energy‐storage devices. The design and fabrication of solid‐state electrolytes (SSEs) are vital for the future commercialization of ASSLBs. Among various SSEs, solid polymer composite electrolytes (SPCEs) consisting of inorganic nanofillers and polymer matrix have shown great application prospects in the practice of ASSLBs. The incorporation of inorganic nanofillers into the polymer matrix has been considered as a crucial method to achieve high ionic conductivity for SPCE. In this review, the mechanisms of Li+ transport variation caused by incorporating inorganic nanofillers into the polymer matrix are discussed in detail. On the basis of the recent progress, the respective contributions of polymer chains, passive ceramic nanofillers, and active ceramic nanofillers in affecting the Li+ transport process of SPCE are reviewed systematically. The inherent relationship between the morphological characteristics of inorganic nanofillers and the ionic conductivity of the resultant SPCE is discussed. Finally, the challenges and future perspectives for developing high‐performance SPCE are put forward. This review aims to provide possible strategies for the further improvement of ionic conductivity in inorganic nanoscale filler‐reinforced SPCE and highlight their inspiration for future research directions.

Mn-based layered oxides are very attractive as cathodes for potassium-ion batteries (PIBs) due to their low-cost and environmentally friendly precursors. Their transfer to practical application, however, is inhibited by some issues including consecutive phase transitions, sluggish K+ deintercalation/intercalation, and serious capacity loss. Herein, Mg-Ni co-substituted K1/2Mn5/6Mg1/12Ni1/12O2 is designed as a promising cathode material for PIBs, with suppressed phase transitions that occurred in K1/2MnO2 and improved K+ storage performance. Part of Mg2+ and Ni2+ occupies the K+ layer, playing the role of a "nailed pillar", which restrains metal oxide layer gliding during the K+ (de)intercalation. The "Mg-Ni pinning effect" not only suppresses the phase transitions but also reduces the cell volume variation, leading to the improved cycle performance. Moreover, K1/2Mn5/6Mg1/12Ni1/12O2 has low activation barrier energy for K+ diffusion and high electron conductivity as demonstrated by first-principles calculations, resulting in better rate capability. In addition, K1/2Mn5/6Mg1/12Ni1/12O2 also delivers a higher reversible capacity owing to the participation of the Ni element in electrochemical reactions and the pseudocapacitive contribution. This study provides a basic understanding of structural evolution in layered Mn-based oxides and broadens the strategic design of cathode materials for PIBs.

O3-type NaCrO2 is attracting increasing attention as potential cathode material for sodium-ion batteries (SIBs). Bare NaCrO2 is usually synthesized by a solid-state reaction and suffers from serious capacity decay and poor power capability. Modification by coating is an effective method to improve the electrochemical properties, but it inevitably reduces the energy density. To avoid the decrease of energy density and optimize the electrochemical performance, a specific route, i.e., a freeze-drying-assisted sol-gel method, has been adopted to synthesize bare NaCrO2 in this work. Three-phase coexistence during charging is confirmed for the first time, which contributes to delaying the disappearance of the O3 phase and then improving the structural reversibility, resulting in superior cycle stability (∼50% capacity retention after 3000 cycles at 5C). Meanwhile, as-synthesized NaCrO2 delivers an outstanding rate capability (82.1 mAh g-1 at 50C), which is attributed to the fast Na+ diffusivity and high electronic conductivity proved by density functional theory (DFT) calculations. It is worth mentioning that NaCrO2 also exhibits excellent electrochemical properties when used as a cathode for potassium-ion batteries (PIBs). This work provides new perspectives on the structural evolution of NaCrO2, and the results are expected to contribute to the development of SIBs and PIBs.

Practical application of lithium metal anodes in high-energy rechargeable batteries is impeded by the issue of Li dendrite growth. Herein, an exceptional hydrophobic MAF-6 material is utilized to modify polypropylene (PP) separator to yield a superorganophilic MAF-6/PP composite separator. Owing to a combination of superorganophilicity with three-dimensional ordered porosity, the MAF-6/PP achieves a Li ion transference number of 0.78. Homogeneous and dense Li plating behaviors are present in cells with MAF-6/PP which can afford uniform Li ion flux. The MAF-6/PP enables Li|Cu cells to run steadily for over 350 cycles at 0.5 mA cm−2-1 mAh cm−2 with an average coulombic efficiency (CE) of 98.8%, symmetric Li|Li cells to work stably for 2200 h without short-circuit at 0.5 mA cm−2-1 mAh cm−2, and Li|LiFePO4 cells to retain a reversible capacity of 102.4 mAh g−1 after 1500 cycles at 1C with a capacity retention of 73.2% and a CE of 99.9%.

Aqueous batteries that use metal anodes exhibit maximum anodic capacity, whereas the energy density is still unsatisfactory partially due to the high redox potential of the metal anode. Current metal anodes are plagued by the dilemma that the redox potential of Zn is not low enough, whereas Al, Mg, and others with excessively low redox potential cannot work properly in aqueous electrolytes. Mn metal with a suitably low redox potential is a promising candidate, which was rarely explored before. Here, we report a rechargeable aqueous Mn-metal battery enabled by a well-designed electrolyte and robust inorganic-organic interfaces. The inorganic Sn-based interface with a bottom-up microstructure was constructed to preliminarily suppress water decomposition. With this bubble-free interface, the organic interface can be formed via an esterification reaction of sucrose triggered by acyl chloride in the electrolyte, generating a dense physical shield that isolates water while permitting Mn

All-solid-state lithium batteries (ASSLB) are promising candidates for next-generation energy storage devices. Nevertheless, the large-scale commercial application of high energy density ASSLB with the polymer electrolyte still faces challenges. In this study, a thin solid polymer composite electrolyte (SPCE) is prepared through a facile and cost-effective strategy with an infiltration of thermoplastic polyurethane (TPU), lithium salt (LiTFSI or LiFSI), and halloysite nanotubes (HNTs) in a porous framework of polyethylene separator (PE) (TPU–HNTs–LiTFSI–PE or TPU–HNTs–LiFSI–PE). The composition, electrochemical performance, and especially the effect of anions (TFSI− and FSI−) on cycling performance are investigated. The results reveal that the flexible TPU–HNTs–LiTFSI–PE and TPU–HNTs–LiFSI–PE with a thickness of 34 μm exhibit wide electrochemical windows of 4.9 and 5.1 V (vs. Li+/Li) at 60 ℃, respectively. Reduction in FSI− tends to form more LiF and sulfur compounds at the interface between TPU–HNTs–LiFSI–PE and Li metal anode, thus enhancing the interfacial stability. As a result, cell composed of TPU–HNTs–LiFSI–PE exhibits a smaller increase in interfacial resistance of solid electrolyte interphase (SEI) with a distinct decrease in charge-transfer resistance during cycling. Li|Li symmetric cell with TPU–HNTs–LiFSI–PE could keep its stable overpotential profile for nearly 1300 h with a low hysteresis of approximately 39 mV at a current density of 0.1 mA cm−2, while a sudden voltage rise with internal cell impedance-surge signals was observed within 600 h for cell composed of TPU–HNTs–LiTFSI–PE. The initial capacities of NCM|TPU–HNTs–LiTFSI–PE|Li and NCM|TPU–HNTs–LiFSI–PE|Li cells were 149 and 114 mAh g−1, with capacity retention rates of 83.52% and 89.99% after 300 cycles at 0.5 C, respectively. This study provides a valuable guideline for designing flexible SPCE, which shows great application prospect in the practice of ASSLB.

Low-cost, high-activity, non-precious metal electrocatalysts are needed to enhance the bifunctional oxygen activities of rechargeable Zn-Air batteries. In this study, a Fe-enriched FeNi3 inter-metallic nanoparticle/nitrogen-doped carbon (Fe-enriched-FeNi3/NC) electrocatalyst was designed and prepared using a facile method based on plasma engineering. The excess Fe-ions in the Fe-enriched FeNi3 nanoparticles led to a high degree of lattice distortion that produced abundant oxygen-active sites. The electrocatalyst exhibited excellent oxygen evolution reaction (OER) activity as well as favorable oxygen reduction reaction (ORR) activity in an alkaline electrolyte. In addition, the electrocatalyst revealed a lower potential difference (ΔE = 0.80 V vs. RHE) in a bifunctional oxygen reaction compared to that of the benchmark 20 wt% Pt/C + Ir/C (ΔE = 0.84 V vs. RHE), and most of the reported FeNi3 alloy-doped carbon catalysts. Based on DFT calculations, the lattice distortion in Fe-enriched-FeNi3/NC promoted a higher density of active electrons around the Fermi level. Owing to its great bifunctional oxygen activities, Fe-enriched FeNi3/NC was applied as an ORR/OER catalyst in the air cathode in a homemade zinc-air battery and exhibited an excellent discharge–charge voltage gap (0.89 V), peak power density (89 mW/cm2), and high specific capacity of 734 mAh/g at 20 mA/cm2, which outperformed the benchmark 20 wt% Pt/C + Ir/C electrocatalyst. In summary, this research provides a novel strategy to enhance the OER/ORR activities of transition metal-based alloys through lattice distortion defects. In addition, it provides a new pathway for achieving noble metal-free air cathode materials for the next generation Zn-air battery.

Designing a novel anode material with suitable elemental composition and bonding structure for improving the limited capacity and poor lithium-ion conductivity of lithium-ion batteries (LIBs) is still challenging. Here, guided by first-principles calculations, we report a higher crystal symmetric, cation-disordered zinc blende Zn0.5Ge0.5P anode material with high-capacity and high-rate capability owing to superior electron and lithium-ion transport compared to the parent allotrope chalcopyrite ZnGeP2. The Zn0.5Ge0.5P anode exhibits a large specific capacity of 1435 mA h g−1 with a high initial Coulombic efficiency of 92%. An amorphization–conversion–alloying reaction mechanism is proposed based on ex situ characterizations including X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. During lithiation, the material phase-changes through Li3P, LiZnGe, β-Li2ZnGe, and α-Li2ZnGe intermediates that provide suitable transport channels for fast diffusion of lithium ions. During delithiation, LiZn, Li15Ge4, and Li3P nanoparticles reassemble into Zn0.5Ge0.5P. A Zn0.5Ge0.5P–TiC–C composite with finer particle size and enhanced electronic conductivity exhibits an initial specific capacity of 1076 mA h g−1 and a capacity retention of 92.6% after 500 cycles.

Anatase TiO2 is considered as a promising anode material for sodium-ion batteries, but the inherent semiconductor properties and the sluggish Na+ diffusion kinetics limit its further development. To overcome these inherent drawbacks, heterojunction TiO2@TiOF2 constructed with two-dimensional nanosheets is prepared by the hydrothermal method. When heterojunction TiO2@TiOF2 is used as a sodium ion battery material, a stable cycling performance of up to 10 000 cycles can be achieved at a high current density of 5000 mA g−1, probably due to the heterojunction structure, the exposed (0 0 1) facet of TiO2 and the in situ formed NaF protective layer. Density functional theory (DFT) calculations further reveal that the heterostructure TiO2@TiOF2 nanosheets possess better electrical conductivity and lower formation energies of Na+ ions than those of the separated TiO2 and TiOF2. This work offers a new strategy to design novel heterojunction structures for the electrochemical sodium storage.

Mn-based layered oxides, as potential cathodes for potassium-ion batteries (PIBs), face major challenges such as consecutive phase transition, serious capacity loss, and sluggish K+ transport kinetics. Herein, Co–Mg co-substituted K0.45Co1/12Mg1/12Mn5/6O2 is designed as a promising cathode material for PIBs to conquer the above issues in this work. Co3+–Mg2+ ions occupying the Mn3+ sites are confirmed to effectively alleviate the Jahn–Teller distortion induced by Mn3+ ions. P3-K0.45Co1/12Mg1/12Mn5/6O2 exhibits highly reversible single-phase structural evolution during the K+ deintercalation/intercalation. In contrast, the pristine K0.45MnO2 electrode experiences incompletely reversible structural variation from a P′3 to P3 phase. The increase of structural stability in the Co–Mg co-substituted sample is the main reason leading to improved cycling stability. Moreover, K0.45Co1/12Mg1/12Mn5/6O2 delivers better rate capability resulting from faster K+ diffusion compared to K0.45MnO2. Therefore, Co–Mg co-substitution is an effective strategy to enhance the structural stability and electrochemical properties of Mn-based layered oxides in PIBs.

Transition metal oxides have high specific capacity as anode materials for lithium-ion battery. But aggregation of particles and volume expansion during lithiation/delithiation restrict their application. In this work, a three-dimensional hierarchical Ca3Co4O9 hollow fiber network assembled by nanosheets is prepared by a electrospinning combining with heat treatment method to overcome these issues and to boost its lithium storage performance. As-synthesized sample possesses excellent cyclic stability (578.6 mA h g−1 at 200 mA g−1 after 500 cycles) and rate performance (293.5 mA h g−1 at 5000 mA g−1), much better than those of commercial Co3O4. Furthermore, the fast kinetics of the three-dimensional Ca3Co4O9 hollow fiber network is also confirmed by the variable scan rates CV tests and the EIS measurements, which is dedicated to the specific hierarchical hollow fiber network structure that provides shorter ion transport distances and higher electrical conductivity. This work supplies a universal approach to improve the electrochemical performance of transition metal oxides for lithium ion batteries.

Zinc-air battery is one of the most promising next-generation energy conversion and storage systems. Green and low-cost catalysts with high oxygen reduction reaction (ORR) catalytic activity are desired to meet the requirements of Zinc-air batteries. Herein, poly-active centric Co3O4-CeO2/Co-N-C (ketjenblack carbon) catalysts were prepared by a facile method. The Co3O4 and CeO2 nanoparticles are uniformly anchored on the surface of Co and N doped carbon support. The half-wave potential of Co3O4-CeO2/Co-N-C in the rotating disk electrode testing is close to that of Pt/C. The Zn-air battery using Co3O4-CeO2/Co-N-C as the cathode catalyst can provide a high specific capacity of 728 mA h g−1 at 20 mA cm−2 and maintain a stable discharge voltage. The remarkable catalytic performance is mainly attributed to the synergistic effect among Co3O4, CeO2 and Co-N-C, the outstanding electrical conductivity and the large surface area. Benefitting from the high catalytic activity, environmental friendliness and the facile synthesis process, Co3O4-CeO2/Co-N-C catalyst lends itself well to a great prospect in the application of metal-air batteries.

Construction of three-dimensional (3D) composite lithium metal anodes (LMAs) based on Li melt-infusion into a 3D porous scaffold has been demonstrated to be effective for solving the issue of the considerable relative volume change of LMAs during Li plating/stripping. However, little attention has been paid to controllable regulation of the structure and interface of 3D composite LMAs. In this study, 3D composite LMAs, namely Li–AuLi3@CF electrodes, are firstly fabricated by infusion of molten Li into carbon fiber (CF) paper modified with nanoporous gold (NPG) which is converted to AuLi3 after infusion. We herein demonstrate a synergistic structure and interface engineering strategy realized by a simple and effective pre-stripping protocol to initially expose a portion of the 3D AuLi3@CF scaffold to create “PS-Li-AuLi3@CF” electrodes, which greatly boosted the electrochemical performance. Symmetrical Li|Li cells with PS-Li-AuLi3@CF electrodes show an overpotential of 111 ​mV after cycling at a current density of 0.5 ​mA ​cm−2 for 1800 ​h. Additionally, Li|LiFePO4 (LFP) and Li|sulfurized polyacrylonitrile (SPAN) full cells with PS-Li-AuLi3@CF electrodes exhibit a high capacity retention of 96.1% with a Coulombic efficiency (CE) of 99.2% after 1000 cycles at 5C, and a capacity retention of 70.6% with a CE of 99.8% after 1000 cycles at 2C, respectively. This work provides a simple and highly effective method for engineering the structure and interface of 3D composite LMAs to boost their electrochemical performance for high-energy-density rechargeable lithium metal batteries (LMBs).

Alloy anode with good reversibility of lithium plating/stripping and long cycling stability is considered as promising anode materials. Here, Cu–Sn alloy is used as the substrate for Li deposition to induce the most densely packed arrangement of Li atoms, thus presenting high lithiophilicity and improving Li plating behaviors. The LiFePO4-based full cell with the as-prepared dendrite-free Li metal anode retained at 85 mAh g−1 with a high coulombic efficiency of 99.5% after 300 cycles, presenting a capacity retention of 79.4%. This strategy provides a new perspective to structure dendrite-free Li anode for the next-generation high-energy density batteries.

As one of the most promising next-generation safe and green energy storage technologies, aqueous Zn-ion batteries have attracted considerable attention in recent years. However, their working mechanism is still controversial. Also, their performance needs to be further improved to meet the requirement of widespread applications. Herein, we developed a nanoflower-like MnO2/C composite with two-electron reaction pathway for use as a cathode material in aqueous Zn-ion batteries. Benefiting from the large specific surface area of the nanoflower-like structure, high conductivity of the carbon materials and the low crystallinity of birnessite-type MnO2, the Zn-ion battery using MnO2/C as the cathode material could carry out a deep and fast reaction via the Mn4+/Mn2+ two-electron pathway. At 300 mA g−1, the battery could retain a high specific capacity of 279.7 mA h g−1 after 300 cycles. The second electronic reaction process of Mn3+/Mn2+ could also work at a high current density. A high initial discharge capacity of more than 200 mA h g−1 was achieved at a high current density of 2000 mA g−1. A two-electron working mechanism of the layered-MnO2 cathode material is proposed. Due to the advantages of high capacity, high rate performance and good stability, the MnO2/C composite is a promising cathode material for aqueous Zn-ion batteries, which holds potential for applications in electric vehicles and grid energy storage.

Composite solid-state electrolytes (CSEs) that integrate the merits of different components are considered to be promising candidates for next-generation high-energy density lithium metal batteries. Herein, we have successfully designed a flexible CSE membrane consisting of the ceramic conducting Li1.3Al0.3Ti1.7(PO4)3 (LATP) filler, polyethylene oxide (PEO) matrix, and 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (BMP-TFSI) ionic liquid. In particular, the addition of ionic liquid (BMP-TFSI) can not only decrease the interface impedance between the polymer and LATP ceramic fillers and improve the ionic conductivity, but also prevent the adverse reaction between Ti4+ in LATP and Li metal and further enhance the interface stability. Benefitting from the synergistic effect of organic–inorganic hybrids, the obtained composite electrolyte membrane achieves an excellent ionic conductivity of 2.42 × 10−4 S cm−1 at 30 °C and a wide electrochemical stability window of 5 V (vs. Li+/Li). Moreover, the CSE membrane exhibits outstanding Li dendrite suppression capability, which is proved by galvanostatic Li plating/stripping tests for 1000 h. Assembled with this solid electrolyte membrane and a commercial LiFePO4 cathode, all-solid-state lithium metal batteries demonstrate superior rate capability and outstanding cycling stability at both 30 and 45 °C. These results demonstrate that such a flexible composite electrolyte is a promising alternative electrolyte for practical high-energy density all-solid-state batteries.

The construction of a lithiophilic phase on the surface of a current collector with a lithiophobic nature is an effective method to suppress Li dendrite growth by reducing the overpotential for Li nucleation and inducing the growth of homogeneous Li nuclei to obtain high-performance lithium metal anodes (LMAs). Nevertheless, the structural regulation of the lithiophilic phase and the underlying mechanism of lithiophilicity have been overlooked in previous studies. In this study, we designed a triporous, nanoporous AuLi3 (NPAuLi3) nanosheet-modified Ni foam (NF) (NPAuLi3@NF) composite current collector for use in LMAs. First principle calculations revealed that the lithiophilicity of the AuLi3 phase originates from the strong electronic interaction between the Au and Li atoms. The morphological characterization demonstrated that the as-designed NPAuLi3@NF current collector not only guided homogeneous Li nucleation and growth during the Li plating process, but also induced uniform Li removal during the Li stripping process, which effectively suppressed Li dendrite growth and formation of dead Li, leading to a boosted electrochemical performance in LMAs. The symmetric Li|Li cells with the NPAuLi3@NF-based LMAs could run stably for 1990 and 1420 h without cell failure at current densities of 1 and 2 mA cm−2 with a capacity of 2 mA h cm−2, respectively, and the Li@NPAuLi3@NF|LFP full cells showed an excellent capacity retention of 83.8% with a coulombic efficiency of 99.8% at 5C after 1000 cycles, and a good rate capability. This work provides insight into the design of the composition and structure of the lithiophilic phase on the surface of the current collector skeleton to obtain high-performance LMAs.

The short life span of lithium metal anodes (LMAs) due to dendrite growth and low coulombic efficiency (CE) has been regarded as the bottleneck in developing next-generation high-energy-density lithium metal based secondary batteries. Employing three-dimensional (3D) current collectors is one approach to reduce the effective current density and delay dendrite growth. Commercial Ni foam, in spite of its high electronic conductivity and 3D topology, has not been considered for this application due to its low specific surface area and lithiophobic nature. In this study, we develop a surface engineering strategy to uniformly coat lithiophilic AuLi3 particles on Ni foam skeletons through lithiation of electrodeposited gold nanoparticles. In comparison with the bare Ni foam, the AuLi3@Ni foam is more lithiophilic, significantly lowering the nucleation energy barrier and enhancing the uniformity for Li deposition. Such a structure results in effective suppression of Li dendrite growth in the void space of the foam. As a result, the AuLi3@Ni foam current collector based LMAs can run for 740 h without cell failure in a symmetric cell. Furthermore, the Li-AuLi3@Ni foam|LiFePO4 full cell shows an excellent capacity retention of 43.8% with a high CE of 99.2% at 1C for 500 cycles. This work further illustrates the critical importance of surface lithiophilicity in guiding lithium cycling and suggests engineering the skeleton surface of commercial metal foam current collectors is important to improve 3D structured LMAs.

Exploring highly active and stable bifunctional water-splitting electrocatalysts at ultra-high current densities is remarkably desirable. Herein, 3D nickel-iron phosphides nanosheets modified by MnO

The NiS2 nanosheet array on Ni foil (NiS2/NF) was prepared using an in situ growth strategy and sulfidation method and was used as the cathode of lithium sulfur battery. The unique nanostructure of the NiS2 nanosheet array can provide abundant active sites for the adsorption and chemical action of polysulfides. Compared with the sulfur powder coated pure NF (pure NF-S) for lithium sulfur battery, the sulfur powder coated NiS2/NF (NiS2/NF-S) electrode exhibits superior electrochemical performance. Specifically, the NiS2/NF-S delivered a high reversible capacity of 1007.5 mAh g−1 at a current density of 0.1 C (1 C= 1675 mA g−1) and kept 74.5% of the initial capacity at 1.0 C after 200 cycles, indicating the great promise of NiS2/NF-S as the cathode of lithium sulfur battery. In addition, the NiS2/NF-S electrode also showed satisfactory electrochemical performance when used as the cathode for sodium sulfur battery.