H+‐Insertion Boosted α‐MnO2 for an Aqueous Zn‐Ion Battery

Rechargeable Zn/MnO₂ batteries using mild aqueous electrolytes are attracting extensive attention due to their low cost, high safety, and environmental friendliness. However, the charge‐storage mechanism involved remains a topic of controversy so far. Also, the practical energy density and cycling stability are still major issues for their applications. Herein, a free‐standing α‐MnO₂ cathode for aqueous zinc‐ion batteries (ZIBs) is directly constructed with ultralong nanowires, leading to a rather high energy density of 384 mWh g^?1 for the entire electrode. Greatly, the H⁺/Zn²⁺ coinsertion mechanism of α‐MnO₂ cathode for aqueous ZIBs is confirmed by a combined analysis of in situ X‐ray diffractometry, ex situ transmission electron microscopy, and electrochemical methods. More interestingly, the Zn²⁺‐insertion is found to be less reversible than H⁺‐insertion in view of the dramatic capacity fading occurring in the Zn²⁺‐insertion step, which is further evidenced by the discovery of an irreversible ZnMn₂O₄ layer at the surface of α‐MnO₂. Hence, the H⁺‐insertion process actually plays a crucial role in maintaining the cycling performance of the aqueous Zn/α‐MnO₂ battery. This work is believed to provide an insight into the charge‐storage mechanism of α‐MnO₂ in aqueous systems and paves the way for designing aqueous ZIBs with high energy density and long‐term cycling ability.     

Enhanced zinc storage performance of mixed valent manganese oxide for flexible coaxial fiber zinc-ion battery by limited reduction control

While manganese-based cathodes have been intensively studied for zinc-ion batteries (ZIBs),the limited rate capability and cycle life have always been a difficult problem to be solved.Here,we report a mixed valent manganese oxide (MnOx) cathode with superior electrochemical performance,which exhibits a high specific capacity of 450 mA h/g at 0.2 C and a satisfactory specific capacity of 158.3 mA h/g at a high rate of 5 C.The mixed cathode system reduces the charge transfer resistance,and show good surface stability and adsorption properties,so it is beneficial for the storage of Zn2+.Meanwhile,coaxial fiber ZIBs (CFZIBs) with splendid flexibility are assembled utilizing the elaborately prepared cathode material.The CFZIBs achieve a reversible capacity of 255.8 mA h/g and the capacity retention rate is as high as 80 ％ after 1000 bending deformations.This study provides new opportunities for designing ZIBs with high performance and high flexibility.     

Layered Ca0.28MnO2·0.5H2O as a High Performance Cathode for Aqueous Zinc‐Ion Battery

Aqueous zinc‐ion batteries are promising candidates for grid‐scale energy storage because of their intrinsic safety, low cost, and high energy intensity. However, lack of suitable cathode materials with both excellent rate performance and cycling stability hinders further practical application of aqueous zinc‐ion batteries. Here, a nanoflake‐self‐assembled nanorod structure of Ca_0.28MnO₂·0.5H₂O as Zn‐insertion cathode material is designed. The Ca_0.28MnO₂·0.5H₂O exhibits a reversible capacity of 298 mAh g^?1 at 175 mA g^?1 and long‐term cycling stability over 5000 cycles with no obvious capacity fading, which indicates that the per‐insertion of Ca ions and water can significantly improve reversible insertion/extraction stability of Zn²⁺ in Mn‐based layered type material. Further, its charge storage mechanism, especially hydrogen ions, is elucidated. A comprehensive study suggests that the intercalation of hydrogen ions in the first discharge plat is controled by both pH value and type of anion of electrolyte. Further, it can stabilize the Ca_0.28MnO₂·0.5H₂O cathode and facilitate the following insertion of Zn²⁺ in 1 m ZnSO₄/0.1 m MnSO₄ electrolyte. This work can enlighten and promote the development of high‐performance rechargeable aqueous zinc‐ion batteries.     

Triggering High Capacity and Superior Reversibility of Manganese Oxides Cathode via Magnesium Modulation for Zn//MnO2 Batteries

Aqueous zinc-ion batteries (ZIBs) have attracted extensive attention in recent years because of its high volumetric energy density, the abundance of zinc resources, and safety. However, ZIBs still suffer from poor reversibility and sluggish kinetics derived from the unstable cathodic structure and the strong electrostatic interactions between bivalent Zn²⁺ and cathodes. Herein, magnesium doping into layered manganese dioxide (Mg–MnO₂) via a simple hydrothermal method as cathode materials for ZIBs is proposed. The interconnected nanoflakes of Mg–MnO₂ possess a larger specific surface area compared to pristine δ-MnO₂, providing more electroactive sites and boosting the capacity of batteries. The ion diffusion coefficients of Mg–MnO₂ can be enhanced due to the improved electrical conductivity by doped cations and oxygen vacancies in MnO₂ lattices. The assembled Zn//Mg–MnO₂ battery delivers a high specific capacity of 370 mAh g⁻¹ at a current density of 0.6 A g⁻¹. Furthermore, the reaction mechanism confirms that Zn²⁺ insertion occurred after a few cycles of activation reactions. Most important, the reversible redox reaction between Zn²⁺ and MnOOH is found after several charge–discharge processes, promoting capacity and stability. It believes that this systematic research enlightens the design of high-performance of ZIBs and facilitates the practical application of Zn//MnO₂ batteries.     

Structure-Controlled Carbon Hosts for Dendrite-Free Aqueous Zinc Batteries

The surging demand for environmental-friendly and safe electrochemical energy storage systems has driven the development of aqueous zinc (Zn)-ion batteries (ZIBs). However, metallic Zn anodes suffer from severe dendrite growth and large volume change, resulting in a limited lifetime for aqueous ZIB applications. Here, it is shown that 3D mesoporous carbon (MC) with controlled carbon and defect configurations can function as a highly reversible and dendrite-free Zn host, enabling the stable operation of aqueous ZIBs. The MC host has a structure-controlled architecture that contains optimal sp²-carbon and defect sites, which results in an improved initial nucleation energy barrier and promotes uniform Zn deposition. As a consequence, the MC host shows outstanding Zn plating/stripping performance over 1000 cycles at 2 mA cm⁻² and over 250 cycles at 6 mA cm⁻² in asymmetric cells. Density functional theory calculations further reveal the role of the defective sp²-carbon surface in Zn adsorption energy. Moreover, a full cell based on Zn@MC900 anode and V₂O₅ cathode exhibits remarkable rate performance and cycling stability over 3500 cycles. These results establish a structure-mechanism-performance relationship of the carbon host as a highly reversible Zn anode for the reliable operation of ZIBs.     

Elucidating the Reaction Mechanism of Mn2+ Electrolyte Additives in Aqueous Zinc Batteries

Aqueous zinc batteries (ZIBs) have attracted considerable attention in recent years because of their high safety and eco-friendly features. Numerous studies have shown that adding Mn²⁺ salts to ZnSO₄ electrolytes enhanced overall energy densities and extended the cycling life of Zn/MnO₂ batteries. It is commonly believed that Mn²⁺ additives in the electrolyte inhibit the dissolution of MnO₂ cathode. To better understand the role of Mn²⁺ electrolyte additives, the ZIB using a Co₃O₄ cathode instead of MnO₂ in 0.3 m MnSO₄ + 3 m ZnSO₄ electrolyte is built to avoid interference from MnO₂ cathode. As expected, the Zn/Co₃O₄ battery exhibits electrochemical characteristics nearly identical to those of Zn/MnO₂ batteries. Operando synchrotron X-ray diffraction (XRD), ex situ X-ray absorption spectroscopy (XAS), and electrochemical analyses are carried out to determine the reaction mechanism and pathway. This work demonstrates that the electrochemical reaction occurring at cathode involves a reversible Mn²⁺/MnO₂ deposition/dissolution process, while a chemical reaction of Zn²⁺/Zn₄SO₄(OH)₆∙5H₂O deposition/dissolution is involved during part of the charge/discharge cycle due to the change in the electrolyte environment. The reversible Zn²⁺/Zn₄SO₄(OH)₆∙5H₂O reaction contributes no capacity and lowers the diffusion kinetics of the Mn²⁺/MnO₂ reaction, which prevents the operation of ZIBs at high current densities.     

Rechargeable Aqueous Zinc‐Ion Battery Based on Porous Framework Zinc Pyrovanadate Intercalation Cathode

In this work, a microwave approach is developed to rapidly synthesize ultralong zinc pyrovanadate (Zn₃V₂O₇(OH)₂·2H₂O, ZVO) nanowires with a porous crystal framework. It is shown that our synthesis strategy can easily be extended to fabricate other metal pyrovanadate compounds. The zinc pyrovanadate nanowires show significantly improved electrochemical performance when used as intercalation cathode for aqueous zinc–ion battery. Specifically, the ZVO cathode delivers high capacities of 213 and 76 mA h g^?1 at current densities of 50 and 3000 mA g^?1, respectively. Furthermore, the Zn//ZVO cells show good cycling stability up to 300 cycles. The estimated energy density of this Zn cell is ≈214Wh kg^?1, which is much higher than commercial lead–acid batteries. Significant insight into the Zn‐storage mechanism in the pyrovanadate cathodes is presented using multiple analytical methods. In addition, it is shown that our prototype device can power a 1.5 V temperature sensor for at least 24 h.     

VO2·0.2H2O nanocuboids anchored onto graphene sheets as the cathode material for ultrahigh capacity aqueous zinc ion batteries

Aqueous Zinc-ion batteries (ZIBs), using zinc negative electrode and aqueous electrolyte, have attracted great attention in energy storage field due to the reliable safety and low-cost. A composite material comprised of VO₂·0.2H₂O nanocuboids anchored on graphene sheets (VOG) is synthesized through a facile and efficient microwave-assisted solvothermal strategy and is used as aqueous ZIBs cathode material. Owing to the synergistic effects between the high conductivity of graphene sheets and the desirable structural features of VO₂·0.2H₂O nanocuboids, the VOG electrode has excellent electronic and ionic transport ability, resulting in superior Zn ions storage performance. The Zn/VOG system delivers ultrahigh specific capacity of 423 mAh·g⁻¹ at 0.25 A·g⁻¹ and exhibits good cycling stability of up to 1,000 cycles at 8 A·g⁻¹ with 87% capacity retention. Systematical structural and elemental characterizations confirm that the interlayer space of VO₂·0.2H₂O nanocuboids can adapt to the reversible Zn ions insertion/extraction. The as-prepared VOG composite is a promising cathode material with remarkable electrochemical performance for low-cost and safe aqueous rechargeable ZIBs.

     

Bi-MOF Modulating MnO2 Deposition Enables Ultra-Stable Cathode-Free Aqueous Zinc-Ion Batteries

The Mn-based materials are considered as the most promising cathodes for zinc-ion batteries (ZIBs) due to their inherent advantages of safety, sustainability and high energy density, however suffer from poor cyclability caused by gradual Mn²⁺ dissolution and irreversible structural transformation. The mainstream solution is pre-adding Mn²⁺ into the electrolyte, nevertheless faces the challenge of irreversible Mn²⁺ consumption results from the MnO₂ electrodeposition reaction (Mn²⁺ → MnO₂). This work proposes a “MOFs as the electrodeposition surface” strategy, rather than blocking it. The bismuth (III) pyridine-3,5-dicarboxylate (Bi-PYDC) is selected as the typical electrodeposition surface to regulate the deposition reaction from Mn²⁺ to MnO₂. Because of the unique less hydrophilic and manganophilic nature of Bi-PYDC for Mn²⁺, a moderate MnO₂ deposition rate is achieved, preventing the electrolyte from rapidly exhausting Mn²⁺. Simultaneously, the intrinsic stability of deposited R-MnO₂ is enhanced by the slowly released Bi³⁺ from Bi-PYDC reservoir. Furthermore, Bi-PYDC shows the ability to accommodate H⁺ insertion/extraction. Benefiting from these merits, the cathode-free ZIB using Bi-PYDC as the electrodeposition surface for MnO₂ shows an outstanding cycle lifespan of more than 10 000 cycles at 1 mA cm^-2. This electrode design may stimulate a new pathway for developing cathode free long-life rechargeable ZIBs.     

Interfacial Engineering Coupled Valence Tuning of MoO3 Cathode for High‐Capacity and High‐Rate Fiber‐Shaped Zinc‐Ion Batteries

Aqueous Zn‐ion batteries (ZIBs) have garnered the researchers' spotlight owing to its high safety, cost effectiveness, and high theoretical capacity of Zn anode. However, the availability of cathode materials for Zn ions storage is limited. With unique layered structure along the [010] direction, α‐MoO₃ holds great promise as a cathode material for ZIBs, but its intrinsically poor conductivity severely restricts the capacity and rate capability. To circumvent this issue, an efficient surface engineering strategy is proposed to significantly improve the electric conductivity, Zn ion diffusion rate, and cycling stability of the MoO₃ cathode for ZIBs, thus drastically promoting its electrochemical properties. With the synergetic effect of Al₂O₃ coating and phosphating process, the constructed Zn//P‐MoO_3?x@Al₂O₃ battery delivers impressive capacity of 257.7 mAh g^?1 at 1 A g^?1 and superior rate capability (57% capacity retention at 20 A g^?1), dramatically surpassing the pristine Zn//MoO₃ battery (115.8 mAh g^?1; 19.7%). More importantly, capitalized on polyvinyl alcohol gel electrolyte, an admirable capacity (19.2 mAh cm^?3) as well as favorable energy density (14.4 mWh cm^?3; 240 Wh kg^?1) are both achieved by the fiber‐shaped quasi‐solid‐state ZIB. This work may be a great motivation for further research on molybdenum or other layered structure materials for high‐performance ZIBs.     

一种具有高能量密度、长循环寿命的水基可充电锰酸锂/锌实用电池

本文报道了一种达到实际使用规格的水基可充电锌离子大电池,该电池以锰酸锂为正极材料、锌粉为负极材料,电流10 A时其能量密度可达80 W h kg^-1,成本低于0.4 RMB kg^-1.该电池体系使用一种专门开发的石墨-尼龙复合集流体作为正极集流体,该复合集流体具有耐腐蚀性强、重量轻、价格便宜的特点.通过向电解液中添...     

Promoting the Na+-storage of NiCo2S4 hollow nanospheres by surfacing Ni-B nanoflakes

Sodium ion battery(SIB)is considered as the potential alternative for next generation energy system to succeed the lithium ion battery(LIB)due to the low price and vast abundance of Na resource.Ternary metal sulfide is identified as an important redox conversion type of negative electrode for SIB.In this study,amorphous nickel boride(Ni-B)nanoflakes are introduced into the hollow Ni-Co sulfide nanospheres by a facile in situ solution growth route to promote the electrochemical performance of Na+-storage.Elec-trochemical measurements demonstrate that the Ni-B component could effectively improve the redox kinetics of the conversion reaction and structural stability during long-term Na+insertion/extraction.For example,the NiCo2S4@Ni-B composites display a high reversible capacity of 251.9 mA h g-1 at the current density of 1.0 A g-1 after 200 cycles,much higher than that of bare NiCo2S4(37.4 mA h g-1 at 1.0 A g-1 after 200 cycles).As a consequence,these results demonstrate a new sight to explore heterostructures of mixed metal-sulfides electrode materials with superior Na+-storage performances.     

Insights into the Ti4+ doping in P2-type Na0.67Ni0.33Mn0.52Ti0.15O2 for enhanced performance of sodium-ion batteries

Due to the sodium abundance and availability,sodium-ion batteries (SIBs) have the potential to meet the worldwide growing demand of electrical energy storage.P2-type sodium transition-metal layer oxides with a high energy density are considered as the most promising cathode materials for SIBs.We present here a detailed study of the enhanced rate capability and cyclic stability of the Ti-doped Na0.67Ni0.33Mn0.67O2 cathode material.The combined analysis of ex-situ X-ray absorption fine structure (XAFS) spectroscopy,aberration-corrected high resolution transmission electron microscopy (AB-HRTEM) and X-ray diffraction (XRD) show that the strong Ti-O bond in the transition metal layers stabilizes the local structure,destroy the Na+-vacancy ordering and arrest the irreversible multiphase transformation that occurs during the intercalation/deintercalation process.Actually,Na0.67Ni0.33Mn0.52Ti0.15O2 exhibits a reversible capacity of 89.6 mA h g-1 even at 5 C,an excellent cyclability with 88.78 ％ capacity retention after 200 cycles at 0.5 C.This study provides a better understanding in optimization of the design of high-energy cathode materials based on titanium doped layered oxides for SIBs.     

富锂锰基正极材料Li1.2Ni0.13Co0.13Mn0.54O2的Zn2+掺杂改性

采用高温固相合成法制备富锂锰基正极材料Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54-x)Zn_xO_2(x=0,0.03,0.06,0.10),Zn~(2+)掺杂对Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.54)O_2的表面特性和电化学性能都有影响。通过X射线衍射(XRD)、扫描电子显微镜(SEM)、拉曼光谱分析、充放电测试、倍率特性测试、循环性能测试,分析了该合成材料的晶体结构、形貌特征、微观结构和电化学性能。富锂锰基正极材料为a-NaFeO_2层状结构,R-3m空间群,结晶度高,结构稳定性好,其中Li_(1.2)Ni_(0.13)Co_(0.13)Mn_(0.48)Zn_(0.06)O_2的电化学性能较好。掺杂Zn~(2+)可以提高富锂锰基正极材料的充放电比容量、倍率性能、循环性能等电化学性能。     

Crystalline and amorphous MnO2 cathodes with open framework enable high-performance aqueous zinc-ion batteries

Currently, δ-MnO₂ is one of the popularly studied cathode materials for aqueous zinc-ion batteries (ZIBs) but impeded by the sluggish kinetics of Zn²⁺ and the Mn cathode dissolution. Here, we report our discovery in the study of crystalline/amorphous MnO₂ (disordered MnO₂), prepared by a simple redox reaction in the order/disorder engineering. This disordered MnO₂ cathode material, having open framework with more active sites and more stable structure, shows improved electrochemical performance in 2 mol·L⁻¹ ZnSO₄/0.1 mol·L⁻¹ MnSO₄ aqueous electrolyte. It delivers an ultrahigh discharge specific capacity of 636 mA·h·g⁻¹ at 0.1 A·g⁻¹ and remains a large discharge capacity of 216 mA·h·g⁻¹ even at a high current density of 1 A·g⁻¹ after 400 cycles. Hence disordered MnO₂ could be a promising cathode material for aqueous ZIBs. The storage mechanism of the disordered MnO₂ electrode is also systematically investigated by structural and morphological examinations of ex situ, ultimately proving that the mechanism is the same as that of the δ-MnO₂ electrode. This work may pave the way for the possibility of using the order/disorder engineering to introduce novel properties in electrode materials for high-performance aqueous ZIBs.     

富锂正极材料Li1+x[Ni0.36Mn0.64]1-xO2的制备及电化学性能研究

采用氢氧化物共沉淀-高温固相焙烧法合成了富锂正极材料Li1+x[Ni0.36Mn0.64]1-xO2(x=0.12,0.15,0.18,0.2)。采用XRD表征其结构,SEM表征其形貌,恒电流充放电和循环伏安测试其电化学性能。其中,XRD结果表明各样品都具有α-NaFeO2型层状结构。结果表明:室温下以30mA/g的电流密度,在4.6~2.75V的电压范围内充放电,x=0.15的首次放电比容量为237.9mAh/g,经50次循环后容量保持率为98%。研究发现,层状富锂镍锰正极材料中的Li2MnO3组分在充放电过程中会逐渐向尖晶石相转变,这是容量衰减的主要原因。     

LiNi0.5Co0.2Mn0.3O2@WO3复合正极材料的制备与性能

为改善LiNi_0.5Co_0.2Mn_0.3O₂（NCM）锂离子电池三元正极材料的电化学性能,采用液相蒸发法将WO₃包覆于NCM表面,得到NCM@WO₃复合正极材料。通过XRD、SEM和TEM对NCM@WO₃复合材料的结构和形貌进行表征,利用充放电测试、循环伏安及交流阻抗测试对其电化学性能进行表征。结果表明,当WO₃包覆量为3wt%时,NCM@WO₃复合材料性能最佳,在0.5 C下的首次放电比容量为179.9 mA·hg-1,不可逆容量损失降低至42.4 mA·hg-1,循环50圈后容量保持率为98.3%。WO₃的包覆提高了锂离子扩散速率,减少了电极材料与电解液的副反应,NCM@WO₃复合材料的电化学性能得到提升。      

Ultrathin VSe2 Nanosheets with Fast Ion Diffusion and Robust Structural Stability for Rechargeable Zinc‐Ion Battery Cathode

The realizing of high‐performance rechargeable aqueous zinc‐ion batteries (ZIBs) with high energy density and long cycling life is promising but still challenging due to the lack of suitable layered cathode materials. The work reports the excellent zinc‐ion storage performance as‐observed in few‐layered ultrathin VSe₂ nanosheets with a two‐step Zn²⁺ intercalation/de‐intercalation mechanism verified by ex situ X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) characterizations. The VSe₂ nanosheets exhibit a discharge plateau at 1.0–0.7 V, a specific capacity of 131.8 mAh g^?1 (at 0.1 A g^?1), and a high energy density of 107.3 Wh kg^?1 (at a power density of 81.2 W kg^?1). More importantly, outstanding cycle stability (capacity retention of 80.8% after 500 cycles) without any activation process is achieved. Such a prominent cyclic stability should be attributed to its fast Zn²⁺ diffusion kinetics (D_Zn²⁺ ≈ 10^?8 cm^?2 s^?1) and robust structural/crystalline stability. Density functional theory (DFT) calculation further reveals a strong metallic characteristic and optimal zinc‐ion diffusion pathway with a hopping energy barrier of 0.91 eV. The present finding implies that 2D ultrathin VSe₂ is a very promising cathode material in ZIBs with remarkable battery performance superior to other layered transitional metal dichalcogenides.     

Low-temperature strategy to synthesize single-crystal LiNi0.8Co0.1Mn0.1O2 with enhanced cycling performances as cathode material for lithium-ion batteries

With high reversible capacities of more than 200 mAh/g,Ni-rich layered oxides Li[NixCoyMn1-x-y]O2(x≥0.6)serve as the most promising cathode materials for lithiu...     

Boosting High-Rate Zinc-Storage Performance by the Rational Design of Mn2O3 Nanoporous Architecture Cathode

Manganese oxides are regarded as one of the most promising cathode materials in rechargeable aqueous Zn-ion batteries(ZIBs)because of the low price and high security.However,the practical application of Mn2O3 in ZIBs is still plagued by the low specific capacity and poor rate capability.Herein,highly crystalline Mn2O3 materials with interconnected mesostructures and controllable pore sizes are obtained via a ligand-assisted self-assembly process and used as high-performance electrode materials for reversible aqueous ZIBs.The coordination degree between Mn2+and citric acid ligand plays a crucial role in the formation of the mesostructure,and the pore sizes can be easily tuned from 3.2 to 7.3 nm.Ascribed to the unique feature of nanoporous architectures,excellent zinc-storage performance can be achieved in ZIBs during charge/discharge processes.The Mn2O3 electrode exhibits high reversible capacity(233 mAh g−1 at 0.3 A g−1),superior rate capability(162 mAh g−1 retains at 3.08 A g−1)and remarkable cycling durability over 3000 cycles at a high current rate of 3.08 A g−1.Moreover,the corresponding electrode reaction mechanism is studied in depth according to a series of analytical methods.These results suggest that rational design of the nanoporous architecture for electrode materials can effectively improve the battery performance.