Xu Gao

Bio: Xu Gao is an academic researcher from Central South University. The author has contributed to research in topics: Cathode & Materials science. The author has an hindex of 12, co-authored 26 publications receiving 620 citations.

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

Abstract: 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 ZnMn2 O4 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.

Pseudo-Bonding and Electric-Field Harmony for Li-Rich Mn-Based Oxide Cathode

Abstract: The practical application of Li‐rich Mn‐based oxide cathode is predominately retarded by the capacity decline and voltage fading, associated with the structure distortion and anionic redox reactions. Here, a linkage‐functionalized modification approach to tackle these challenges via a synchronous lithium oxidation strategy is reported. The doping of Ce in the bulk phase activates the pseudo‐bonding effect, effectively stabilizing the lattice oxygen evolution and suppressing the structure distortion. Interestingly, it also induces the formation of spinel phase Li4Mn5O12 in the subsurface, which in turn constructs the phase boundaries, thereby arousing the interior self‐built‐in electric field to prevent the outward migration of bulk oxygen anions and boost the charge transfer. Moreover, the formed coating layer Li2CeO3 with oxygen vacancies accelerates Li+ diffusion and mitigates electrolyte cauterization. The corresponding cathode exhibits superior long‐cycle stability after 300 cycles with only a 0.013% capacity drop and 1.76 mV voltage decay per cycle. This work sheds new light on the development of Li‐rich Mn‐based oxide cathodes toward high energy density applications.

Nanoengineering of 2D MXene-Based Materials for Energy Storage Applications

Abstract: 2D MXene-based nanomaterials have attracted tremendous attention because of their unique physical/chemical properties and wide range of applications in energy storage, catalysis, electronics, optoelectronics, and photonics. However, MXenes and their derivatives have many inherent limitations in terms of energy storage applications. In order to further improve their performance for practical application, the nanoengineering of these 2D materials is extensively investigated. In this Review, the latest research and progress on 2D MXene-based nanostructures is introduced and discussed, focusing on their preparation methods, properties, and applications for energy storage such as lithium-ion batteries, sodium-ion batteries, lithium-sulfur batteries, and supercapacitors. Finally, the critical challenges and perspectives required to be addressed for the future development of these 2D MXene-based materials for energy storage applications are presented.

Potassium-ion batteries: outlook on present and future technologies

Abstract: The limited resources and uneven distribution of lithium stimulate strong motivation to develop new rechargeable batteries that use alternative charge carriers. Potassium-ion batteries (PIBs) are at the top of the list of alternatives because of the abundant raw materials and relatively high energy density, fast ion transport kinetics in the electrolyte, and low cost. However, several challenges still hinder the development of PIBs, such as low reversible capacity, poor rate performance, and inferior cycling stability. Research on the cathode is currently focused on developing materials with high energy density and cycling stability, mainly including layered transition metal oxides, polyanion compounds, organic compounds, etc. Anodes based on intercalation reactions, conversion reactions, and alloying with potassium are currently under development, and promising results have been published. This review comprehensively summarizes the research effort to date on the electrode material optimization (e.g., crystals, morphology, reaction mechanisms, and interface control), the synthesis methods, and the full cell fabrication for PIBs to enhance the electrochemical potassium storage and provide a platform for further development in this battery system.

Manganese and Vanadium Oxide Cathodes for Aqueous Rechargeable Zinc-ion Batteries: A Focused View on Performance, Mechanism and Developments

Abstract: The development of new battery technologies requires to be well established in the same era of lithium ion batteries (LIBs), a well commercialized technology, and the merits should surpass over oth...

Atomic Engineering Catalyzed MnO2 Electrolysis Kinetics for a Hybrid Aqueous Battery with High Power and Energy Density

Abstract: Research interest and achievements in zinc aqueous batteries, such as alkaline Zn//Mn, Zn//Ni/Co, Zn-air batteries, and near-neutral Zn-ion and hybrid ion batteries, have surged throughout the world due to their features of low-cost and high-safety. However, practical application of Zn-based secondary batteries is plagued by restrictive energy and power densities in which an inadequate output plateau voltage and sluggish kinetics are mutually accountable. Here, a novel paradigm high-rate and high-voltage Zn-Mn hybrid aqueous battery (HAB) is constructed with an expanded electrochemical stability window over 3.4 V that is affordable. As a proof of concept, catalyzed MnO2 /Mn2+ electrolysis kinetics is demonstrated in the HAB via facile introduction of Ni2+ into the electrolyte. Various techniques are employed, including in situ synchrotron X-ray powder diffraction, ex situ X-ray absorption fine structure, and electron energy loss spectroscopy, to reveal the reversible charge-storage mechanism and the origin of the boosted rate-capability. Density functional theory (DFT) calculations reveal enhanced active electron states and charge delocalization after introducing strongly electronegative Ni. Simulations of the reaction pathways confirm the enhanced catalyzed electrolysis kinetics by the facilitated charge transfer at the active O sites around Ni dopants. These findings significantly advance aqueous batteries a step closer toward practical low-cost application.

Molecular grafting towards high-fraction active nanodots implanted in N-doped carbon for sodium dual-ion batteries.

Abstract: Sodium-based dual-ion batteries (Na-DIBs) show a promising potential for large-scale energy storage applications due to the merits of environmental friendliness and low cost. However, Na-DIBs are generally subject to poor rate capability and cycling stability for the lack of suitable anodes to accommodate large Na+ ions. Herein, we propose a molecular grafting strategy to in situ synthesize tin pyrophosphate nanodots implanted in N-doped carbon matrix (SnP2O7@N-C), which exhibits a high fraction of active SnP2O7 up to 95.6 wt% and a low content of N-doped carbon (4.4 wt%) as the conductive framework. As a result, this anode delivers a high specific capacity ∼400 mAh g-1 at 0.1 A g-1, excellent rate capability up to 5.0 A g-1 and excellent cycling stability with a capacity retention of 92% after 1200 cycles under a current density of 1.5 A g-1. Further, pairing this anode with an environmentally friendly KS6 graphite cathode yields a SnP2O7@N-C||KS6 Na-DIB, exhibiting an excellent rate capability up to 30 C, good fast-charge/slow-discharge performance and long-term cycling life with a capacity retention of ∼96% after 1000 cycles at 20 C. This study provides a feasible strategy to develop high-performance anodes with high-fraction active materials for Na-based energy storage applications.