High-capacity Ni-rich layered oxides are promising cathode materials for secondary lithium-based battery systems. However, their structural instability detrimentally affects the battery performance ...during cell cycling. Here, we report an Al/Zr co-doped single-crystalline LiNi
Co
Mn
O
(SNCM) cathode material to circumvent the instability issue. We found that soluble Al ions are adequately incorporated in the SNCM lattice while the less soluble Zr ions are prone to aggregate in the outer SNCM surface layer. The synergistic effect of Al/Zr co-doping in SNCM lattice improve the Li-ion mobility, relief the internal strain, and suppress the Li/Ni cation mixing upon cycling at high cut-off voltage. These features improve the cathode rate capability and structural stabilization during prolonged cell cycling. In particular, the Zr-rich surface enables the formation of stable cathode-electrolyte interphase, which prevent SNCM from unwanted reactions with the non-aqueous fluorinated liquid electrolyte solution and avoid Ni dissolution. To prove the practical application of the Al/Zr co-doped SNCM, we assembled a 10.8 Ah pouch cell (using a 100 μm thick Li metal anode) capable of delivering initial specific energy of 504.5 Wh kg
at 0.1 C and 25 °C.
Mechanical integrity issues such as particle cracking are considered one of the leading causes of structural deterioration and limited long-term cycle stability for Ni-rich cathode materials of ...Li-ion batteries. Indeed, the detrimental effects generated from the crack formation are not yet entirely addressed. Here, applying physicochemical and electrochemical ex situ and in situ characterizations, the effect of Co and Mn on the mechanical properties of the Ni-rich material are thoroughly investigated. As a result, we successfully mitigate the particle cracking issue in Ni-rich cathodes via rational concentration gradient design without sacrificing the electrode capacity. Our result reveals that the Co-enriched surface design in Ni-rich particles benefits from its low stiffness, which can effectively suppress the formation of particle cracking. Meanwhile, the Mn-enriched core limits internal expansion and improve structural integrity. The concentration gradient design also promotes morphological stability and cycling performances in Li metal coin cell configuration.
Palladium is a promising material for electrochemical CO2 reduction to formate with high Faradaic efficiency near the equilibrium potential. It unfortunately suffers from problematic operation ...stability due to CO poisoning on surface. Here, it is demonstrated that alloying is an effective strategy to alleviate this problem. Mesoporous PdAg nanospheres with uniform size and composition are prepared from the co‐reduction of palladium and silver precursors in aqueous solution using dioctadecyldimethylammonium chloride as the structure‐directing agent. The best candidate can initiate CO2 reduction at zero overpotential and achieve high formate selectivity close to 100% and great stability even at <‐0.2 V versus reversible hydrogen electrode. The high selectivity and stability are believed to result from the electronic coupling between Pd and Ag, which lowers the d‐band center of Pd and thereby significantly enhances its CO tolerance, as evidenced by both electrochemical analysis and theoretical simulations.
Mesoporous PdAg nanospheres can enable electrochemical CO2 reduction to formate with high activity, selectivity, and, most remarkably, excellent stability superior to most previous reports. The great performance is believed to arise from the strong electronic coupling between Pd and Ag upon alloying, which effectively alleviates the CO poisoning on surface.
Defect engineering on electrode materials is considered an effective approach to improve the electrochemical performance of batteries since the presence of a variety of defects with different ...dimensions may promote ion diffusion and provide extra storage sites. However, manipulating defects and obtaining an in-depth understanding of their role in electrode materials remain challenging. Here, we deliberately introduce a considerable number of twin boundaries into spinel cathodes by adjusting the synthesis conditions. Through high-resolution scanning transmission electron microscopy and neutron diffraction, the detailed structures of the twin boundary defects are clarified, and the formation of twin boundary defects is attributed to agminated lithium atoms occupying the Mn sites around the twin boundary. In combination with electrochemical experiments and first-principles calculations, we demonstrate that the presence of twin boundaries in the spinel cathode enables fast lithium-ion diffusion, leading to excellent fast charging performance, namely, 75% and 58% capacity retention at 5 C and 10 C, respectively. These findings demonstrate a simple and effective approach for fabricating fast-charging cathodes through the use of defect engineering.
Abstract
High-energy density lithium-rich layered oxides are among the most promising candidates for next-generation energy storage. Unfortunately, these materials suffer from severe electrochemical ...degradation that includes capacity loss and voltage decay during long-term cycling. Present research efforts are primarily focused on understanding voltage decay phenomena while origins for capacity degradation have been largely ignored. Here, we thoroughly investigate causes for electrochemical performance decline with an emphasis on capacity loss in the lithium-rich layered oxides, as well as reaction pathways and kinetics. Advanced synchrotron-based X-ray two-dimensional and three-dimensional imaging techniques are combined with spectroscopic and scattering techniques to spatially visualize the reactivity at multiple length-scales on lithium- and manganese-rich layered oxides. These methods provide direct evidence for inhomogeneous manganese reactivity and ionic nickel rearrangement. Coupling deactivated manganese with nickel migration provides sluggish reaction kinetics and induces serious structural instability in the material. Our findings provide new insights and further understanding of electrochemical degradation, which serve to facilitate cathode material design improvements.
Modern sustainability challenges in recent years have warranted the development of new energy storage technologies. Practical realization of the lithium–O2 battery holds great promise for ...revolutionizing energy storage as it holds the highest theoretical specific energy of any rechargeable battery yet discovered. However, the complete realization of Li–O2 batteries necessitates ambient air operations, which presents quite a few challenges, as carbon dioxide (CO2) and water (H2O) contaminants introduce unwanted byproducts from side reactions that greatly affect battery performance. Although current research has thoroughly explored the beneficial incorporation of CO2, much mystery remains over the inconsistent effects of H2O. The presence of water in both the cathode and electrolyte has been observed to alter reaction mechanisms differently, resulting in a diverse range of effects on voltage, capacity, and cyclability. Moreover, recent preliminary research with catalysts and redox mediators has attempted to utilize the presence of water to the battery's benefit. Here, the key mechanism discrepancies of water‐afflicted Li–O2 batteries are presented, concluding with a perspective on future research directions for nonaqueous Li–O2 batteries.
Water impurities can significantly affect Li–O2 electrochemistry. An overview of recent developments of Li–O2/H2O batteries is presented, aiming at gaining a better understanding of Li–O2/H2O batteries to facilitate future research progress in this emerging field.
Historically long accepted to be the singular root cause of capacity fading, transition metal dissolution has been reported to severely degrade the anode. However, its impact on the cathode behavior ...remains poorly understood. Here we show the correlation between capacity fading and phase/surface stability of an LiMn
O
cathode. It is revealed that a combination of structural transformation and transition metal dissolution dominates the cathode capacity fading. LiMn
O
exhibits irreversible phase transitions driven by manganese(III) disproportionation and Jahn-Teller distortion, which in conjunction with particle cracks results in serious manganese dissolution. Meanwhile, fast manganese dissolution in turn triggers irreversible structural evolution, and as such, forms a detrimental cycle constantly consuming active cathode components. Furthermore, lithium-rich LiMn
O
with lithium/manganese disorder and surface reconstruction could effectively suppress the irreversible phase transition and manganese dissolution. These findings close the loop of understanding capacity fading mechanisms and allow for development of longer life batteries.
The Li–CO2 battery is a promising energy storage device for wearable electronics due to its long discharge plateau, high energy density, and environmental friendliness. However, its utilization is ...largely hindered by poor cyclability and mechanical rigidity due to the lack of a flexible and durable catalyst electrode. Herein, flexible fiber‐shaped Li–CO2 batteries with ultralong cycle‐life, high rate capability, and large specific capacity are fabricated, employing bamboo‐like N‐doped carbon nanotube fiber (B‐NCNT) as flexible, durable metal‐free catalysts for both CO2 reduction and evolution reactions. Benefiting from high N‐doping with abundant pyridinic groups, rich defects, and active sites of the periodic bamboo‐like nodes, the fabricated Li–CO2 battery shows outstanding electrochemical performance with high full‐discharge capacity of 23 328 mAh g−1, high rate capability with a low potential gap up to 1.96 V at a current density of 1000 mA g−1, stability over 360 cycles, and good flexibility. Meanwhile, the bifunctional B‐NCNT is used as the counter electrode for a fiber‐shaped dye‐sensitized solar cell to fabricate a self‐powered fiber‐shaped Li–CO2 battery with overall photochemical–electric energy conversion efficiency of up to 4.6%. Along with a stable voltage output, this design demonstrates great adaptability and application potentiality in wearable electronics with a breath monitor as an example.
A self‐powered fiber‐shaped Li–CO2 battery with overall photochemical–electric energy conversion efficiency of up to 4.6% is fabricated using bifunctional bamboo‐like N‐doped carbon nanotube fiber as the cathode for the Li–CO2 battery and as the counter electrode for the dye‐sensitized solar cells simultaneously. The fiber‐shaped Li–CO2 batteries show high specific capacity, long cycle life, and high flexibility.
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