Ni‐rich layered LiNixCoyMn1−x−yO2 (LNCM) with Ni content over >90% is considered as a promising lithium ion battery (LIB) cathode, attributed by its low cost and high practical capacity. However, ...Ni‐rich LNCM inevitably suffers rapid capacity fading at a high state of charge due to the mechanochemical breakdown; in particular, the microcrack formation has been regarded as one of the main culprits for Ni‐rich layered cathode failure. To address these issues, Ni‐rich layered cathodes with a textured microstructure are developed by phosphorous and boron doping. Attributed by the textured morphology, both phosphorous‐ and boron‐doped cathodes suppress microcrack formation and show enhanced cycle stability compared to the undoped cathode. However, there exists a meaningful capacity retention difference between the doped cathodes. By adapting the various analysis techniques, it is shown that the boron‐doped Ni‐rich layered cathode displays better cycle stability not only by its ability to suppress microcracks during cycling but also by its primary particle morphology that is reluctant to oxygen evolution. The present work reveals that not only restraint of particle cracks but also suppression of oxygen release by developing the oxygen stable facets is important for further improvements in state‐of‐the‐art Li ion battery Ni‐rich layered cathode materials.
Herein, the effect of boron doping on oxygen stability in LiNi0.92Co0.04Mn0.04O2 (LNCM) lithium ion battery cathodes is systematically investigated using various measurements. The boron‐doped LNCM produces the textured microstructure with more oxygen stabilized facets, thus not only aiding in restraining the particle cracks but also effectively suppressing the oxygen evolution to improve the cycle stability.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Phosphorus‐rich 6‐MnP4 nanoparticles are synthesized via high energy mechanical milling (HEMM) and their electrochemical properties as an anode for lithium‐ion batteries (LIBs) and sodium‐ion ...batteries (SIBs) are investigated focusing on the electrochemical activity and reaction mechanism. The 6‐MnP4 nanoparticles with a triclinic structure (P‐1) are successfully synthesized by HEMM and they are composed of 5 to 20 nm‐sized crystallites. During the lithiation process, the MnP4 phase undertakes the sequential alloying (MnP4 + 7 Li+ + 7 e− → Li7MnP4) and conversion (Li7MnP4 + 5 Li+ + 5 e− → Mn0 + 4 Li3P) reactions. On the other hand, the MnP4 nanoparticles are directly converted to Mn0 and Na3P without the formation of an intermediate Na–Mn–P alloy phase during sodiation process. The MnP4 electrode shows high initial discharge and charge capacity (1876 and 1615 mAh g−1 for LIBs, and 1234 and 1028 mAh g−1 for SIBs) and high initial Coulombic efficiency (86% for LIBs and 83% for SIBs), indicating a promising candidate for high capacity anodes. In addition, the long‐term cyclability and high rate capability of MnP4 can be further improved through the formation of MnP4/graphene nanocomposites and vanadium substituted Mn0.75V0.25P4 solid solutions.
Phosphorus‐rich MnP4 nanoparticles are introduced as high capacity anodes for both lithium‐ion batteries (LIBs) and sodium‐ion batteries (SIBs). The MnP4 electrode shows a high electrochemical activity and a reversible capacity of 1615 and 1028 mAh g–1 respectively, with high initial coulombic efficiency of 86% and 83% for both LIBs and SIBs respectively, indicating a promising candidate for high capacity anodes.
Full text
Available for:
FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Tin phosphide (Sn4P3) has emerged as an anode for sodium ion batteries (SIBs) due to its high reversible capacity and low redox potential. Sn4P3 shows a synergistic Na-storage reaction to form ...Na15Sn4 and Na3P, but suffers from large volume expansion and Sn aggregation during the Na+ insertion–extraction resulting in poor cycle stability. Sn4P3 has also been considered a promising anode material for lithium ion batteries (LIBs), but very limited studies have been performed. Herein, core–shell Sn4P3–C (carbon) composite nanospheres are fabricated by carbonization/reduction and phosphorization of SnO2–GCP (glucose-derived, carbon-rich polysaccharide) nanospheres. The size of Sn4P3–C nanospheres is controlled to optimize their electrochemical performance as long-term stable anodes for SIBs and LIBs. Among them, the 140 nm-sized Sn4P3–C nanosphere electrode exhibits high reversible capacity, high rate capability, and ultra-long cycle stability as an anode for both SIBs and LIBs, delivering a high capacity of 420 mA h g−1 after 2000 cycles (SIBs) and 440 mA h g−1 after 500 cycles (LIBs) at a high current density of 2000 mA g−1. Hence, the Sn4P3–C nanospheres can be considered as a promising anode material for next generation SIBs and LIBs.
Highly porous carbon materials with a rationally designed pore structure can be utilized as reservoirs for metal or nonmetal components. The use of small‐sized metal or metal compound nanoparticles, ...completely encapsulated by carbon materials, has attracted significant attention as an effective approach to enhancing sodium ion storage properties. These materials have the ability to mitigate structural collapse caused by volume expansion during the charging process, enable short ion transport length, and prevent polysulfide elution. In this study, a concept of highly porous carbon‐coated carbon nanotube (CNT) porous microspheres, which serve as excellent reservoir materials is suggested and a porous microsphere is developed by encapsulating iron sulfide nanocrystals within the highly porous carbon‐coated CNTs using a sulfidation process. Furthermore, various sulfidation processes to determine the optimal method for achieving complete encapsulation are investigated by comparing the morphologies of diverse iron sulfide‐carbon composites. The fully encapsulated structure, combined with the porous carbon, provides ample space to accommodate the significant volume changes during cycling. As a result, the porous iron sulfide‐carbon‐CNT composite microspheres exhibited outstanding cycling stability (293 mA h g−1 over 600 cycles at 1 A g−1) and remarkable rate capability (100 mA h g−1 at 5 A g−1).
A concept of highly porous carbon‐coated carbon nanotube (CNT) porous microspheres, which serve as excellent reservoir materials is introduced for the first time. The highly porous nanostructured carbon with internal voids enables complete encapsulation of iron sulfide nanocrystals via optimal sulfidation method and the electrode showed excellent cycling stability for sodium‐ion batteries.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Despite being a leading candidate to meet stringent energy targets of Li-ion batteries, the lithium (Li) metal anode has yet to achieve Coulombic efficiency (CE) requirements for long cycle life ...(>99.9%). These limitations derive from the native solid electrolyte interphase (SEI) which, among multiple functions, stabilizes and protects deposited Li. The SEI also plays a critical role in regulating Li + exchange between the electrolyte and the electrode, but quantification of this effect has been non-straightforward, and a general relationship between Li + exchange and CE has not been clearly elucidated to date. Using electrochemical impedance spectroscopy and voltammetry, we report self-consistent Li + exchange values of native SEIs over a range of relevant electrolytes with CE spanning 78.0% to >99%. CE and its retention at high rates are found to be positively correlated with the rate of SEI Li + exchange. Additionally, SEI Li + exchange rates increased during cycling in high-CE electrolytes, in some cases by an order of magnitude to exceed 10 mA cm −2 , whereas for low-CE electrolytes they remained low (<1 mA cm −2 ), revealing a chemistry-dependent picture of SEI evolution with often-complex dynamics. The evolution in Li + exchange unique to high-CE electrolytes also provides insights into the role and effectiveness of the formation cycle on Cu current collectors upon the first plating step. Altogether, these findings indicate that Li + exchange governs several key processes related to Li deposition and cycling efficiency. Consequently, its quantification can help to guide future high-CE electrolyte design, particularly targeting high rates (>1 mA cm −2 ).
The realization of high performance Ni-rich layered cathodes remains a challenge because of the multiple degradation factors that concurrently operate during battery cycling. In particular, depletion ...of oxygen charge and consequent lattice-oxygen instability at deep charge state accelerate the subsequent chemomechanical degradation mechanisms. Among the proposed methodologies, doping has proven to be effective in enhancing the cathode cycle life by stabilizing the layered structure. Herein, we achieved the electrochemically stabilized Ni-rich LiNi
0.92
Co
0.04
Mn
0.04
O
2
through Zr doping, resulting in a 15% increase of the capacity retention after 100 cycles. In-depth investigations are conducted to unveil the effects of Zr doping on the layered cathode, and in particular, the critical role of Zr doping on the lattice oxygen stability is systematically studied. By combining state-of-the-art magnetometer characterization, X-ray analysis, and first-principles calculation, we reveal that Zr doping positively contributes the to lattice oxygen stability by alleviating the oxygen charge loss at deep charge, thereby improving the cathode electrochemical reversibility. Our findings provide an insight into the Zr doping mechanism and help to design Ni-rich layered oxides for future applications.
The suppression of oxygen oxidation is proposed as the critical origin of Zr doping on LiNi
0.92
Co
0.04
Mn
0.04
O
2
layered oxide LIB cathode material.
Silicon (Si) is considered to be one of the most promising anode candidates for next-generation lithium-ion batteries because of its high theoretical specific capacity and low discharge potential. ...However, its poor cyclability, caused by tremendous volume change during cycling, prevents commercial use of the Si anode. Herein, we demonstrate a high-performance Si anode produced via covalent bond formation between a commercially available Si nanopowder and a linear polymeric binder through an esterification reaction. For efficient ester bonding, polyacrylic acid, composed of −COOH groups, is selected as the binder, Si is treated with piranha solution to produce abundant −OH groups on its surface, and sodium hypophosphite is employed as a catalyst. The as-fabricated electrode exhibits excellent high rate capability and long cycle stability, delivering a high capacity of 1500 mA h g–1 after 500 cycles at a high current density of 1000 mA g–1 by effectively restraining the susceptible sliding of the binder, stabilizing the solid electrolyte interface layer, preventing the electrode delamination, and suppressing the Si aggregation. Furthermore, a full cell is fabricated with as-fabricated Si as an anode and commercially available LiNi0.6Mn0.2Co0.2O2 as a cathode, and its electrochemical properties are investigated for the possibility of practical use.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
V4P7 nanoparticles were synthesized via high-energy mechanical milling and their electrochemical properties as an anode for sodium-ion batteries were studied and compared with those of VO2(B)/Na and ...V4P7/Li cells, focusing on the electrochemical reaction mechanism and cycle performance. The V4P7 showed excellent cycling behavior even without any conductive material.
It has been widely suggested in literature that a lithium fluoride (LiF)-rich solid electrolyte interphase (SEI) affects Coulombic efficiency (CE) of the Li metal anode used with liquid electrolytes. ...Yet, the influence of LiF on Li metal deposition has been challenging to examine. Herein, we developed a method to synthesize LiF nanoscale particles with tunable sizes (30–300 nm) on Cu electrodes by electrochemical reduction of fluorinated gases under controlled discharge rates and capacities. The impact of LiF nanoparticles on overpotential and morphology of Li deposition was further studied in a conventional carbonate electrolyte. By cyclic voltammetry, Li plating overpotentials exhibit a clear correlation with the total surface area of LiF particles. Additionally, Li metal deposits (10
μ
Ah cm
−2
) nucleated under galvanostatic conditions (0.5 mA cm
−2
) on Cu/LiF showed increasing feature sizes with a lower average LiF particle size and higher coverage of LiF. However, no significant improvement in CE was observed for LiF-coated Cu. Our findings provide evidence that a particle-based mode of SEI fluorination can influence early-stage Li nucleation to a modest degree, and this effect is maximized when LiF is uniformly and densely distributed. However, sparser and larger LiF have vanishing or even detrimental effect on cycling performance.
Ni‐rich layered LiNi1−x−yCoxMnyO2 systems are the most promising cathode materials for high energy density Li‐ion batteries (LIBs). However, Ni‐rich cathode materials inevitably suffer from rapid ...capacity fading and poor rate capability owing to structural instability and unstable surface side reactions. Zr doping has proven to be an effective method to enhance the cycle and rate performances by stabilizing the structure and increasing the Li+ diffusion rate. Herein, effects of Zr‐doping on the structural stability and Li+ diffusion kinetics are thoroughly investigated in LiNi0.6Co0.2Mn0.2O2 (LNCM) cathode material using atomic‐resolution scanning transmission electron microscopy imaging, XRD Rietveld refinement, and density functional theory calculations. Zr doping mitigates the degree of cation mixing, decreases the structural transformation, and facilitates Li+ diffusion resulting in improved cyclic performance and rate capability. Based on the obtained results, an atomistic model is proposed to explain the effects of Zr doping on the structural stability and Li+ diffusion kinetics in LNCM cathode materials.
Vitamin Zr: The effect of Zr doping on the structural stability and Li+ diffusion kinetics in LiNi0.6Co0.2Mn0.2O2 cathode materials is investigated through atomistic characterization and density functional theory calculations. Zr doping mitigates the degree of cation mixing, decreases the structural transformation, and facilitates Li+ diffusion resulting in the improved cyclic performance and rate capability.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
