Tuning the Nanoarea Interfacial Properties for the Improved Performance of Li-Rich Polycrystalline Li-Mn‑O Spinel

The nontoxicity and low cost make LiMn2O4 a competitive cathode material for lithium-ion batteries. LiMn2O4 has a high theoretical capacity (296 mAh g–1) when cycled in the 3 and 4 V regions. However, it displays a low practical capacity (∼120 mAh g–1) because of the unavailability of the 3 V region caused by severe Jahn–Teller distortion. The present work investigated the full utilization of LiMn2O4 in both 3 and 4 V by tuning the nanoscale interfacial properties. Li-rich structures at the surface and interface of the spinel material and nanograin strain were introduced to improve the performances and were achieved by grinding LiMn2O4 and Li2O at 700 rpm for 10 h under an argon atmosphere. The product shows a high initial discharge capacity of 287.9 mAh g–1 at 0.05 C between 1.2 and 4.6 V and retains 83.2% of the capacity after 50 cycles. The nanoscale interfacial structure was clarified by spherical aberration-corrected microscopy and XRD refinement, and complex occupancies of Li and Mn were found at the interface. A correlation between the interfacial properties and electrochemical performance was established, and the improved performance could be attributed to the polycrystalline nature of the material, the unique Li-rich interfacial structure, and the slightly elevated valence state of Mn. The present results may provide insight for further evaluating the complex mechanism of controlling the electrochemical performance of LiMn2O4

Tuning the Nanoarea Interfacial Properties for the Improved Performance of Li-Rich Polycrystalline Li-Mn‑O Spinel

The nontoxicity and low cost make LiMn2O4 a competitive cathode material for lithium-ion batteries. LiMn2O4 has a high theoretical capacity (296 mAh g–1) when cycled in the 3 and 4 V regions. However, it displays a low practical capacity (∼120 mAh g–1) because of the unavailability of the 3 V region caused by severe Jahn–Teller distortion. The present work investigated the full utilization of LiMn2O4 in both 3 and 4 V by tuning the nanoscale interfacial properties. Li-rich structures at the surface and interface of the spinel material and nanograin strain were introduced to improve the performances and were achieved by grinding LiMn2O4 and Li2O at 700 rpm for 10 h under an argon atmosphere. The product shows a high initial discharge capacity of 287.9 mAh g–1 at 0.05 C between 1.2 and 4.6 V and retains 83.2% of the capacity after 50 cycles. The nanoscale interfacial structure was clarified by spherical aberration-corrected microscopy and XRD refinement, and complex occupancies of Li and Mn were found at the interface. A correlation between the interfacial properties and electrochemical performance was established, and the improved performance could be attributed to the polycrystalline nature of the material, the unique Li-rich interfacial structure, and the slightly elevated valence state of Mn. The present results may provide insight for further evaluating the complex mechanism of controlling the electrochemical performance of LiMn2O4

Tuning the Nanoarea Interfacial Properties for the Improved Performance of Li-Rich Polycrystalline Li-Mn‑O Spinel

The nontoxicity and low cost make LiMn2O4 a competitive cathode material for lithium-ion batteries. LiMn2O4 has a high theoretical capacity (296 mAh g–1) when cycled in the 3 and 4 V regions. However, it displays a low practical capacity (∼120 mAh g–1) because of the unavailability of the 3 V region caused by severe Jahn–Teller distortion. The present work investigated the full utilization of LiMn2O4 in both 3 and 4 V by tuning the nanoscale interfacial properties. Li-rich structures at the surface and interface of the spinel material and nanograin strain were introduced to improve the performances and were achieved by grinding LiMn2O4 and Li2O at 700 rpm for 10 h under an argon atmosphere. The product shows a high initial discharge capacity of 287.9 mAh g–1 at 0.05 C between 1.2 and 4.6 V and retains 83.2% of the capacity after 50 cycles. The nanoscale interfacial structure was clarified by spherical aberration-corrected microscopy and XRD refinement, and complex occupancies of Li and Mn were found at the interface. A correlation between the interfacial properties and electrochemical performance was established, and the improved performance could be attributed to the polycrystalline nature of the material, the unique Li-rich interfacial structure, and the slightly elevated valence state of Mn. The present results may provide insight for further evaluating the complex mechanism of controlling the electrochemical performance of LiMn2O4

Surfactant Induced Crystal Regulation and Dual Layer Carbon Coating Formation for Enhanced Performance of High Voltage Olivine-Type Lithium Cobalt Phosphate Cathode Materials

In recent years, the rapid development of new electric vehicles has ushered in a golden age of lithium-ion battery research. In this research, surfactant induced carbon-decorated nanoplates LiCoPO4 were successfully prepared using a combination of solvothermal treatment and the carbonization process. The results show that the incorporation of cetyltrimethyl­ammonium bromide (CTAB) surfactant presents dual influences on the preparation process of LiCoPO4 cathode materials. The first one is that CTAB could introduce micelles into the hydrothermal synthesis system to facilitate the reduction of grain size, therefore shortening the lithium-ion transmission path. Another is a unique carbon coating with dual layer structure that was formed during a sintering process due to the presence of a carbon substance derived from CTAB in the solvothermal treatment, resulting in nitrogen doping in the carbon layer and the formation of Co–N bonds on the surface. After optimization of the preparation, LiCoPO4 with the incorporation of 0.2 mmol of CTAB exhibited a high lithium-ion diffusion coefficient of 5.99 × 10–14 cm2 s–1 and an initial specific capacity of 120.1 mAh g–1 at 1 C, and its capacity retention ratio was 84.6% after 400 cycles. Furthermore, this material also delivered an initial specific capacity of 113.0 mAh g–1 at a high current rate of 5 C. The preparation method of materials presented here offers a promising strategy to enhance the feasibility of industrial application for high voltage olivine LiCoPO4

Improved Electrochemical Performance of Spinel LiNi_0.5Mn_1.5O₄ Cathode Materials with a Dual Structure Triggered by LiF at Low Calcination Temperature

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO), which has the advantages of high energy density, low cost, environmental friendliness, and being cobalt-free, is considered one of the most promising cathode materials for the next generation of power lithium-ion batteries. However, the side reaction at the interface between the LNMO cathode material and electrolyte usually causes a low specific capacity, poor rate, and poor cycling performance. In this work, we propose a facilitated method to build a well-tuned dual structure of LiF coating and F– doping LNMO cathode material via simple calcination of LNMO with LiF at low temperatures. The experimental results and DFT analysis demonstrated that the powerful interface protection due to the LiF coating and the higher lithium diffusion coefficient caused by F– doping effectively improved the electrochemical performance of LNMO. The optimized LNMO-1.3LiF cathode material presents a high discharge capacity of 140.3 mA h g–1 at 1 C and 118.7 mA h g–1 at 10 C. Furthermore, the capacity is retained at 75.4% after the 1000th cycle at 1 C. Our research provides a concrete guidance on how to effectively boost the electrochemical performance of LNMO cathode materials

Flexible Organic–Inorganic Composite Solid Electrolyte with Asymmetric Structure for Room Temperature Solid-State Li-Ion Batteries

Solid state electrolytes have stimulated research interest due to their promising application in lithium batteries with high safety. In this paper, an asymmetrical structure composite solid electrolyte consisting of Li1.3Al0.3Ti1.7(PO4)3 (LATP), poly­(vinylidene fluoride–hexafluoropropylene) (P­(VDF-HFP)), succinonitrile (SN), and a polyimide (PI) film (named ACSE-PI) was fabricated successfully. This solid electrolyte is flexible and can be stable at a high temperature of 150 °C. Moreover, it exhibits a wide electrochemical window of 5 V and high ionic conductivity of over 10–4 S cm–1. An all-solid-state battery assembled with this electrolyte exhibits excellent performance at ambient temperature. In particular, the specific discharge capacity of LiFePO4/ACSE-PI/Li battery is 168.4, 164.4, 154.9, 143.4, 129.5, and 109.4 mAh g–1 at a rate of 0.1, 0.2, 0.5, 1, 2, and 5 C, respectively. It also delivers a reversible discharge capacity of 156 mAh g–1 after 200 cycles at 0.2 C. Notably, the battery can also operate at 4 °C, and the discharge capacity is higher than 110 mAh g–1 after 200 cycles at 0.2 C. Considering the good performances mentioned above, the ACSE-PI electrolyte is appropriate for the practical application of a solid-state Li-ion battery with higher safety

Flexible Organic–Inorganic Composite Solid Electrolyte with Asymmetric Structure for Room Temperature Solid-State Li-Ion Batteries

Solid state electrolytes have stimulated research interest due to their promising application in lithium batteries with high safety. In this paper, an asymmetrical structure composite solid electrolyte consisting of Li1.3Al0.3Ti1.7(PO4)3 (LATP), poly­(vinylidene fluoride–hexafluoropropylene) (P­(VDF-HFP)), succinonitrile (SN), and a polyimide (PI) film (named ACSE-PI) was fabricated successfully. This solid electrolyte is flexible and can be stable at a high temperature of 150 °C. Moreover, it exhibits a wide electrochemical window of 5 V and high ionic conductivity of over 10–4 S cm–1. An all-solid-state battery assembled with this electrolyte exhibits excellent performance at ambient temperature. In particular, the specific discharge capacity of LiFePO4/ACSE-PI/Li battery is 168.4, 164.4, 154.9, 143.4, 129.5, and 109.4 mAh g–1 at a rate of 0.1, 0.2, 0.5, 1, 2, and 5 C, respectively. It also delivers a reversible discharge capacity of 156 mAh g–1 after 200 cycles at 0.2 C. Notably, the battery can also operate at 4 °C, and the discharge capacity is higher than 110 mAh g–1 after 200 cycles at 0.2 C. Considering the good performances mentioned above, the ACSE-PI electrolyte is appropriate for the practical application of a solid-state Li-ion battery with higher safety

Enhanced Rate Performance of Al-Doped Li-Rich Layered Cathode Material via Nucleation and Post-solvothermal Method

Al-doped layered cathode materials Li_{1.5–<i>x</i>}Al_<i>x</i>Mn_0.675Ni_0.1675Co_0.1675O₂ have been successfully synthesized via a rapid nucleation and post-solvothermal method. The surface morphology and crystal structures of Al-doped Li-rich materials are investigated via scanning electron microscopy, X-ray diffraction, Raman spectra, and X-ray photoelectron spectroscopy. After optimization, the Li_1.45Al_0.05Mn_0.675Ni_0.1675Co_0.1675O₂ (Al = 0.05) sample showed excellent electrochemical performance, and the discharge capacities are 323.7 and 120 mAh g^–1 at a rate of 0.1 and 20 C, respectively. These improvements, based on electrochemical performance evaluation and density functional theory calculations, might be ascribed to the increased electron conductivity of layered Li-rich material via Al³⁺ ions doped into a crystal structure