High-Performance Single-Crystal Lithium-Rich Layered Oxides Cathode Materials via Na2WO4-Assisted Sintering.

Single-crystal lithium-rich layered oxides (LLOs) with excellent mechanical properties can enhance their crystal structure stability. However, the conventional methods for preparing single-crystal LLOs, require large amounts of molten salt additives, involve complicated washing steps, and increase the difficulty of large-scale production. In this study, a sodium tungstate (Na2WO4)-assisted sintering method is proposed to fabricate high-performance single-crystal LLOs cathode materials without large amounts of additives and additional washing steps. During the sintering process, Na2WO4 promotes particle growth and forms a protective coating on the surface of LLOs particles, effectively suppressing the side reactions at the cathode/electrolyte interface. Additionally, trace amounts of Na and W atoms are doped into the LLOs lattice via gradient doping. Experimental results and theoretical calculations indicate that Na and W doping stabilizes the crystal structure and enhances the Li+ ions diffusion rate. The prepared single-crystal LLOs exhibit outstanding capacity retention of 82.7% (compared to 65.0%, after 200 cycles at 1 C) and a low voltage decay rate of 0.76 mV per cycle (compared to 1.80 mV per cycle). This strategy provides a novel pathway for designing the next-generation high-performance cathode materials for Lithium-ion batteries (LIBs).

Anion-Cation Dual-Ion Multisite Doping Stabilizes the Crystal Structure of Li-Rich Layered Oxides.

Li-rich layered oxide (LLOs) cathode materials are gaining increasing attention as lithium-ion batteries (LIBs) pursue greater energy density. However, LLOs still suffer from severe capacity fading and voltage decay due to their unstable crystal structure. Hence, the anion-cation dual-ion multisite doping strategy based on Mg and S atoms is used to stabilize the crystal structures of LLOs. Mg substitutes Li atoms in the Li and transition-metal (TM) layers, while S atoms occupy tetrahedral interstitial sites and lattice O sites, all of which contribute to the crystal structure stability of LLOs. Theoretical calculations show that Mg/S dual-ion multisite doping successfully reduces the energy levels of the TM 3d-O 2p and isolated O 2p orbitals, which effectively stabilizes the lattice oxygen. Therefore, multisite-doped samples exhibit promising electrochemical performance. This strategy provides a new approach to enhance the crystal structure stability of LLOs for the design of high-energy-density Li-ion batteries.

LiNO3-Assisted Succinonitrile-Based Solid-State Electrolyte for Long Cycle Life toward a Li-Metal Anode via an In Situ Thermal Polymerization Method.

Succinonitrile (SN)-based electrolytes have a great potential for the practical application of all-solid-state lithium-metal batteries (ASSLMBs) due to their high room-temperature ionic conductivity, broad electrochemical window, and favorable thermal stability. Nevertheless, the poor mechanical strength and low stability toward Li metal hinder the further application of SN-based electrolytes to ASSLMBs. In this work, the LiNO3-assisted SN-based electrolytes are synthesized via an in situ thermal polymerization method. With this method, the mechanical problem is negligible, and the stability of the electrolyte enhances tremendously toward Li metal due to the addition of LiNO3. The LiNO3-assisted electrolytes exhibit a high ionic conductivity of 1.4 mS cm-1 at 25 °C, a wide electrochemical window (0-4.5 V vs Li+/Li), and excellent interfacial compatibility with Li (stable for over 2000 h at a current density of 0.1 mA cm-1). The LiFePO4/Li cells with the LiNO3-assisted electrolytes present significantly enhanced rate capability and cycling performance compared to the control group. NCM622/Li batteries also exhibit good cycling and rate performances with a voltage range of 3.0 to 4.4 V. Furthermore, ex situ SEM and XPS are employed. A compact interface is observed on Li anode after cycling, and the polymerization of SN is found to be suppressed. This paper will promote the development of practical application of SN-based ASSLMBs.

Dual-Site Doping Strategy for Enhancing the Structural Stability of Lithium-Rich Layered Oxides.

Lithium-rich layered oxide (LLO) cathode materials are considered to be one of the most promising next-generation candidates of cathode materials for lithium-ion batteries due to their high specific capacity. However, some inherent defects of LLOs hinder their practical application due to the oxygen loss and structure collapse resulting from intrinsic anion and cation redox reactions, such as poor cycle stability, sluggish Li+ kinetics, and voltage decay. Herein, we put forward a facile synergistic strategy to respond to these shortcomings of LLOs via dual-site doping with cerium (Ce) and boron (B) ions. The doped Ce ions occupy the octahedral sites, which not only enlarge the cell volume but also stabilize the layered framework and introduce abundant oxygen vacancies for LLOs, while B ions occupy the tetrahedral sites in the lattice, which block the migration path of transition metal (TM) ions and reduce the oxygen loss using the strong B-O bond. Based on this dual-site doping effect, after 100 cycles at 1 C, the dual-site doped materials exhibit excellent structural stability with a capacity retention of 91.15% (vs 75.12%) and also greatly suppress the voltage decay in LLOs with a voltage retention of 93.60% (vs 87.83%).

[Determination of trace elements in the edible fungi by inductively coupled plasma atomic emission spectrometry].

In the present paper, samples were digested by high pressure digestion pots, reducing the loss of trace elements during the digestion process. The contents of trace elements in edible fungi such as Ca, Na, K, Mg, Mn, Ba, Fe, Co, Ge and Cu were determined by inductively coupled plasma atomic emission spectrometry. The relative standard deviation with high pressure digestion pots was 0.160-2.860, and that with wet method was 0.33%-3.49%, so it could be seen that the measurement precisions of the two methods were good, and the former was better. The measurement results with the two methods were checked by t-test, and the values in the range of 0.002 4-2.473 were lower than t(0.99, 9) (3.25). The measurement results showed that the two methods had no obvious differences, namely no system errors occurred. The recovery rates with high pressure digestion pots were in the range of 96.6% -103%. The method of high pressure digestion pots was suitable for the determination of trace elements in edible fungi with the advantages of being simple, rapid, sensitive, stable and accurate etc., and the results were satisfactory.