Compound-Hierarchical-Sphere LiNi0.5Co0.2Mn0.3O2: Synthesis, Structure, and Electrochemical Characterization

Challenges and Prospects of Low-Temperature Rechargeable Batteries: Electrolytes, Interfaces, and Electrodes

Rechargeable batteries have been indispensable for various portable devices, electric vehicles, and energy storage stations. The operation of rechargeable batteries at low temperatures has been challenging due to increasing electrolyte viscosity and rising electrode resistance, which lead to sluggish ion transfer and large voltage hysteresis. Advanced electrolyte design and feasible electrode engineering to achieve desirable performance at low temperatures are crucial for the practical application of rechargeable batteries. Herein, the failure mechanism of the batteries at low temperature is discussed in detail from atomic perspectives, and deep insights on the solvent-solvent, solvent-ion, and ion-ion interactions in the electrolytes at low temperatures are provided. The evolution of electrode interfaces is discussed in detail. The electrochemical reactions of the electrodes at low temperatures are elucidated, and the approaches to accelerate the internal ion diffusion kinetics of the electrodes are highlighted. This review aims to deepen the understanding of the working mechanism of low-temperature batteries at the atomic scale to shed light on the future development of low-temperature rechargeable batteries.

High Value-Added Utilization of Waste Hydrodesulfurization Catalysts: Low-Cost Synthesis of Cathode Materials for Lithium-Ion Batteries

This work introduces a one-step method for the preparation of layered oxide cathode materials utilizing pure Ni and Co mixed solution obtained from the waste hydrodesulfurization (HDS) catalyst. An efficient non-separation strategy with pyrometallurgical-hydrometallurgical (pyro-hydrometallurgical) process consisting of roasting and leaching is proposed. Most of the impurity metal elements such as Mo and V were removed by simple water leaching after the waste HDS catalyst was roasted with Na2CO3 at 650 °C for 2.5 h. Additionally, 93.9% Ni and 100.0% Co were recovered by H2SO4 leaching at 90 °C for 2.5 h. Then, LiNi0.533Co0.193Mn0.260V0.003Fe0.007Al0.004O2 (C–NCM) was successfully synthesized by hydroxide co-precipitation and high temperature solid phase methods using the above Ni and Co mixed solution. The final C–NCM material exhibits excellent electrochemical performance with a discharge specific capacity of 199.1 mAh g−1 at 0.1 C and a cycle retention rate of 79.7% after 200 cycles at 1 C. This novel process for the synthesis of cathode material can significantly improve production efficiency and realize the high added-value utilization of metal resources in a waste catalyst.

Preparation of single-crystal ternary cathode materials via recycling spent cathodes for high performance lithium-ion batteries

With the rapid consumption of lithium-ion batteries (LIBs), the recycling of spent LIBs is becoming imperative. However, the development of effective and environmentally friendly methods towards the recycling of spent LIBs, especially waste electrode materials, still remains a great challenge. Herein, on the basis of a Li-based molten salt, we have developed a facile and effective strategy to recycle spent polycrystalline ternary cathode materials into single-crystal cathodes. The regenerated plate-like single-crystal LiNi_0.6Co_0.2Mn_0.2O₂ material with exposed {010} planes achieves an excellent rate performance and outstanding cycling stability. In particular, a high capacity of 155.1 mA h g^-1 and a superior capacity retention of 94.3% can be achieved by the recycled cathode material even after 240 cycles at 1 C. Meanwhile the single-crystal structure can be well reserved without any cracks or pulverization being observed. Moreover, this recycling method can be expanded to recycle other waste Ni-Co-Mn ternary cathode materials (NCM) or their mixtures for producing high-performance single-crystal cathode materials, demonstrating its versatility and flexibility in practical applications. Therefore, the strategy of converting spent NCM cathodes into single-crystal ones with satisfactory electrochemical performance may open up a cost-effective pathway for resolving the issues caused by the large amounts of spent LIBs, thus facilitating the sustainable development of LIBs.

Fast Capacitive Energy Storage and Long Cycle Life in a Deintercalation-Intercalation Cathode Material

Ni-rich Li-ion cathode materials promise high energy density, but are limited in power density and cycle life, resulting from their poor dynamic characteristics and quick degradation. On the other hand, capacitor electrode materials promise high power density and long cycle life but limited capacities. A joint energy storage mechanism of these two kinds is performed in the material-compositional level in this paper. A valence coupling between carbon π-electrons and O^2- is identified in the as-prepared composite material, using a tracking X-ray photoelectron spectroscopy strategy. Besides delivering capacity simultaneously from its LiNi_0.8 Co_0.1 Mn_0.1 O₂ and capacitive carbon components with impressive amount and speed, this material shows robust cycling stability by preventing oxygen emission and phase transformation via the discovered valence coupling effect. Structural evolution of the composite shows a more flattened path compared to that of the pure LiNi_0.8 Co_0.1 Mn_0.1 O₂ , revealed by the in situ X-ray diffraction strategy. Without obvious phase transformation and losing active contents in this composite material, long cycling can be achieved.

La4NiLiO8-Shielded Layered Cathode Materials for Emerging High-Performance Safe Batteries

Low theoretical capacities of the commercial cathode materials (olivine: ∼170 mA h g^-1 and spinel: ∼140 mA h g^-1) dictate the need for higher energy density alternates such as nickel-rich (denotes as NCM) materials with a theoretical capacity of ∼270 mA h g^-1. However, low conductivity and the bulk degradation after direct contact with liquid electrolytes, especially at temperatures higher than 50 °C, are the biggest issues to resolve for safe use and confident commercialization of the NCM materials. In this context, we first report "La₄NiLiO₈ shields" to simultaneously boost charge conduction characteristics and circumvent the electrolytic degradation of NCM. Consequently, the La₄NiLiO₈-shielded LiNi_0.5Co_0.2Mn_0.3O₂ (LSN5) not only offers a 4.1× less charge transfer resistance and significantly higher discharge capacity (219.7 mA h g^-1) than the nonshielded NCM (187 mA h g^-1) and theoretical capacities of commercial cathode materials but also maintains more than 91.7% of capacity retention at 25 °C after 500 cycles and 84.2% at 60 °C after 200 cycles. In contrast, the nonshielded NCM cathodes can only provide 58.9 and 45.5% capacity retentions at corresponding test temperatures and performance cycles. The acquired excellent electrochemical performance and battery stability at both the ambient and high-temperature conductions infer great importance of the novel La₄NiLiO₈ shields in developing high-performance safe secondary batteries.

Controllable Pulse Reverse Electrodeposition of Mesoporous Li xMnO2 Nano/Microstructures with Enhanced Electrochemical Performance for Li-Ion Storage

Given the ever-growing demand of electric vehicles and renewable energies, addressing the poor cyclic stability of lithium manganese dioxide is an urgent challenge. In this study, pulse reverse current as the driving force of a one-pot anodic electrodeposition was exploited to design the physicochemical and electrochemical characteristics of lithium manganese dioxides as cathode materials of Li-ion battery. The pulse reverse parameters, including the span of anodic and cathodic current application ( t_a and t_c) and frequency ( f'), were systematically modulated to determine the optimized values through monitoring the physicochemical properties using X-ray diffraction, thermogravimetric analysis/differential scanning calorimetry, field emission scanning electron microscopy, transmission electron microscopy, energy-dispersive spectrometry, Raman spectroscopy, N₂ adsorption-desorption isotherms, and inductively coupled plasma-optical emission spectroscopy, as well as the electrochemical properties using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge at different currents. Based on the results, Li_0.65MnO₂ synthesized using t_a = 95 ms, t_c = 5 ms, and f' = 8.33 Hz at the constant magnitude of anodic peak current density of 1 mA dm^-2 was determined as the optimized sample. The optimized lithium manganese dioxide rendered superior electrochemical performance with the initial discharge capacity of 283 mAh g^-1, which accounts for 96.4% of the theoretical discharge capacity, preserving 88.3% of this capacity after 300 cycles at 0.1 C and, in the meantime, was able to release a discharge capacity of 115 mAh g^-1 even after cycling at a higher current of 10 C. The superior electrochemical behavior of Li_0.65MnO₂ was attributed to the exclusive hierarchical urchin-like morphology as well as mesoporous nano/microstructures having a notably high Brunauer-Emmett-Teller surface area of 320.12 m² g^-1 alongside mixed-phase α/γ structure owing to the larger 2 × 2 tunnels, which offer more facile Li⁺ diffusion.