Biochar-enhanced three-dimensional conductive network thick electrodes for efficient lithium extraction from salt lake brines with high Magnesia-lithium ratios.

Enhancing the kinetic performance of thick electrodes is essential for improving the efficiency of lithium extraction processes. Biochar, known for its affordability and unique three-dimensional (3D) structure, is utilized across various applications. In this study, we developed a biochar-based, 3D-conductive network thick electrode (∼20 mg cm-2) by in-situ deposition of LiFePO4 (LFP) onto watermelon peel biomass (WB). Utilizing Density Functional Theory (DFT) calculations complemented by experimental data, we confirmed that this The thick electrode exhibits outstanding kinetic properties and a high capacity for lithium intercalation in brines, even in environments where the Magnesia-lithium ratios are significantly high. The electrode showed an impressive intercalation capacity of 30.67 mg g-1 within 10 min in a pure lithium solution. It also maintained high intercalation performance (31.17 mg g-1) in simulated brines with high Magnesia-lithium ratios. Moreover, in actual brine, it demonstrated a significant extraction capacity (23.87 mg g-1), effectively lowering the Magnesia-lithium ratio from 65 to 0.50. This breakthrough in high-conductivity thick electrode design offers new perspectives for lithium extraction technologies.

Enhanced Cathode Performance: The Heterostructure Construction of LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12.

In this study, the heterostructure cathode material LiCoO2@Co3O4@Li6.4La3Zr1.4Ta0.6O12 was prepared by coating Li6.4La3Zr1.4Ta0.6O12 on the surface of LiCoO2 through a one-step solid-phase synthesis. The morphology, structure, electrical state, and elemental contents of both pristine and modified materials were assessed through a range of characterization techniques. Theoretical calculations revealed that the LCO@LLZTO material possessed a reduced diffusion barrier compared to LiCoO2, thereby facilitating the movement of Li ions. Electrochemical tests indicated that the capacity retention rate of the modified cathode composites stood at 70.43% following 300 cycles at a 2C rate. This high rate occurred because the Li6.4La3Zr1.4Ta0.6O12 film on the surface enhanced the migration of Li+, and the spinel phase of Co3O4 had better interfacial stability to alleviate the generation of microcracks by inhibiting the phase change from the layered phase to the rock-salt phase, which considerably improved the electrochemical properties.

Understanding Electrochemical Performance Enhancement with Quaternary NCMA Cathode Materials.

Ni-rich cathode materials show promise for use in lithium-ion batteries. However, a significant obstacle to their widespread adoption is the structural damage caused by microcracks. This research paper presents the synthesis of Ni-rich cathode materials, including LiNi0.8Co0.1Mn0.1O2 (referred to as NCM) and Li(Ni0.8Co0.1Mn0.1)0.98Al0.02O2 (referred to as NCMA), achieved through the high-temperature solid-phase method. Electrochemical (EC) testing results reveal the impressive EC performance of NCMA. NCMA exhibited a discharge capacity of 141.6 mAh g-1 and maintained a cycle retention rate of up to 74.92% after 300 cycles at a 1 C rate. In contrast, the NCM had a discharge capacity of 109.7 mAh g-1 and a cycle retention rate of 61.22%. Atomic force microscopy showed that the Derjaguin-Muller-Toporov (DMT) modulus value of NCMA exceeded that of NCM, signifying a greater mechanical strength of NCMA. Density functional theory calculations demonstrated that the addition of aluminum during the delithiation process led to the mitigation of anisotropic lattice changes and the stabilization of the NCMA structure. This improvement was attributed to the relatively stronger Al-O bonds compared to the Ni(Co, Mn)-O bonds, which reduced the formation of microcracks by enhancing NCMA's mechanical strength.

Nano ZrO2 Modification for Enhancement of the Electrochemical Performance of Li-Rich Manganese-Based Cathodic Materials.

In this work, high-temperature solid-phase techniques have been used to produce both natural and nano ZrO2-modified Li-rich manganese-based cathodic materials. Several characterizations were carried out to evaluate the morphology, structure, electrical state, and elemental content of unmodified as well as nano-modified Li1.2Ni0.13Co0.13Mn0.54O2. The results of electrochemical tests showed that cathodic materials modified with 0.02 mol nano ZrO2 performed extremely well electrochemically, with initial discharge capacity and coulombic efficiency at 0.1 C reaching up to 308.5 mAh g-1 and 95.38%, respectively. After 170 cycles at 0.2 C, a magnitude of 200.2 mAh g-1 for the final discharge capacity was attained, which translates to a capacity retention of 68.68%. Calculations using density functional theory (DFT) show that adding nanoscale ZrO2 speeds up Li-ion diffusion and increases conductivity by lowering the barrier energy for the migration of Li ions. The structural layout of Li-rich manganese-based cathodic materials may therefore be clarified by the proposed modification technique for nano ZrO2.

New Insight into the Working Mechanism of Lithium-Sulfur Batteries under a Wide Temperature Range.

Sweet potato-derived carbon with a unique solid core/porous layer core/shell structure is used as a conductive substrate for gradually immobilizing sulfur to construct a cathode for Li-S batteries. The first discharge specific capacity of the Li-S batteries with the C-10K@2S composite cathode at 0.1C is around 1645 mAh g-1, which is very close to the theoretical specific capacity of active sulfur. Especially, after 175 cycles at 0.5C, the maintained specific discharge capacities of the C-10K@2S cathode at -20, 0, 25, and 40 °C are about 184.9, 687.2, 795.5, and 758.3 mAh g-1, respectively, and the cathode is superior to most of the classical carbon form matrices. Working mechanisms of the cathodes under different temperatures are confirmed based on X-ray photoelectron spectroscopy (XPS) and in situ X-ray diffraction (XRD) characterizations. Distinctively, during the discharge stage, the widely proposed two-step cathodic reactions occur simultaneously rather than sequentially. In addition, the largely accelerated phase conversion efficiency of the cathode at a higher temperature (from room temperature to 40 °C) contributes to its enhanced charge/discharge specific capacity, while the byproduct Li2S2O7 or Li3N irreversibly formed during the cycles limits its application performance at 0 °C. These conclusions would be very significant and useful for designing cathodes for Li-S batteries with excellent wide working temperature performance.

Melt-diffusion and ion-exchange methods: self-triggered O-rich groups on the surface of acetylene black using S-EDA solution to boost its sulfur content for lithium-sulfur batteries.

Only a few studies have described the use of H+-attacking S-EDA in nucleophilic substitution reactions to bind frameworks and sulfur in cathode materials, which is also known as the ion-exchange method. The pros and cons of this method are still unclear in relation to lithium-sulfur battery applications. Here, the influences of two synthetic routes, a melt-diffusion method and H+ reacting with S-EDA via nucleophilic substitution, on the morphologies and electrochemical properties of cathode materials are discussed in detail based on in situ XRD and other advanced technologies. Accordingly, high S-loading is achieved when H+ reacts with S-EDA via ion exchange on the surface of acetylene black, and capacities of 693.8, 644.5, and 638.9 mA h g-1 are obtained over the first three cycles when the C/S composite is used as a cathode in coin cells without the conductive additive Super P. In situ XRD data confirm that poor electrochemical properties can mainly be attributed to the conversion rate of S species being too rapid to thoroughly utilize the S molecules that are immobilized, which means that more fixed sulfur can form during the charge/discharge process when using the ion-exchange method to make the C/S composite. In addition, a long-chain polysulfide shuttling effect is directly noticed via AFM in tapping-KPFM mode in the C/S composite that was synthesized via the melt-diffusion method, even though polar S-O bonds exist in the composite. The increase in the cathodic surface potential from 102.8 to 141.1 mV and the increase in the morphological height from 547.7 to 829.7 nm during the discharge/charge process can be attributed to the process of S loss.

Enhanced Cathode Performance: Mixed Al2O3 and LiAlO2 Coating of Li1.2Ni0.13Co0.13Mn0.54O2.

Li-rich, manganese-based cathode materials are attractive candidates for Li-ion batteries because of their excellent capacity, but poor rate and cycle performance have limited their commercial applications. Herein, Li-rich, manganese-based cathode materials were modified with aluminum isopropoxide as an aluminum source modifier using a sol-gel technique followed by a wet chemical method. To investigate the structure, morphology, electronic state, and elemental composition of both pristine- and surface-modified Li1.2Ni0.13Co0.13Mn0.54O2, various characterizations were performed. Based on density functional theory simulations and the results of electrochemical tests, the surface of the modified cathode material was found to contain at least part of the LiAlO2 phase. This was attributed to the aluminum isopropoxide reacting with a Li2CO3/LiOH byproduct on the material surface to form LiAlO2 with a three-dimensional Li-ion channel structure. Electrochemical testing revealed that a 3 wt % aluminum isopropoxide coating of cathode materials exhibited excellent electrochemical performance. Furthermore, the initial Coulombic efficiency and discharge capacity at 0.1 C were up to 88.55% and 272.7 mAh g-1, respectively. A final discharge capacity of 186.4 mAh g-1 was achieved, corresponding to a capacity retention of 83.55% after 300 cycles at 0.5 C. This was attributed to LiAlO2 partially accelerating the diffusion of Li ions and Al2O3 aiding the avoidance of side reactions in the mixed coating layer by partially protecting the structure.

Evidence for the influence of polaron delocalization on the electrical transport in LiNi0.4+xMn0.4-xCo0.2O2.

Polaron delocalization in layered transition-metal oxides can considerably impact their physical properties and technological applications. Herein, we present the evidence for the influence of polaron delocalization on the electrical transport of layered oxides LiNi0.4+xMn0.4-xCo0.2O2, an active cathode material, by controlling the chemical compositions. We find that the chemical composition at x = 0.3 exhibits a sharp increment in electronic conductivity of four orders of magnitude at room temperature with respect to that at x = 0. We attribute the increased electronic conductivity to a low hopping energy in addition to a weak electron-phonon interaction. The weakened electron-phonon interaction is the source of polaron delocalization in LiNi0.4+xMn0.4-xCo0.2O2, which became improved with increasing x due to the increased polaron sizes. Moreover, it is also suggested that the polaron delocalization may have a relationship with the strong Jahn-Teller distortion induced by Ni3+. The analysis of temperature dependent electrical transport within the framework of the small polaron hopping conduction model enables us to comprehend the influence of polaron delocalization on the electrical transport pertinent to the applications of layered oxide materials.