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The rapid design of advanced materials depends on synthesis parameters and design. A wide range of materials can be synthesized using precursor reactions based on chelated gel and organic polymeric gel pathways. The desire to develop high-performance lithium-ion rechargeable batteries has motivated decades of research on the synthesis of battery active material particles with precise control of composition, phase-purity, and morphology. Among the most common methods reported in the literature to prepare precursors for lithium-ion battery active materials, sol-gel is characterized by simplicity, homogeneous mixing, and tuning of the particle shape. The chelate gel and organic polymeric gel precursor-based sol-gel method is efficient to promote desirable reaction conditions. Both precursor routes are commonly used to synthesize lithium-ion battery cathode active materials from raw materials such as inorganic salts in aqueous solutions or organic solvents. The purpose of this review is to discuss synthesis procedure and summarize the progress that has been made in producing crystalline particles of tunable and complex morphologies by sol-gel synthesis that can be used as active materials for lithium-ion batteries.

A solid-solution cathode of LiCoPO 4 -LiNiPO 4 was investigated as a potential candidate for use with the Li 4 Ti 5 O 12 (LTO) anode in Li-ion batteries. A pre-synthesized nickel-cobalt hydroxide precursor is mixed with lithium and phosphate sources by wet ball milling, which results in the final product, LiNi y Co 1-y PO 4 (LNCP) by subsequent heat treatment. Crystal structure and morphology of the product were analyzed by X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Its XRD patterns show that LNCP is primarily a single-phase compound and has olivine-type XRD patterns similar to its parent compounds, LiCoPO 4 and LiNiPO 4 . Synchrotron X-ray absorption spectroscopy (XAS) analysis, however, indicates that Ni doping in LiCoPO 4 is unfavorable because Ni 2+ is not actively involved in the electrochemical reaction. Consequently, it reduces the charge storage capability of the LNCP cathode. Additionally, ex situ XRD analysis of cycled electrodes confirms the formation of the electrochemically inactive rock salt-type NiO phase. The discharge capacity of the LNCP cathode is entirely associated with the Co 3+ /Co 2+ redox couple. The electrochemical evaluation demonstrated that the LNCP cathode paired with the LTO anode produced a 3.12 V battery with an energy density of 184 Wh kg -1 based on the cathode mass.

We explore a phase engineering strategy to improve the electrochemical performance of transition metal sulfides (TMSs) in anode materials for lithium-ion batteries (LIBs). A one-pot hydrothermal approach has been employed to synthesize MoS 2 nanostructures. MoS 2 and MoO 3 phases can be readily controlled by straightforward calcination in the (200-300) °C temperature range. An optimized temperature of 250 °C yields a phase-engineered MoO 3 @MoS 2 hybrid, while 200 and 300 °C produce single MoS 2 and MoO 3 phases. When tested in LIBs anode, the optimized MoO 3 @MoS 2 hybrid outperforms the pristine MoS 2 and MoO 3 counterparts. With above 99% Coulombic efficiency (CE), the hybrid anode retains its capacity of 564 mAh g -1 after 100 cycles, and maintains a capacity of 278 mAh g -1 at 700 mA g -1 current density. These favorable characteristics are attributed to the formation of MoO 3 passivation surface layer on MoS 2 and reactive interfaces between the two phases, which facilitate the Li-ion insertion/extraction, successively improving MoO 3 @MoS 2 anode performance.