WANG Shangming, XIAO Liwen

(Trinity College Dublin, Dublin 999015, Ireland)

Extended abstract:[Significance] Lithium-ion batteries (LIBs) have emerged as the cornerstone of modern energy technologies, extensively applied in energy storage systems and electric vehicles (EVs). However, the widespread application of LIBs faces critical technical barriers, particularly concerning key electrode materials, such as lithium iron phosphate (LiFePO₄), which is hindered by poor electronic conductivity and slow charging rates. Traditional high-temperature solid-state synthesis, typically operating at temperatures of ≥700 ℃, faces challenges in precisely controlling material microstructures and particle size, thus limiting electrochemical performance. In contrast, low-temperature synthesis methods have gained attention, due to their capability for precise structural control, significantly reduced energy consumption and environmentally friendly characteristics, paving the way for next-generation electrode materials.[Progress] Low-temperature synthesis approaches primarily include hydrothermal, solvothermal and ionothermal methods, each exhibiting distinctive advantages and limitations. Hydrothermal synthesis, conducted in sealed environments using water as a reaction medium, offers excellent control over particle size (typically in the range of 50–200 nm), significantly shorter lithium-ion diffusion paths, and lower charge transfer impedance compared to traditional methods. For instance, LiFePO₄/carbon/graphene composites synthesized hydrothermally by Liu et al. (2023) demonstrated enhanced conductivity and cycle stability. Solvothermal methods, employing organic solvents, provide flexibility in reaction conditions and materials design. For example, solvothermally synthesized LiFePO₄@CNT and LiFePO₄/graphene composite materials exhibit capacities exceeding 130 mAh·g⁻¹, representing 10–20% improvement over the traditional high-temperature methods. Additionally, these materials maintain over 95% capacity retention after 100 charge-discharge cycles, largely attributed to their advanced three-dimensional conductive network structures. Ionothermal synthesis, utilizing ionic liquids or deep eutectic solvents as the reaction media, emerges as an innovative approach capable of further optimizing surface conductive interface structures. The unique ionic environment created during synthesis notably reduces interface resistance by approximately 30%, substantially enhancing rate capability and long-term cycling stability. Recent studies highlight ionic liquids' roles not merely as solvents but as molecular templates, facilitating controlled particle growth and surface structure optimization, thus significantly improving electrochemical properties.[Conclusions and prospects] The low-temperature synthesis methods were systematically reviewed, significantly enhance electrochemical performance in lithium-based electrode materials through precise microstructural and interface control, with following specific aspects.(1) Low-temperature synthesis reduces reaction temperatures from about 700 ℃ in traditional solid-state methods to about 250 ℃, achieving more than 60% reduction in energy consumption.(2) Precise microstructural control achieved through hydrothermal synthesis produces particle sizes typically below 200 nm, significantly improving lithium-ion diffusion rates and reducing interface impedance.(3) Solvothermally synthesized composites exhibit improved capacities (>130 mAh·g⁻¹) and stability, with capacity retention exceeding 95% after extensive cycling.(4) Ionothermal methods leveraging ionic liquids enable precise interface structuring, further reducing charge transfer resistance by about 30%, thereby enhancing the rate capability and cycle longevity.Despite these significant advances, scaling low-temperature synthesis to industrial levels faces challenges, including notably longer reaction times (typically 12–24 hours) and higher equipment costs. The adoption of continuous-flow reactors or microwave-assisted synthesis technologies promises a reaction time reduction of more than 50%, facilitating industrial-scale application.Overall, these research avenues will significantly contribute to the practical realization of low-temperature synthesis technologies in the sustainable production of high-performance lithium-ion battery electrode materials.

Key words: lithium-ion battery; low-temperature synthesis method; electrode material; ion thermal method; electrochemical performancer