Fluorinated Carbon Nanohorns as Cathode Materials for Ultra-High Power Li/CFx Batteries

Organic Dinitrates: Electrolyte Additives That Increase the Energy Densities of Lithium/Graphite Fluoride Batteries

Li/graphite fluoride (Li/CFx) batteries display the highest energy densities among those of commercially available primary Li batteries but fail to satisfy the high-performance requirements of advanced applications. To address this drawback, two liquid organic dinitrates, namely, 1,4-butanediol dinitrate (BDE) and 2,2,3,3-tetrafluoro-1,4-butanediol dinitrate (TBD), were employed as high-energy energetic materials, and they were highly compatible with the electrolytes of Li/CFx batteries. The use of Super P electrodes confirmed that the reduction reaction mechanisms of both nitrate ester-based compounds delivered considerable specific capacities, associated with discharge potentials matching that of the Li/CFx battery. When considering the combined mass of the electrolyte and cathode as the active material, the overall energy densities of the Li/CFx batteries increased by 25.3% (TBD) and 20.8% (BDE), reaching 1005.50 and 969.1 Wh/kg, respectively. The superior performance of TBD was due to the synergistic effects of the high electronegativities and levels of steric hindrance of the F atoms. Moreover, the nanocrystal LiF particles generated by TBD induced crack formation within the fluorinated graphite, increasing the lithium-ion accessible surface area and enhancing its utilization efficiency. These combined factors enhanced the reactivity of TBD and facilitated its involvement in electrochemical reactions, thus improving the capacity of the battery. The developed strategy enables the facile, cost-effective enhancement of the capacities of Li/CFx batteries, paving the way for their practical use in energy-demanding devices.

Fluorinated aggregated nanocarbon with high discharge voltage as cathode materials for alkali-metal primary batteries

Due to its exceptionally high theoretical energy density, fluorinated carbon has been recognized as a strong contender for the cathode material in lithium primary batteries particularly valued in aerospace and related industries. However, CF x cathode with high F/C ratio, which enables higher energy density, often suffer from inadequate rate capability and are unable to satisfy escalating demand. Furthermore, their intrinsic low discharge voltage imposes constraints on their applicability. In this study, a novel and high F/C ratio fluorinated carbon nanomaterials (FNC) enriched with semi-ionic C-F bonds is synthesized at a lower fluorination temperature, using aggregated nanocarbon as the precursor. The increased presence semi-ionic C-F bonds of the FNC enhances conductivity, thereby ameliorating ohmic polarization effects during initial discharge. In addition, the spherical shape and aggregated configuration of FNC facilitate the diffusion of Li+ to abundant active sites through continuous paths. Consequently, the FNC exhibits high discharge voltage of 3.15 V at 0.01C and superior rate capability in lithium primary batteries. At a high rate of 20C, power density of 33,694 W kg-1 and energy density of 1,250 Wh kg-1 are achieved. Moreover, FNC also demonstrates notable electrochemical performance in sodium/potassium-CF x primary batteries. This new-type alkali-metal/CF x primary batteries exhibit outstanding rate capability, rendering them with vast potential in high-power applications.

Lithium metal based battery systems with ultra-high energy density beyond 500 W h kg-1

As industries and consumption patterns evolve, new electrical appliances are increasingly playing critical roles in national production, defense, and cognitive exploration. However, the slow development of energy storage devices with ultra-high energy density (beyond 500 W h kg-1) has impeded the promotion and widespread application of the next generation of intelligent, multi-scenario electrical equipment. Among the numerous ultra-high specific energy battery systems, lithium metal batteries (LMBs) hold significant potential for applications in advanced and sophisticated fields. This potential is primarily due to lithium metal's high specific capacity (3860 mA h g-1). However, LMBs face numerous challenges, including the growth of lithium dendrites, poor cycle stability, and safety concerns. In recent years, research on the mechanisms of Li metal-based battery systems, innovation in electrode materials, and optimization of device configurations have made significant progress. In this highlight, we provide a comprehensive overview of the storage mechanisms and the latest advancements in high-energy-density LMBs, represented by systems such as Li-Li1-xMO2, Li-S/Se, Li-gas (CO2/air/O2), Li-CFx, and all-solid-state LMBs. By integrating the current research findings, we highlight the opportunities and future research directions for high-energy-density LMBs, offering new guiding perspectives for their development under practical conditions.

High Energy Density of Ball-Milled Fluorinated Carbon Nanofibers as Cathode in Primary Lithium Batteries

Sub-fluorinated carbon nanofibers (F-CNFs) can be described as a non-fluorinated core surrounded by a fluorocarbon lattice. The core ensures the electron flux in the cathode during the electrochemical discharge in the primary lithium battery, which allows a high-power density to be reached. The ball-milling in an inert gas (Ar) of these F-CNFs adds a second level of conductive sp2 carbons, i.e., a dual sub-fluorination. The opening of the structure changes, from one initially similar multi-walled carbon nanotube to small lamellar nanoparticles after milling. The power densities are improved by the dual sub-fluorination, with values of 9693 W/kg (3192 W/kg for the starting material). Moreover, the over-potential of low depth of discharge, which is typical of covalent CFx, is suppressed thanks to the ball-milling. The energy density is still high during the ball-milling, i.e., 2011 and 2006 Wh/kg for raw and milled F-CNF, respectively.