Nutshell to ultra-high energy density fluorocarbon cathode material

Fluorocarbon (CFx) materials have become one of the hot spots in the research of high-tech, high-performance and cost-effective new carbon-based materials because of their unique physical and chemical properties. Fluorocarbon materials have important application value in many fields, such as the positive electrode of high energy lithium primary batteries, solid lubricants and neutron moderators in nuclear reactors, etc., among which the positive electrode material of high energy lithium batteries is the most demanded field at present. Lithium primary batteries have become the primary power source for long-term, durable, high-capacity energy products such as artificial pacemakers, RFID devices, remote keyless systems, and portable instruments. In addition, they can be used as a supplementary energy source for rechargeable lithium-ion batteries when their charge is low. Lithium-fluorocarbon (Li-CFx) battery can be made into a new type of battery with high energy density, high output power, long storage period and high safety performance. It has the unique advantages of large specific energy, wide temperature range (-40℃-80℃), small self-discharge rate, stable operating voltage, etc., making it an important cathode material for energy storage batteries. However, the incompatibility between the high degree of fluorination and the electrochemical activity of C-F bond limits the further improvement of the energy density of CFC cathode materials.
      Recently, Professor Feng Wei's team from the School of Materials Science and Engineering of Tianjin University (FOCC Laboratory) has developed a lithium/fluorocarbon battery cathode material prepared by low temperature fluorination using biomass carbon as the original material. Compared with traditional carbonaceous materials and specific lattice constants as starting materials, a series of fluorocarbon materials (abbreviated F-cMNS) were prepared by using amorphous calcined Macadamia nut shells as starting materials and fluorinated with pure F2 gas at low temperature. The prepared F-cMNS have high specific capacity and high discharge voltage, and the maximum energy density is 2585 Wh kg-1, which is much higher than that of industrial fluorinated fossil inks and other fluorinated nanostructured carbons. Subsequently, the soft pack battery of the material has been verified, and the soft pack battery has good electrochemical performance. Unlike expensive, low-yield nanocarbons, the availability and low cost of macadamia shells supports the large-scale production of F-cMNS. Therefore, F-cMNS has the potential to replace industrial fluorinated fossil inks and may promote the development of high-performance lithium primary batteries. The technology has been applied for Chinese invention patent (patent No. : 201811026672.4).

FIG. 1 SEM and TEM images of (a,e) F-CMNS-220, (b, F) F-CMNS-250, (c,g) F-CMNS-280, and (d,h) F-CMNS-300

FIG. 2 Electrochemical performance of F-cMNS at 10 mA g−1 discharge

FIG. 3 Electrochemical performance of the soft-pack battery prepared with F-cMNS-280 as the positive electrode material at 0.01C discharge. The picture shows a digital photo of a Li/CFx battery with a capacity of 1Ah.