Toward the High‐Performance Lithium Primary Batteries by Chemically Modified Fluorinate Carbon with δ‐MnO₂

Abstract

Li/CFx battery is one of the most promising lithium primary batteries (LPBs) which yields the highest energy density but with poor rate capability. This Achilles'’ heel hinders the large‐scale applications of Li/CFx batteries. This work first reports a facile chemical modification method of CFx with δ‐MnO2. Having benefited from the chemical bonding, the electrochemical performance at high‐rate discharge is remarkably enhanced without compromising the specific capacity. The coin cells exhibit an energy density of 1.94 × 103 Wh kg−1 at 0.2 C, which is approaching the theoretical energy density of commercial fluorinated graphite (2.07 × 103 Wh kg−1). A power density of 5.49 × 104 W kg−1 at 40 C associated with an energy density of 4.39 × 102 Wh kg−1, which is among the highest value of Li/CFx batteries, are obtained. Besides, the punch batteries achieve an ultrahigh power density of 4.39 × 104 W kg−1 with an energy density of 7.60 × 102 Wh kg−1 at 30 C. The intrinsic reasons for this outstanding electrochemical performance, which are known as the fast Li+ diffusion kinetics guided by thin δ‐MnO2 flakes and the low formation energy barrier caused by chemical bonding, are explored by the galvanostatic intermittent titration technique (GITT) and theoretical calculations.

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

“…The 19 F spectra of the fluorinated CNFs before and after milling are shown in Figure 4c. Whatever the sample, the fine peak centered at −187 ppm is assigned to the covalent C-F bonds.…”

“…The 19 F and 13 C solid-state NMR experiments were performed using a 300 MHz Bruker Avance spectrometer at room temperature. A cross-polarization (CP)/magic-angle spinning (MAS) NMR probe operating with 2.5 mm and 4 mm rotors was used at 30 kHz and 10 kHz spinning rates for the 19 F and 13 C measurements, respectively. A probe (Bruker) with fluorine decoupling on a 4 mm rotor was used.…”

“…A probe (Bruker) with fluorine decoupling on a 4 mm rotor was used. For the MAS spectra, a simple sequence was performed with a single π/2 pulse length of 4.0 and 3.5 µs for 19 F and 13 C, respectively. The 13 C NMR was performed at a frequency of 73.4 MHz and tetramethylsilane (TMS) was used as the reference.…”

“…Because fluorinated carbons (CFxs) exhibit the highest theoretical energy density among current cathode materials for lithium primary batteries, extensive efforts are devoted to the enhancement of either their energy density, their power density, or both (see recent review papers [ 1 , 2 , 3 , 4 ]). The very recent strategies involve (i) considering new carbonaceous precursors for fluorination or innovative fluorination routes [ 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ], (ii) chemical changes in the CFx, either on the surface or in the bulk [ 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 ], and (iii) change in the electrolyte composition [ 13 , 23 , 24 , 25 , 26 , 27 , 28 , 29 ]. Ball milling, a simple process for reducing the particle size of a compound, is widely used for electrode materials [ 30 , 31 , 32 , 33 , 34 ], creating more space to accumulate the LiF(s) particles formed.…”

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

“…Compared with previously reported CFx cathodes, the FCNH-160 cathodes in this study showed unprecedented rate capabilities (Figure 6f; Table S3, Supporting Information). [11,15,30,35,[40][41][42][43][44] The relatively poor rate capability of FCNH-160 is attributed to the poor electrical conductivity, which decreases from 1.05 × 10 4 S cm −1 for pristine CNH to 3.57 × 10 −9 S cm −1 after the fluorination process. The drastically reduced electrical conductivity was assigned to the destruction of conjugated structure, revealed by the few remaining sp 2 hybridized C atoms in the XPS spectrum.…”