High-Performance Cr₈O₂₁ Cathode Materials with MnO₂ as an Activator for High-Energy-Density Lithium Primary Batteries

Chromium oxides (Cr 8 O 21 ) have attracted wide application due to their high theoretical capacity and high voltage for lithium primary batteries. However, Cr 8 O 21 is usually prepared by pyrolysis of a CrO 3 precursor and suffers from low capacity and poor rate capability due to the fusion of CrO 3 during the high-temperature reaction process. Herein, MnO 2 was investigated as an activator to study its impact on the electrochemical properties of Cr 8 O 21, which significantly changed with the addition of MnO 2 during the calcination process. With the addition of MnO 2, the discharge capacity and rate capability of the reaction products (Cr 8 O 21 -M) were dramatically improved compared with those of pure Cr 8 O 21 . This improvement is attributed to the superior lithium-ion diffusion kinetics caused by the uniform surface structure and porous features, which reduce the charge transfer resistance. As a result, Cr 8 O 21 -M10 exhibited an excellent discharge specific capacity of 388 mAh g –1 at 0.1C with discharge voltage plateaus of about 3.0 V (vs Li + /Li), reaching an energy density of 1223 Wh kg –1 based on the cathode material. In addition, Cr 8 O 21 -M showed remarkable rate performance, enabling a high-capacity retention of about 70% at 5C. Therefore, it is essential to add an activator agent during the preparation of Cr 8 O 21, which offers a promising avenue for the development of high-energy-density and high-rate-capability Li/Cr 8 O 21 primary batteries.