Halankar Kruti K, Mandal B P, Jangid Manoj K, Mukhopadhyay A, Meena Sher Singh, Acharya R, Tyagi A K
Chemistry Division, Bhabha Atomic Research Centre Mumbai-400085 India
Homi Bhabha National Institute Mumbai-400085 India.
RSC Adv. 2018 Jan 3;8(2):1140-1147. doi: 10.1039/c7ra10112k. eCollection 2018 Jan 2.
Carbon coated Li FePO samples with systematically varying Li-content ( = 1, 1.02, 1.05, 1.10) have been synthesized a sol-gel route. The Li : Fe ratios for the as-synthesized samples is found to vary from ∼0.96 : 1 to 1.16 : 1 as determined by the proton induced gamma emission (PIGE) technique (for Li) and ICP-OES (for Fe). According to Mössbauer spectroscopy, sample LiFePO has the highest content (, ∼91.5%) of the actual electroactive phase (, crystalline LiFePO), followed by samples LiFePO, LiFePO and LiFePO; with the remaining content being primarily Fe-containing impurities, including a conducting FeP phase in samples LiFePO and LiFePO. Electrodes based on sample LiFePO show the best electrochemical performance in all aspects, retaining ∼150 mA h g after 100 charge/discharge cycles at C/2, followed by sample LiFePO (∼140 mA h g), LiFePO (∼120 mA h g) and LiFePO (∼115 mA h g). Furthermore, the electrodes based on sample LiFePO retain ∼107 mA h g even at a high current density of 5C. Impedance spectra indicate that electrodes based on sample LiFePO possess the least charge transfer resistance, plausibly having influence from the compositional aspects. This low charge transfer resistance is partially responsible for the superior electrochemical behavior of that specific composition.
通过溶胶 - 凝胶法合成了锂含量系统变化（(x = 1, 1.02, 1.05, 1.10)）的碳包覆磷酸铁锂（LiFePO）样品。通过质子诱导γ发射（PIGE）技术（用于锂）和电感耦合等离子体发射光谱法（ICP - OES）（用于铁）测定，合成样品的锂铁比在约(0.96:1)至(1.16:1)之间变化。根据穆斯堡尔光谱，LiFePO样品中实际电活性相（结晶LiFePO）的含量最高（约(91.5%)），其次是LiFePO、LiFePO和LiFePO样品；其余含量主要是含铁杂质，包括LiFePO和LiFePO样品中的导电FeP相。基于LiFePO样品的电极在各方面均表现出最佳的电化学性能，在(C/2)下进行100次充放电循环后保持约(150 mA h g^{-1})，其次是LiFePO样品（约(140 mA h g^{-1})）、LiFePO样品（约(120 mA h g^{-1})）和LiFePO样品（约(115 mA h g^{-1})）。此外，基于LiFePO样品的电极即使在(5C)的高电流密度下仍保持约(107 mA h g^{-1})。阻抗谱表明，基于LiFePO样品的电极具有最小的电荷转移电阻，这可能受到成分方面的影响。这种低电荷转移电阻部分归因于该特定组成的优异电化学行为。
