Insights into the role of Li2FeP2O7 phase in LiFePO4/C composite cathode

• Published in: Ionics Vol. 28; no. 11; pp. 5059 - 5069
• Main Authors: Lan, Jian, Hou, Hongying, Yu, Xiaohua, Rong, Ju, Huang, Baoxiang
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.11.2022
• Subjects: Chemistry; Chemistry and Materials Science; Condensed Matter Physics; Electrochemistry; Energy Storage; Optical and Electronic Materials; Original Paper; Renewable and Green Energy; FeP; Lithium ion battery; LiFePO; Circular economy; Double carbon goals; Li-storage mechanism; C composite cathode; Li; O
• ISSN: 0947-7047; 1862-0760
• DOI: 10.1007/s11581-022-04760-8

With the rapid development of the social economy, various wastes continuously increase and accumulate, which are generally subject to the landfills or incineration. More desirably, they should be changed into the useful materials for the low environment emission. Herein, one smart design with three goals was performed by high-temperature solid-state reaction in N 2 atmosphere: the in situ combination of Li 2 FeP 2 O 7 and LiFePO 4 /C was achieved, carbon coating was performed, and two wastes (expired ferrous gluconate and spent Li foils) were recycled as the raw materials. Furthermore, the content of Li 2 FeP 2 O 7 in the composite cathode could be tuned by tailoring the feed ratio of ferrous oxalate and expired ferrous gluconate. The resultant samples were marked as L 2 FP 2 /LFP/C-1, L 2 FP 2 /LFP/C-2 and L 2 FP 2 /LFP/C-3, and the corresponding contents of Li 2 FeP 2 O 7 phase were about 4.1 wt%, 3.0 wt%, and 2.0 wt%, respectively. The results showed that L 2 FP 2 /LFP/C-2 cathode delivered the best electrochemical performances due to the joint contributions and synergistic effect of optimal Li 2 FeP 2 O 7 phase and carbon layer. For example, the reversible specific discharge capacity was 135.0 mAh/g at 1.0 C for 500 cycles, higher than 123.1 mAh/g of L 2 FP 2 /LFP/C-1 cathode and 113.4 mAh/g of L 2 FP 2 /LFP/C-3 cathode. Especially, the Li-storage mechanism of Li 2 FeP 2 O 7 phase was also disclosed for the first time. Obviously, such efforts could promote the achievement of the circular economy and low environment emission.