Graphite stands out as the most promising anode material for potassium-ion batteries (PIBs) due to its cost-effectiveness and ideal low-potential platform. However, the perceived poor rate capability of graphite has become a key concern for its commercial application in PIBs. Herein, the above understanding on the poor rate capability of graphite is updated. Without modifying graphite structure, by simply introducing a tin trifluoromethanesulfonate (Sn(OTf) 2 ) additive in phosphate-based electrolyte, the graphite in K||graphite half-cell can deliver a capacity of 240 mAh g −1 at a high rate of 2 C (1 C = 279 mA g −1 ) and operates for 1000 cycles with negligible degradation. Moreover, an unprecedented rate capacity of ≈200 mAh g −1 for graphite anode at 4 C is achieved in a three-electrode K|K ref|graphite cell configuration where the interference of the K metal counter electrode is eliminated. Unlike structure modification strategies, such remarkable rate performance is originated from the low-impedance inorganic-rich KF/SnF 2 hybrid interphase on graphite. Thus, the effectiveness of the electrolyte regulation strategy highlights the underestimated rate capability of graphite anode. This renewed insight dispels the concern regarding the commercial applicability of graphite anode and enriches the advantages of PIBs for high-power density.
Haoyu Deng,Xueting Yang,Hanghang Chen,Dezhan Ye,Xiancai Jiang,Yazhou Chen,Chenyi Wang
The in-situ polymerization of 1,3-dioxolane (PDOL) in battery cells has attracted extensive attention, however, the differences of Lewis acid initiators on the DOL monomer conversion (C%) and electrochemical properties has been ignored. Here, it is demonstrated that compare with Sn(OTf) 2 Lewis acid initiator, the gelation of DOL is achieved at the lower addition of In(OTf) 3 . By optimizing their content in the gelation process, their C% are comparable which are 95.7 % and 93.5 % for In(OTf) 3 and Sn(OTf) 2 , respectively. However, the higher ionic conductivity (7.1 × 10 −4 S cm −1 at room temperature), electrochemical window (~4.5 V) and Li + transference number (0.42) are obtained for DOL initiated with In(OTf) 3 , due to its lower molecular weight which is helpful to the intermolecular Li + transport along PDOL main chain; In addition, the Li/Li symmetrical cell of In(OTf) 3 can be stably cycled for >500 h at 3 mA cm −2 , with an over-potential of 178mv. The storage and cycling impedances of half cells further proves the stable interface of In(OTf) 3 initiated DOL toward to lithium metal in comparison with those of Sn(OTf) 2 . Scanning electron microscopy results show a denser and thinner interface in the DOL catalyzed by In(OTf) 3 . Finally, the assembled Li/LiFePO 4 battery delivers specific discharge capacity and capacity retention rates of 115.5mAh g −1 and 85 %, respectively after 300 cycles at 1C. Through the initiator selection, the DOL synthesis and electrochemical properties can be tuned, which further broadens the design idea of PDOL based solid polymer electrolyte.
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