The lithium plating/stripping performance of the PVC-protected lithium anode was investigated by galvanostatic cycling tests using a symmetric Li|Li battery. As shown in
Fig. 6a, the symmetrical cells with Li-PVC anodes demonstrated excellent interfacial properties at current densities of 1 mA/cm
2 and lithium deposition capacity of 1 mAh/cm
2. Furthermore, the voltage profile of the Li-PVC anode was very stable even in cycling over 1000 h at a current density of 1 mAh/cm
2, and the high voltage hysteresis endowed the Li deposition with stronger controllability. However, the cells assembled with bare Li anode exhibited less voltage hysteresis. With the increase of cycle time, the voltage hysteresis greatly increased and the voltage plateau fluctuated significantly, which indicated that the unstable SEI was continuously broken/regenerated during the deposition/stripping process, and a large number of side reactants made the Li
+ transport difficult. Local short circuits due to uncontrolled deposition were observed at higher current densities of 3 mA/cm
2 (Fig. S9 in Supporting information). The staircase current density test also verified this, and compared to the bare Li electrode which is prone to short-circuiting, the Li-PVC electrode exhibits extremely high stability during the process of current density changes (Fig. S10 in Supporting information). Remarkably, the Li-PVC anode achieved stable Li plating/stripping for 500 h at an extremely high current density of 10 mA/cm
2 in symmetrical cells, while the bare Li anode exhibited a significant accumulation of side reactions resulting in a sharp increase in voltage hysteresis after approximately 200 h (
Fig. 6b). This demonstrates the strong application potential of the layer under high current density conditions. To evaluate the application prospects of the PVC protective layer in practical batteries, Li-PVC anodes were assembled with LFP to form Li metal full batteries. Li-PVC exhibited better cyclability. Specifically, the Li-PVC||LFP coin cell exhibited an average coulombic efficiency of 99.9% over 290 cycles at 0.5 C and exhibited a capacity retention rate of 96% (
Fig. 6c). By comparison, the bare Li||LFP coin cell showed a low-capacity retention of 79% after 290 cycles, which was attributed to the increase in cell impedance caused by the massive accumulation of side reaction products. Moreover, the Li-PVC||LFP coin cell exhibits equally excellent performance at a 5 C rate, with virtually no capacity degradation within the first 100 cycles (Fig. S11 in Supporting information). In addition, NCM811 batteries exhibited the same properties (Fig. S12 in Supporting information). Specifically, the Li-PVC||NCM811 coin cell exhibited a capacity retention of 74% after 170 cycles at 1 C. By comparison, the bare Li||NCM811 coin cell exhibited a low-capacity retention of 56% after 170 cycles. Compared to the Bare Li electrode, the Li-PVC electrode exhibits higher discharge specific capacity recovery during the transition from high to low rates, indicating that the Li-PVC has superior rate performance (Fig. S13 in Supporting information). The comparison of this work with other reports in
Fig. 6d [
45-
50], where all works used ether electrolytes with added lithium nitrate and a fixed areal capacity of 1 mAh/cm
2. It can be observed that Li-PVC exhibits excellent performance at high current density, surpassing most of the studies. This indicates that the Li-PVC strategy is promising for high current density applications.