Fig. 1

(a) XRD patterns and (b) TG curve of PB material; (c) weight loss and water content tests results of PB electrode"

Fig. 2

The first three charge-discharge curves of coin-type (a) PB/Na half cell and (b) HC/Na half cell"

Fig. 3

(a) Overdischarge plot to 0 V at 0.2 C and recovery discharge plot to 1.5 V at 0.2 C of PB/HC battery; (b) battery appearance before and after overdischarge"

Table 1

Overdischarge performance of PB/HC and LFP/G batteries"

Fig. 4

(a) Overdischarge plot to -3.6 V at 0.2 C and recovery discharge plot to 1.5 V at 0.2 C of PB/HC battery; (b) appearance of separator and electrode after overdischarge"

Table 2

Gas composition in PB/HC battery after overdischarge"

Fig. 5

(a) Overdischarge plot to -1.4 V at 0.2 C of LFP/G battery; (b) appearance of separator and electrode after overdischarge"

Fig. 6

Overcharge performance of PB/HC batteries at 0.5 C: (a) 20% overcharge, (b) 30% overcharge and (c) 40% overcharge"

Table 3

Overcharge performance of PB/HC batteries"

Fig. 7

Cycling performance of PB/HC Na-ion batteries without overcharge and with 20% overcharge at 0.5 C in a voltage range of 1.5～3.6 V; (b) batteries appearance after 490 cycles"

Fig. 8

SEM Photograph of PB electrodes after (a) normal charge to 3.6 V and (b) 20% overcharge"

Fig. 9

Short circuit test of PB/HC batteries: (a) battery appearance before test and (b) battery appearance after test"

Table 4

Short circuit, nail penetration and heating tests of PB/HC batteries"

Fig. 10

Nail penetration test of PB/HC batteries: (a) battery appearance before test and (b) battery appearance after test"

Fig. 11

Heating test of PB/HC batteries: (a) battery appearance before test and (b) battery appearance after test"