Fig. S1 b) Plot of specific capacity and Coulombic efficiency vs. cycle number of SnSe in Na half-cell (Al current collector) at 150 mA g−1.			
cycle number	discharge capacity/mAhg-1	charge capacity/mAhg-1	efficiency/%
1	107.556	345.11	31.16572
2	100.662	122.821	81.9583
3	96.9589	112.372	86.28386
4	94.3812	106.356	88.74083
5	92.5441	102.567	90.22795
6	91.0713	99.8431	91.21442
7	89.8473	97.745	91.9201
8	88.8174	96.1037	92.41829
9	87.9147	94.7304	92.80516
10	87.1339	93.5988	93.09297
11	86.4325	92.6155	93.32401
12	85.8044	91.7679	93.50154
13	85.2318	91.0346	93.62572
14	84.6824	90.3378	93.73972
15	84.187	89.7061	93.84758
16	83.7193	89.1374	93.92163
17	83.2871	88.5932	94.01071
18	82.8453	88.0629	94.07514
19	82.3974	87.5302	94.13597
20	81.9978	87.0251	94.22316
21	81.5757	86.5535	94.24887
22	81.2033	86.0895	94.32428
23	80.8207	85.6688	94.34088
24	80.4523	85.2349	94.38892
25	80.0887	84.8326	94.40793
26	79.7386	84.4529	94.41784
27	79.3762	84.0622	94.42556
28	79.0739	83.7679	94.39642
29	78.6968	83.3402	94.42838
30	78.3389	82.9855	94.40071
31	78.0307	82.6727	94.38509
32	77.6962	82.3202	94.38291
33	77.3562	81.9766	94.36376
34	77	81.6238	94.33523
35	76.6627	81.2788	94.32066
36	76.346	80.9163	94.35182
37	75.982	80.5875	94.28509
38	75.6414	80.1953	94.32149
39	75.3125	79.8804	94.28158
40	74.9602	79.5249	94.26004
41	74.6151	79.1621	94.25609
42	74.2513	78.7864	94.2438
43	73.9104	78.4514	94.2117
44	73.5506	78.0679	94.21363
45	73.1641	77.6809	94.18544
46	72.7992	77.3012	94.17603
47	72.4119	76.9381	94.11709
48	72.1483	76.5799	94.2131
49	71.7425	76.2086	94.13964
50	71.3972	75.8543	94.12413
