Database: scholar
Question: What did Liwen Xiong published in 2015 ?
SQL:
SELECT DISTINCT t3.paperid FROM writes AS t2 JOIN author AS t1 ON t2.authorid  =  t1.authorid JOIN paper AS t3 ON t2.paperid  =  t3.paperid WHERE t1.authorname  =  "Liwen Xiong" AND t3.year  =  2015;