Additives for electrolyte and cathode material in Li-ion batteries comprising metal-based cathode material which produces M2+ metal ions

A polymer compound having a general formula VI outlined below

• wherein:
• Q and Q′ are each independently a 5 to 12-member ring or bicycle ring, optionally either ring comprises one or more heteroatom which are the same or different;
• L is a linker comprising alkyl groups;
• Ri and R′i are each independently selected from H, alkyl, cycloalkyl, alkene, alkyne, aryl and alkylaryl, alkoxy, thioalkoxy, OH, SH, NH2, a halogen atom, a halogeno alkyl, a halogeno alkoxy, a halogeno thioalkoxy, a cyano alkyl, a cyano alkene, a cyano alkyne, CN, NO2, SO2, COOH and acyloxycarbonyl, with the proviso that at least one of Ri comprises a heteroatom and at least one of R′i is different from H;
• n and m are each independently an integer from 0 to 11 with the proviso that they are not both 0 at the same time;
• and
• the one or more heteroatom of Q or Q′ is selected from O, S and N.