Batteries made by Yardley Lithion
Well discussed here:
Life verification of large capacity Yardney Li-Ion cells and batteries in
support of NASA missions
One version 60% capacity after 3000 cycles deep discharge
Another - 25,000 cycles, 40% depth of discharge 35 min charge/discharge periods (LEO satellite simulation). Max Voltage = 3.8V/cell!
Next Generation and Domestically Produced Active Materials for Lithium-Ion Cells
for Military and Aerospace Applications
Adding material from comments that increases usefulness of answer
PJC in Jan 2013 noted that majopr points from the paper cited above included
- "the capacity fade at lower temperature is significantly decreased" (-20 degrees C).
and
" ... also to keep the rate and depth of discharge low ("battery could not support rate of discharge >C/2 at -20C when <75% charged after 1010 sols of operation"), and for long term storage to keep the batteries at 50-70% charge, not fully charged."
He also noted - The anode composition and surface coating may also be different from consumer batteries.