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=== Nickel-Hydrogen Batteries ===
These have found wide use in high-reliability space applications that require extended service life. Replacement of Cd with hydrogen reduced weight and increased energy thus almost doubling the specific energy. The cells often appear capable of handling the stresses of inadvertent reversal or excessive overcharge with little evidence of the damage or performance degradation that had been the rule for nickel-cadmium cells. <ref>http://aerospace.wpengine.netdna-cdn.com/wp-content/uploads/2012/03/bk_ni-hyd-batteries-prin-pract_ch1.pdf <\/ref>
=== Li-ion Batteries ===
High energy density, high specific energy and long cycle life make Li-ion batteries promising power sources for satellites. It offers significant advantages in terms of mass(almost half of nickel hydrogen batteries for the same stored energy), volume and temperature range. The batteries also display good tolerance to occasional deep discharge. Li-Ion cells also display impressive and adequate tolerance to radiation levels as high as 18 Mrad (1 rad=0.01 J/kg ; dose causing 100 ergs of energy to be absorbed by 1 gram of matter) and exhibit a loss of less than 10 % upon such high levels of radiation exposure. Furthermore, a portion of this loss can be attributed to the cycling or storage during this incremental radiation exposure. <ref name = "ieee"/> <br \>
Significant advances have been made in the cathode materials and electrolytes for Li-ion cells and batteries. Several new cathodes with high specific capacity approaching 250 mAh/g, coupled with high voltage and improved thermal stability have been identified. Likewise, several new electrolytes for enabling operations at -60 °C have been demonstrated. These advances are expected to results in advanced lithium-ion cells and batteries with high specific energy and wide range of operating temperatures, as desired in future space missions. <ref name = "ieee"/> However, the polymer li-ion cells have an additional problem with electrolyte leakage under abusive conditions. <ref name = "nasa">https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20090023862.pdf</ref>
=== Comparison between the batteries ====