Global Portable Battery Pack Market By Type (Li-ion (Lithium ion) Battery , Li-polymer (Lithium-Polymer) Battery , Nickel Metal Hydride Battery , and Ni-Cd (Nickel Cadmium) Battery), By Application (Mobile Phones , Tablets , and Others), By Region, and Key Companies - Industry Segment Outlook, Market Assessment, Competition Scenario, Trends and Forecast 2020-2029