 Shares of Expion360 Inc. XPON, 143.19 rocketed 154.5 in very active midday trading Friday, enough to make them the biggest gainers listed on major U.S. exchanges, after the maker of lithium batteries for recreational vehicles and the marine industry announced an exclusive supply agreement. Trading volume ballooned to 34.2 million shares, compared with the full-day average over the past 30 days of about 209,900 shares. 