General Motors said it would delay the start of production at a planned battery plant in Indiana by about a year, to 2027, the company’s latest downshift in its move to electric vehicles. The Detroit-based automaker and Korean partner Samsung SDI disclosed the new timeline for the plant in a news release Tuesday, as they formalized plans to move forward with the $3.5 billion factory in New Carlisle, Ind. GM and its Detroit rival Ford Motor have delayed or canceled several electric-vehicle models, and production targets over the past year as U.S. consumers have been slower to embrace EVs than the automakers had once expected.