June 20 (Reuters) - CYVN Holdings, a firm backed by the Abu Dhabi government, will invest about $738.5 million in Nio Inc , the Chinese electric vehicle maker said on Tuesday, as it looks to bolster the company's balance sheet. Nio and peers Xpeng and Li Auto are among those competing to grab a larger EV market share in the world's largest automotive market dominated by BYD (002594.SZ). Under the deal, Nio will issue about 85 million new Class A shares at $8.72 per share to CYVN Holdings. The news sent Nio's U.S.-listed shares down about 1% at $9.30. CYVN...