BEIJING, Dec 1 (Reuters) - The head of China's Zijin Mining Group Co Ltd (601899.SS) said lithium prices now at record levels could halve by end-2025, telling the Reuters NEXT conference however the miner would still forge ahead with heavy investment in the sector. The company, China's top gold extractor and a leading producer of copper, has already spent $16 billion buying three lithium mines over the past year, making it one of the world's top 10 producers of the battery metal. The flurry of deals comes even as warnings emerge that lithium prices, driven to records by rapid growth...