Big quote: Zeng remarking on Musk's tendency to overpromise on timelines. "Maybe something needs five years," Zeng said. "But he says two years. I definitely asked him why. He told me he wanted to push people." Robin Zeng, the founder and chairman of CATL (Contemporary Amperex Technology Co.), the world's largest EV battery company based in Ningde, China, has made a blunt assessment of Tesla's ambitious 4680 battery project, declaring it "is going to fail and never be successful." Zeng's prediction, made during an interview with Reuters, underscores a deepening debate within the EV industry regarding the future of battery technology and Tesla's strategic direction.Tesla's 4680 battery cells, named for their dimensions (46mm diameter and 80mm length), are a significant technological bet for the company. Introduced in 2020, these cells were touted as a game-changer in EV battery technology. Tesla claimed the new design would offer five times more energy capacity and significant cost reductions compared to their previous battery designs.The 4680 cells have already found their way into some Tesla vehicles, including the Cybertruck. Moreover, the company reached a significant milestone in September, announcing that it produced 100 million of these cells an achievement that came just over three months after Tesla had announced producing 50 million 4680 cells, indicating a rapid acceleration in production.Zeng and Musk reportedly clashed over Tesla's battery strategy during a heated debate in an April meeting. According to Zeng, Musk was silent in the face of Zeng's critique. "He doesn't know how to make a battery," Zeng told Reuters.Zeng believes Tesla lacks the expertise to successfully develop and manufacture the 4680 cells at scale. Indeed, scaling up production of the 4680 cells has proven difficult. Tesla has faced issues with the cells collapsing in on themselves during use. Other battery manufacturers like Panasonic have also cautioned about technical problems hindering mass production. // Related StoriesAlso, Tesla's plan to employ dry electrode technology an innovation aimed at reducing costs and improving efficiency has not achieved the anticipated results at a mass production level. This technology was a cornerstone of Tesla's vision for the 4680 cells but has posed significant implementation challenges.Tesla and CATL maintain a complex and interdependent relationship. CATL supplies batteries for Tesla's vehicles produced in China, including models sold in North America. The Chinese company specializes in lithium iron phosphate (LFP) batteries, which, while generally offering less range than cylindrical cell units, provide advantages in cost and safety.The disagreement between these two major players in the EV industry underscores the ongoing debate about the future of battery technology. While Tesla continues to heavily invest in its proprietary 4680 cells, CATL and other manufacturers are exploring alternative approaches, such as advancements in LFP batteries and the development of solid-state batteries.Zeng also touched on Musk's leadership style in the Reuters interview, particularly his tendency to set ambitious timelines. Zeng noted that Musk often promises delivery times that are shorter than realistically achievable, a strategy Musk reportedly employs to "push people." This approach has led to skepticism in the industry and among consumers, especially regarding promises about technologies like full self-driving.