For luxury electric cars, longer range often comes with a familiar compromise: a bigger battery adds weight. Solid-state technology could help ease that trade-off by storing more energy without requiring a heavier pack.BYD’s upcoming Yangwang executive sedan brings that possibility into the ultra-luxury conversation. Spotted testing in China, the roughly 5.5-meter (about 18 feet) vehicle combines coach doors and imposing proportions with reports that it could carry solid-state batteries.BYD has not confirmed that specification. While its appearance draws comparisons with the Rolls-Royce Phantom, the battery question connects it to a broader development effort. BMW and Mercedes-Benz are already using electric sedans to investigate how advanced cells perform beyond the laboratory.What changes inside the battery?The difference begins with the electrolyte, which allows lithium ions to move between electrodes during charging and discharging. Conventional lithium-ion cells typically use a liquid electrolyte. All-solid-state designs replace that liquid with a solid material.This change can support electrode materials such as lithium metal, potentially increasing the energy stored for a given battery weight. For an electric car, that could mean longer range without simply adding more battery mass.Mercedes-Benz identifies higher energy density as a key benefit of its solid-state development work. Safety is another potential advantage. According to the US Department of Energy, solid electrolytes are less prone to leakage when damaged, although a complete battery’s performance still depends on its materials and construction. None of these possibilities establishes the Yangwang sedan’s range or charging speed. Those figures require confirmed specifications and testing.How Yangwang supports BYD’s luxury pushYangwang occupies the highest tier of BYD’s lineup, above Denza, and showcases technologies such as the company’s quad-motor e4 platform.The upcoming sedan extends that role into the executive segment. Its long wheelbase, boxy profile and coach doors introduce styling associated with established luxury flagships, giving BYD’s technological ambitions a more traditional exterior.Yangwang general manager Hu Xiaoqing described it as “the culmination of three years of meticulous development by Yangwang, featuring the brand’s signature design language, and is an ultra-luxury executive sedan.”The combination suggests a strategy built around luxury design and technological differentiation. A solid-state battery could strengthen that positioning, but its inclusion remains unconfirmed.What road tests actually demonstrateBMW announced in May 2025 that an i7 prototype near Munich was testing Solid Power’s all-solid-state cells. Engineers are examining cell expansion, pressure control and temperature management, with BMW acknowledging that further development is needed for a competitive complete battery system. Mercedes-Benz demonstrated another step in August 2025. An EQS prototype fitted with Factorial lithium-metal solid-state cells traveled 1,205 kilometers (748.8 miles) without recharging.Mercedes reported 25 percent more usable battery energy with comparable pack size and weight. These were development results, rather than specifications for a car available to buyers.Such tests show progress while revealing the engineering work still involved. For BYD, the next step is confirmation of what powers its flagship, followed by evidence that the battery can deliver alongside the luxury experience.