The 1000km range likely has more to do with the efficiency of the drivetrain and the aerodynamics of the car more than the battery tech. kWh is an absolute value that is fungible and the Denza has a 122.5 kWh battery pack, which means its getting 5mi/kWh. For perspective my Rivian R1S gets ~350 miles on a 135 kWh pack which is about 2.5mi/kWh (so about half that)
The only part of the battery tech that could affect range is the weight. Sodium batteries are typically much heavier than Li-on. I believe the Denza uses LFP, which means it's likely somewhere else on the car that they're gaining improvement in the range - not from the battery tech. That being said, the battery tech definitely affects the charge/discharge rates.