Laser welding is the key technology of new energy battery manufacturing. To ensure the full absorption of pump light and laser light conversion efficiency, 976 nm semiconductor laser pump technology is used, and the length of gain fiber is shortened to increase the laser stimulated Raman scattering threshold. And a novel gain fiber coiling method is provided to suppress the mode instability and improve the output beam quality. The output power of single-mode (M²≤1.1) laser is 2.25 kW, the Raman suppression ratio reaches -38 dB, and the length of energy transmission fiber (14 μm core diameter, numerical aperture is 0.07) reaches 7 m. The output laser has high brightness, small spot diameter, and high power density, which can effectively reduce the thermal effect during welding and avoids weld defects and spatters.