Environmentally friendly lead-free ceramics capacitors, with outstanding power density, rapid charging/discharging rate, and superior stability, have been receiving increasing attention of late for their ability to meet the critical requirements of pulsed power devices in low-consumption systems. However, the relatively low energy storage capability must be urgently overcome. Herein, this work reports on lead-free SrTi0.875Nb0.1O3 (STN) replacement of (Bi0.47La0.03Na0.5)0.94Ba0.06TiO3 (BLNBT) ferroelectric ceramics with excellent energy storage performance. Improving relaxor behaviour and breakdown strength (Eb), decreasing grain size, and mitigating large polarization difference are conductive to the enhancement of comprehensive energy storage performances. The phase-field simulation methods are further analysized evolution process of electrical tree in the experimental breakdown. In particular, the 0.70BLNBT-0.30STN ceramic exhibit a large discharged energy density of 4.2 J/cm3 with an efficiency of 89.3% at room temperature under electric field of 380 kV/cm. Additionally, for practical applications, the BLNBT-based ceramics achieve a high power density (∼62.3 MW/cm3) and fast discharged time (∼148.8 ns) over broad temperature range (20–200 °C). Therefore, this work can provide a simple and effective guideline paradigm for acquiring high-performance dielectric materials in low-consumption systems operating in a wide range of temperatures and long-term operations.