Energy storage systems for deep decarbonization: A critical review

Energy storage technologies are fundamental to achieving global climate targets because they enable the large-scale integration of variable renewable energy into reliable power systems. This review examines the current status and future role of energy storage in deep decarbonization, focusing on technological progress, economic performance, and sustainability challenges. Lithium-ion batteries have reached commercial maturity, with average pack costs falling from $139/kWh in 2023 to approximately $70/kWh for stationary applications by 2025. Lithium iron phosphate (LFP) chemistries now dominate the market, accounting for approximately 74% of cathode material shipments in China and nearly 45% of global electric-vehicle battery capacity, driven by lower costs, improved safety, and longer lifetimes compared with nickel-based alternatives. While lithium-ion systems are well suited for short-duration storage, higher shares of renewable electricity require long-duration solutions, including sodium-ion batteries, solid-state systems, iron-air storage, and green hydrogen. Hydrogen remains one of the few options for seasonal energy storage, but it faces key limitations related to low round-trip efficiency, high infrastructure requirements, and water intensity relative to direct electrification. Scaling storage to support net-zero pathways also presents a sustainability challenge, as it demands a major expansion of critical mineral extraction with associated environmental and geopolitical risks. Although battery manufacturing emissions can be reduced by up to 70% through renewable-powered production, these gains must be supported by robust circular economy strategies. Economic analyses show storage approaching cost parity with fossil-fuel peaker plants, yet current market structures undervalue its grid services. Achieving the Paris Agreement's 45% emissions reduction by 2030—equivalent to 19–20 Gt CO 2 per year—will require coordinated policy, market reform, and rapid deployment, with storage-enabled renewables potentially delivering 2–3 Gt CO 2 per year of abatement if annual deployment exceeds 500 GWh. • Critical review of storage technologies for deep decarbonization to 2050 • LFP chemistry dominates Li-ion market with 74% share and cost < $100/kWh. • Sodium-ion and solid-state batteries analyzed as key post-2025 solutions • Green hydrogen viability analyzed against efficiency and water constraints • Policy reforms and circular economy are vital for 1.5 °C climate targets.