Aging and thermal behavior of lithium-ion battery under high charging current cycling

• Interactions among battery aging, material degradation and heat generation are found. • Thermal behavior of battery fast charge during the whole cycling life is revealed. • Robust SEI formation curbs mid-late lithium plating and reduces heat peaks. • Age and thermal behavior of battery under different fast charging methods are studied. • Fast discharging induces local lithium plating. To investigate the aging and heat-generation mechanisms of lithium-ion batteries under high-rate charging, we performed cycle-life tests using five charging protocols: 2C CC, 3C CC, 4C CC, 4C CC–CV 15 min, and 4C CC–CV 60 %SOC. The data show that increasing the C-rate accelerates early capacity loss driven by irreversible lithium loss (LLI), active material loss (LAM), and rising contact resistance; however, once a robust SEI layer forms, lithium plating is suppressed and the rates of capacity fade and impedance growth partially stabilize. Under 2C CC cycling, impedance and capacity loss worsen continuously. At 3C CC and 4C CC, impedance and capacity degrade rapidly at first but then plateau or slow in the mid-to-late stages as the SEI stabilizes. In contrast, 4C CC–CV exhibits only mild LLI and LAM initially, but both accelerate more sharply thereafter, producing the fastest capacity fade; the 4C CC–CV 15 min protocol reaches end-of-life first. Joule heating and side-reaction heat jointly dominate total heat generation, and peak cell temperature rises with C-rate. Early in 4C CC–CV 15 min cycling, the battery attains its highest temperature, while at end-of-life under 4C CC–CV 60 %SOC it remains elevated. Higher C-rates also exacerbate cathode particle degradation and promote more byproduct formation: manganese dissolves from the cathode and deposits on the anode surface, and cobalt dissolution and deposition become more pronounced at high rates and SOC.