Delayed Thermal Runaway Investigation on Commercial 2.6 Ah NCM-LCO Based 18650 Lithium Ion Cells with Accelerating Rate Calorimetry

The thermal runaway behavior during a nail penetration test of lithium metal oxide based commercially available 18650-type lithium ion cells was investigated regarding the influence of nail design, state of charge (SOC) and state of health (SOH) under quasi-adiabatic conditions. Whether an immediate or a delayed thermal runaway occurs, is highly dependent on the angle of the nail tip. A rather blunt nail provokes a more severe reaction leading to an immediate thermal runaway at 100% SOC. The lower the SOC, the less severe is the cell self-heating. After nail penetration further self-heating causing a thermal runaway is highly dependent on the adjusted SOC. The impacts of aging result to be beneficial for safety down to a SOH of 90%.</jats:p

Thermal analysis of LiNi0.4Co0.2Mn0.4O2/mesocarbon microbeads cells and electrodes: State-of-charge and state-of-health influences on reaction kinetics

The thermal stability of lithium ion batteries was studied by means of Accelerating Rate Calorimetry in Heat-Wait-Search operation on both electrode and cell level. Fresh and aged samples were investigated depending on the state-of-charge (SoC) of a 5 Ah pouch cell comprising mesocarbon microbeads and LiNi0.4Co0.2Mn0.4O2 as the anode and cathode materials. 1 M LiPF6 in EC:DEC 3:7 (by weight) containing 2 wt% VC and 0.5 wt% LiBOB was chosen as the electrolyte. Measurements on the electrode level revealed a higher self-heating rate (SHR) of the cathode compared to the anode for all SoC and state-of-health (SoH) combinations in the temperature range where a self-sustaining decomposition reaction could be detected. A lower SoC showed a lower SHR of the electrode/electrolyte mixture with no reaction detected on the anode side ≤ 50% cell SoC. Cyclic aging led to a decrease in thermal stability of the cathode at lower SoC values with no significant influence on the anode implying a larger safety threat on the cell level. Avrami-Erofeev and autocatalytic reaction models were used to quantify the influences of SoC and SoH on reaction kinetics. Full cell measurements confirmed the observations at a higher SHR

Soft-templating synthesis of mesoporous magnetic CuFe2O4 thin films with ordered 3D honeycomb structure and partially inverted nanocrystalline spinel domains

Combining sol-gel chemistry with polymer templating strategies enables production of CuFe(2)O(4) thin films with both an ordered cubic network of 17 nm diameter pores and tunable spinel domain sizes. These nanocrystalline materials contain only minor structural defects with λ = 0.85 ± 0.02 and exhibit multiple functionalities, including superparamagnetic behavior (T(B)≈ 310 K) and redox- and photoactivity