The efficiency and toxicity of dodecafluoro-2-methylpentan-3-one in suppressing lithium-ion battery fire

Currently,the effective and clean suppression of lithium-ion battery(LIB)fires remains a challenge.The present work investigates the use of various inhibitor doses(Xin)of dodecafluoro-2-methylpentan-3-one(C_(6) F_(12)O)in 300 Ah LIBs,and systematically examines the thermal and toxic hazards of the extinguished batteries via real scale combustion and gas analysis.The inhibitor is shown to be completely effective.The inhibition mechanism involves a combination of chemical inhibition and physical cooling.While the chemical inhibition effect tends to saturate with increasing Xin,the physical cooling remains effective at higher inhibitor doses.However,extinguishing the battery fire with a high Xin of C_(6)F_(12)O is found to incur serious toxicity problems.These results are expected to provide a guideline for the design of inhibitor doses for the suppression of LIB fires.

Insight into the structural evolution and thermal behavior of LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2) cathode under deep charge

By virtue of the crucial effect of the crystal structure and transition metal(TM)redox evolution on the performance of LiNi_(x)Co_(y)Mn_(z)O_(2)(NCM)cathode,systematical investigation is carried out to better understand the charge mechanism upon deep charging.Based on the results of X-ray diffraction and highresolution transmission electron microscope,phase transformations existing on particle surface are promoted by high potential because of the deeper lithium vacancies,accompanied by more substantial structure instability.Soft X-ray absorption spectroscopy indicates that Ni acts as the major contributor to charge compensation while Co displays a remarkable redox activity over the deep charge range.The elevated integrated intensity of pre-edge in O K-edge spectra reveals the extensive amount of holes formed in O 2 p orbitals and the enhanced hybridization of TM 3 d-O 2 p orbitals.Considering the close relationship between thermal behavior and structural evolution,the tendency of phase transitions and O_(2) release upon heating is accelerated by voltage rise,demonstrating the aggravated instability due to deeper Li utilization.Remaining Li contents in NCM are employed to estimate the amount of oxygen released in structural transformation and its detrimental effect on stability declares Li contentdependent characteristics.Furthermore,the extended Li vacancies,higher proportion of Ni4+and stronger orbital hybridization are considered as three factors impeding the thermal stability of the highlydelithiated NCM.

Transition-metal redox evolution and its effect on thermal stability of LiNixCoyMnzO_(2) based on synchrotron soft X-ray absorption spectroscopy

Based on the synchrotron soft X-ray absorption spectroscopy experiments,the fundamental electronic structures of layered Li NixCoyMnzO_(2)(NCM)are investigated systematically and the data of transitionmetal(TM)L-and O K-edges spectra are collected.Distribution of Ni ions under different oxidation states is evaluated according to linear combination fit.It is found that the ratio of Ni^(4+)expands with the increase of Ni since it dominates in charge compensation during charging,and that the existence of Ni^(3+)is nearly negligible in delithiated NCM.The valence state of Co also strongly depends on Ni content,the perceptible position shift of Co L_(3)-edge absorption peak towards higher energy in Ni-rich material agrees well with the small voltage plateau at around 4.2 V.The stability of Mn is verified as no obvious spectral change with the Mn L-edge is observed.Moreover,as Ni content rises,the O 2p holes near the Femi level increases with higher oxidation state of Ni,indicating the enhanced hybridization of O 2p-TM 3 d.Delithiated NCMs with higher Ni content are prior to lose electron existing in highly hybridized Ni3 dO 2 p bands upon heating,which accounts for the pronounced O_(2)release in phase transitions and the deterioration in thermal stability.These detailed observation of the electronic structure evolution is one of the key ingredients to improving the electrochemical and thermal performance of NCM.

Precise in-situ and ex-situ study on thermal behavior of LiNi_(1/3)Co_(1/3)Mn_(1/3)O_(2)/graphite coin cell:From part to the whole cell

Multiple mode calorimetry and C80 micro-calorimeter are used to investigate the impact of cathode and anode on heat generation of lithium ion battery.The thermal behaviors of LiNi_(x)Co_(y)Mn_(z)O_(2)/graphite full cell are discussed under normal operating and elevating temperature.Affected by negative entropy change,lithium intercalation presents more exotherms than deintercalation for both electrode materials.The contributions of irreversible and reversible heat to the total heat generation of graphite are evaluated.The phase transitions correlated with voltages and lithium contents are determined.Based on the analysis of half-cell,the effect of two electrodes(with the same capacity)on overall heat generation is nearly the same and anode of full cell plays a key role in charging while cathode dominates in discharging.Thermal behaviors of lithiated graphite and delithiated LiNi_(x)Co_(y)Mn_(z)O_(2) electrolyte and their coexisting system are identified to further explore their influence on battery safety.The breakdown of solid electrolyte interface(SEI)at around 82℃ is considered as a crucial factor affecting the thermal stability of full cell.The oxidation of electrolyte induced by oxygen released from cathode material turns out to be one of the main heat sources.These accurate results are of great significance to improve the existing thermal management system and provide basic data for the prediction of battery performance.