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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Overcharge-to-thermal-runaway behavior and safety assessment of commercial lithium-ion cells with different cathode materials: A comparison study

In this paper, overcharge behaviors and thermal runaway (TR) features of large format lithium-ion (Li-ion) cells with different cathode materials (LiFePO 4 (LFP), Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 (NCM111), Li[Ni 0.6 Co 0.2 Mn 0.2 ]O 2 (NCM622) and Li[Ni 0.8 Co 0.1 Mn 0.1 ]O 2 (NCM811)) were investigated. The results showed that, under the same overcharge condition, the TR of LFP Li-ion cell occurred earlier compared with the NCM Li-ion cells, indicating its poor overcharge tolerance and high TR risk. However, when TR occurred, LFP Li-ion cell exhibited lower maximum temperature and mild TR response. All NCM Li-ion cells caught fire or exploded during TR, while the LFP Li-ion cell only released a large amount of smoke without fire. According to the overcharge behaviors and TR features, a safety assessment score system was proposed to evaluate the safety of the cells. In short, NCM Li-ion cells have better performance in energy density and overcharge tolerance (or low TR risk), while LFP Li-ion cell showed less severe response to overcharging (or less TR hazards). For NCM Li-ion cells, as the ratio of nickel in cathode material increases, the thermal stability of the cathode materials becomes poorer, and the TR hazards increase. Such a comparison study on large format Li-ion cells with different cathode materials can provide deeper insights into the overcharge behaviors and TR features, and provide guidance for engineers to reasonably choose battery materials in automotive applications.

25 ENERGY STORAGE↗
NASA NTRS1991

Analysis of redox additive-based overcharge protection for rechargeable lithium batteries

The overcharge condition in secondary lithium batteries employing redox additives for overcharge protection, has been theoretically analyzed in terms of a finite linear diffusion model. The analysis leads to expressions relating the steady-state overcharge current density and cell voltage to the concentration, diffusion coefficient, standard reduction potential of the redox couple, and interelectrode distance. The model permits the estimation of the maximum permissible overcharge rate for any chosen set of system conditions. Digital simulation of the overcharge experiment leads to numerical representation of the potential transients, and estimate of the influence of diffusion coefficient and interelectrode distance on the transient attainment of the steady state during overcharge. The model has been experimentally verified using 1,1-prime-dimethyl ferrocene as a redox additive. The analysis of the experimental results in terms of the theory allows the calculation of the diffusion coefficient and the formal potential of the redox couple. The model and the theoretical results may be exploited in the design and optimization of overcharge protection by the redox additive approach.

Narayanan, S. R.↗
NASA NTRS1991

Finite linear diffusion model for design of overcharge protection for rechargeable lithium batteries

The overcharge condition in secondary lithium batteries employing redox additives for overcharge protection has been theoretically analyzed in terms of a finite linear diffusion model. The analysis leads to expressions relating the steady-state overcharge current density and cell voltage to the concentration, diffusion coefficient, standard reduction potential of the redox couple, and interelectrode distance. The model permits the estimation of the maximum permissible overcharge rate for any chosen set of system conditions. The model has been experimentally verified using 1,1-prime-dimethylferrocene as a redox additive. The theoretical results may be exploited in the design and optimization of overcharge protection by the redox additive approach.

Narayanan, S. R.↗
NASA NTRS1992

Protecting Li/TiS2 Cells Against Overcharge

New electrolyte additive, N,N,N',N'- tetramethyl-1,4-phenylenediamine (TMPD), helps protect lithium/titanium disulfide rechargeable cells against overcharge. TMPD is redox couple: during overcharge, it undergoes electrochemical reactions at both electrodes and takes up excess input charge. Without TMPD, overcharge results in oxidative degradation of nonaqueous electrolyte, leading to loss of rechargeability and safety problems. Li/TiS2 cells currently being considered for spacecraft and military applications.

Narayanan, S. R.↗
DOE OSTI2022

Investigation and Suppression of Oxygen Release by LiNi 0.8 Co 0.1 Mn 0.1 O 2 Cathode under Overcharge Conditions

The safety issue of lithium-ion batteries is a crucial factor limiting their large-scale application. Therefore, it is of practical significance to evaluate the impact of their overcharge behavior because of the severe levels of oxygen release of cathode materials during this process. Here, by combining a variety of in situ techniques of spectroscopy and electron microscopy, this work studies the structural degradation of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) accompanying the oxygen release in the overcharge process. It is observed that a small amount of O 2 evolves from the initial surface at ≈4.7V. When charging to a higher voltage (≈5.5V), a large amount of O 2 evolves on the newly formed surface due to the occurrence of microcracks. Based on experimental results and theoretical calculations, it is determined that the oxygen release mainly occurs in the near-surface regions, where the remaining oxygen vacancies accumulate to create voids. To suppress the oxygen release, single-crystalline NCM811 with integrated structure is introduced and serves as a cathode, which can effectively inhibit morphology destruction and reduce the activation of lattice oxygen in the surface region. These findings provide a theoretical basis and effective strategy for improving the safety performance of Ni-rich cathode materials in practical applications.

25 ENERGY STORAGE↗
DOE OSTI2022

Trivalent ion overcharging on electrified graphene

We report the structure of the electrical double layer (EDL) formed near graphene in aqueous environments strongly impacts its performance for a plethora of applications, including capacitive deionization. In particular, adsorption and organization of multivalent counterions near the graphene interface can promote nonclassical behaviors of EDL including overcharging followed by co-ion adsorption. In this paper, we characterize the EDL formed near an electrified graphene interface in dilute aqueous YCl 3 solution using in situ high resolution x-ray reflectivity (also known as crystal truncation rod) and resonant anomalous x-ray reflectivity (RAXR). These interface-specific techniques reveal the electron density profiles with molecular-scale resolution. We find that yttrium ions (Y 3+ ) readily adsorb to the negatively charged graphene surface to form an extended ion profile. This ion distribution resembles a classical diffuse layer but with a significantly high ion coverage, i.e., 1 Y 3+ per 11.4 ± 1.6 Å 2 , compared to the value calculated from the capacitance measured by cyclic voltammetry (1 Y 3+ per ~240 Å 2 ). Such overcharging can be explained by co-adsorption of chloride that effectively screens the excess positive charge. The adsorbed Y 3+ profile also shows a molecular-scale gap (≥ 5 Å) from the top graphene surfaces, which is attributed to the presence of intervening water molecules between the adsorbents and adsorbates as well as the lack of inner-sphere surface complexation on chemically inert graphene. We also demonstrate controlled adsorption by varying the applied potential and reveal consistent Y 3+ ion position with respect to the surface and increasing cation coverage with increasing the magnitude of the negative potential. This is the first experimental description of a model graphene-aqueous system with controlled potential and provides important insights into the application of graphene-based systems for enhanced and selective ion separations.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS1977

Determination of overcharge protection

Nylon separator degradation was examined as a function of temperature. Electrochemically active uncharged excess negative (overcharge protection)was measured by charging a cell venting it until it became fully charged, and continuing to overcharge the vent gas. The gas was analyzed as a function of time. The amount of hydrogen evolved was examined, and the cell voltage was observed as the oxygen and/or hydrogen evolved from the cell.

Scott, W. R.↗
NASA NTRS1992

Heat generation during overcharge of Ni/H2 cells

Information is given in viewgraph form on the heat generation during overcharge of nickel hydrogen cells. The heat dissipated during various rates of charge and overcharge was measured, using a radiative type calorimeter. Measurements made during the charging of the cell indicated that the total heat was greatest for C/10 charge, compared with C/2 or C/4. The endothermic to exothermic transition occurred at 1.43 V for C/10 charge, and increased to 1.467 V at C/2 charge. The magnitude of the endothermic heat was only 3.7 percent of the total heat generated during charging. Experimentally measured values were compared against those calculated using a thermoneutral potential of 1.51 V. Although there was general agreement between the calculated and measured values, a significant difference existed in the instantaneous heat values for the initial stages of cell discharge. Heat dissipated during self-discharge appears to depend on the charge rate preceding open circuit stand.

Vaidyanathan, Hari↗
NASA NTRS1995

Preventing Overcharge And Overdischarge Of Lithium Cells

Secondary lithium cells operating at ambient temperature protected against overcharge and overdischarge by use of cathode additives acting as sources and sinks of electroactive chemical species, which is lithium. Additive in cathode limits excursion of voltage of cell during both overcharge and overdischarge. In addition to protecting cell, also serves as part of state-of-charge indicator: attainment of greater or lesser limiting voltage indicates end of charge or end of discharge, respectively. Concept applied to Li/TiS2 system, and also applicable to such other lithium systems as Li/MoS2, Li/NbSe3, and Li/V2O5.

Huang, Chen-Kuo↗
DOE OSTI2022

Nanotomographic observation and statistical analysis of overcharging induced cracks in LiCoO 2 single crystalline particles

Particle fracture represents an important mode of battery electrode degradation. Extensive cracking occurs in the layered oxide cathodes of lithium-ion rechargeable batteries when they are charged beyond safe operational voltages. In this paper, we analyze the morphology and distribution of cracks in over 100 overcharged LiCoO 2 (LCO) single-crystalline particles imaged via X-ray nanotomography. Herein, we observe a strong particle size dependence in both nucleation and growth of cracks, with percentage of cracked particles, crack size, and crack surface area per unit volume all increasing significantly with particle volume. Increasing the cutoff voltage above 4.6V is found to trigger much more pronounced crack growth, which we attribute to the large misfit stress caused by the H1-3 to O1 phase transition. This study offers valuable statistical insights into the fracture behavior of layered oxide cathodes and reveals the importance of particle size control on electromechanical degradation of battery electrodes.

25 ENERGY STORAGE↗
DOE OSTI2020

Effect of overcharge on Li(Ni 0.5 Mn 0.3 Co 0.2 )O 2 /Graphite cells–effect of binder

Cells based on NMC/graphite, containing styrene-butadiene rubber/carboxymethylcellulose binder in the anodes and pVdF latex/carboxymethykellulose in the cathodes, were systematically overcharged to 100, 120, 140, 160, 180, 250% and 270% state-of-charge. The impact of the binder was characterized by elemental analysis, SEM, and HPLC. These results were compared to similar cells just using the poly (vinylidene difluoride) binder. Not only did the binder impact the rate of transition metal transport from the cathode to the anode, it also had a marked effect on the microstructure and composition of the materials on the anode surface.

25 ENERGY STORAGE↗
DOE OSTI2022

Direct Imaging of the Structural and Morphological Evolution of Epitaxial LiCoO 2 Films during Charge and Overcharge

The capacity decay of layered cathodes in high-voltage applications underscores the need to utilize accurate and precise techniques to understand the underlying mechanisms. Here, we use well-defined epitaxial LiCoO 2 (LCO) films on SrRuO 3 /SrTiO 3 (SRO/STO) with controlled orientations and defect structures along with in situ electrochemical atomic force microscopy to probe the structural and morphological evolutions during the charge and overcharge processes. We quantitatively show the morphological changes in both the reversible delithiation regime and the irreversible over-delithiation regime and correlate the overall electrochemical behaviors to atomic scale defect evolutions in the films. Further, we also observe a significantly lower charging capacity for LCO/SRO/STO(111) compared to that of LCO/SRO/STO(001) films of the same thickness, which is ascribed to different types of atomic scale defects formed during the film growth process. Our high- resolution scanning transmission electron microscopy (STEM) and electron energy loss spectroscopy (EELS) studies reveal that the antiphase boundaries in LCO/SRO/STO(111) act as viable channels for Li migration but are more susceptible to irreversible phase transitions, which then block subsequent Li diffusion. The failure mechanisms developed here may provide insight into the design of future cathode materials.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Direct Experimental Observations of Ion Distributions during Overcharging at the Muscovite–Water Interface by Adsorption of Rb + and Halides (Cl – , Br – , I – ) at High Salinity

Classical electric double layer (EDL) models have been widely used to describe ion distributions at charged solid-water interfaces in dilute electrolytes. However, the chemistry of EDLs remains poorly constrained at high ionic strength where ion-ion correlations control non-classical behavior such as overcharging, i. e., the accumulation of counter-ions in amounts exceeding the substrate's surface charge. Here, we provide direct experimental observations of correlated cation and anion distributions adsorbed at the muscovite (001)-aqueous electrolyte interface as a function of dissolved RbBr concentration ([RbBr]=0.01–5.8 M) using resonant anomalous X-ray reflectivity. Our results show alternating cation-anion layers in the EDL when [RbBr]≳100 mM, whose spatial extension (i. e., ~20 Å from the surface) far exceeds the dimension of the classical Stern layer. Comparison to RbCl and RbI electrolytes indicates that these behaviors are sensitive to the choice of co-ion. This new in-depth molecular-scale understanding of the EDL structure during transition from classical to non-classical regimes supports the development of realistic EDL models for technologies operating at high salinity such as water purification applications or modern electrochemical storage.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1966

Circuit prevents overcharging of secondary cell batteries

Circuit prevents battery cell overcharging by detecting and reducing the charging voltage to the open-circuit voltage of the battery when this current falls to a predetermined value. The voltage control depends on the fact that the charging current falls significantly when the battery nears its fully charged state.

Hennigan, T. J.↗