S T R U C T U R E O F M A T E R I A L S

S C I E N T I F I C H I G H L I G H T S

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PRINCIPAL PUBLICATION AND AUTHORS

Prevention of lithium-ion battery thermal runaway using polymer-substrate current collectors, M.T.M. Pham (a), J.J. Darst (b), W.Q. Walker (b), T.M.M. Heenan (a,c), D. Patel (a), F. Iacoviello (a), A. Rack (d), M.P. Olbinado (d), G. Hinds (e), D.J.L. Brett (a,c), E. Darcy (b), D.P. Finegan (f), P.R. Shearing (a,c), Cell Rep. Phys Sci. 2, 3, 100360 (2021); https:/doi.org/10.1016/j.xcrp.2021.100360 (a) Electrochemical Innovation Laboratory, Department of Chemical Engineering, University College London (UK) (b) NASA Johnson Space Centre, Houston, Texas (USA) (c) The Faraday Institution, Harwell Science and Innovation Campus, Oxford (UK) (d) ESRF (e) National Physical Laboratory, Teddington, London (UK) (f) National Renewable Energy Laboratory, Golden, Colorado (USA)

REFERENCES

[1] D.P. Finegan et al., Nat Commun. 6 (2015). [2] D.P Finegan et al., Energy Environ. Sci. 10, 1377 (2017).

Operando non-stoichiometry measurement during chemical- looping H2 production

H2 is an important feedstock for many industrial processes and could be an energy carrier in a low- carbon economy. This work compares simulations to operando oxygen content measurement of a chemical-looping H2 production reactor with inherent carbon separation, and finds excellent agreement.

Approximately 60 million tonnes of H2 is produced annually, the majority of which is derived from fossil fuels. The production of H2 from fossil fuels or biomass conventionally uses water gas shift (WGS) reactors. This is a mature, efficient and well-developed technology

that can achieve high conversion to H2 but requires low temperatures (~473 K) for thermodynamic reasons, resulting in less favourable kinetics. This leads to large catalytic reactors, highly optimised and expensive catalysts, and requires the gas streams to be cooled from around 1073 K before entering the reactor. Additionally, if pure H2 is required, then further separation processes such as pressure swing adsorption are needed.

In comparison, chemical-looping H2 production allows inherent separation of the product gases by splitting the reaction into two or more sub-reactions through the use of a solid oxygen carrier (OC). The WGS reaction (eq.1) can, in this way, be implemented in a chemical-looping reactor. The OC (here La0.6Sr0.4FeO3-δ) first reacts with CO (eq.2) and is subsequently re-oxidised by H2O to produce H2 (eq.3). The carbon-containing gases are never

As the nail penetrates the electrode layers, an initial microscopic short-circuit occurs with the nail acting as the connective bridge between the positive and negative electrode. This causes a very high current delivery due to the short-circuit to the region, and elevated local temperatures can be attributed to Ohmic heating. The commercial pure metal current collectors have no mitigating properties, and this region continues to heat, developing into a macroscopic short-circuit and resulting in widespread thermal runaway, as shown in Figure 132a and Figure 133a.

However, with the PCC, the increasing temperature due to the microscopic internal short-circuit causes the PCC to shrink back from the region of nail penetration. This thermally induced change in the PCC prevents further contact with the nail and thus, current delivery to the short-circuit is stopped, as shown in Figure 132b and Figure 133b. This function of the PCC operates before

other thermally susceptible cell components or cell safety features are compromised.

The results presented here demonstrate a great advancement in improving the safety of lithium-ion batteries, with Al-PCC cells consistently exhibiting thermal runaway prevention before thermal degradation of other components and compromise of other cell safety features. The innovative structure provided by the PCC architecture offers the safety advances reported here, which are independent of cell chemistry (provided the PCC is stable in the operating environment). Beyond the safety improvements demonstrated in this work, the PCCs also use less metal than conventional current collectors, thus reducing cost and material use within cells. The combined safety and cost advantages are expected to accelerate adoption of Li-ion batteries when PCCs become widespread in commercial cells.