Making Batteries Last Longer A low-cost practical diagnosis technique for lithium-ion batteriesYu Merla1, Yatish Patel1, Billy Wu1, Vladimir Yufit1

, Joel Sylvester2, Gregory Offer1

1 Department of Mechanical Engineering, Imperial College London2 Dukosi Ltd.

[1] Novel application of differential thermal voltammetry as an in-depth state of health diagnosis method for lithium-ion batteries. Y.

Merla et. al. Power Sources. 307 (2016) 308–319. doi:10.1016/j.jpowsour.2015.12.122.

[2] Differential thermal voltammetry for tracking of degradation in lithium-ion batteries, B. Wu, et. al. Power Sources. 273 (2015) 495–

501. doi:10.1016/j.jpowsour.2014.09.127.

1. Differential Thermal Voltammetry (DTV)• Novel in-situ diagnosis technique for tracking degradation in lithium-ion batteries• Only required voltage and surface temperature measurement• Carried out by observing entropic heat changes during a galvanostatic charge or discharge• Its simple computation can be handled by existing battery management systems• Low cost hardware and software requirements makes DTV a practical technique for applications such as

electric vehicles and smartphones.• dT/dV plotted against potential to give indication on changes in electrode stoichiometry• Each dT/dV peak represents a combination of different contributions from positive and negative

electrode phases

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2. Accelerated aging and DTV peak analysis experiment

3. DTV on a 4 cell battery pack

Cell Load Temperature

1 Held at 4.2V 55 ºC

2 1C cycling 55 ºC

• Commercial 5Ah lithium-ion cells• Carbon negative electrode• Nickel manganese cobalt oxide

positive electrode

DTV successful in detecting degraded cell in pack information as good as slow-rate cyclic voltammetry and

incremental capacity method Additional information on the entropy characteristics Can be carried out during a 1C – 3C charge or discharge Standard thermocouple to measure surface temperature

Evolution of decoupled DTV peaks used to track electrode stoichiometry Changes in peak parameters identify stoichiometric drift in cell 1 No significant stoichiometric drift is observed for cell 2 despite similar capacity loss Such findings can be used for adaptive control of cell operation to optimise cell

lifetime and available energy

4. Real-time application

• Working with Dukosi Ltd. to implement DTV technology onto distributed BMS board.

• Places a permanent memory on each cell to record its lifetime service history. Effectively providing a verifiable 'CV' for each cell. Thus reducing repackaging costs and enhances battery value.

• The technology architecture involves less wiring than traditional BMS systems and allowing for the simple design and reconfiguration of battery packs.

• System is cell chemistry and format agnostic, powered by the cell itself.