The search for high cycle life, high capacity, self healing negative electrodes for lithium ion batteries and a potentia
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The search for high cycle life, high capacity, self healing negative electrodes for lithium ion batteries and a potential solution based on lithiated gallium
Mark W. Verbrugge,1 Rutooj D. Deshpande,2 Juchuan Li,2 and Yang-Tse Cheng2 1
Chemical Sciences and Materials Systems Laboratory, General Motors Research and
Development Center, Warren, MI 48090, USA 2
Department of Chemical and Materials Engineering, University of Kentucky, Lexington,
Kentucky 40506, USA
ABSTRACT Automotive components, for the most part, are designed to last for the life of the vehicle. This is especially true for more expensive subsystems. As we move towards electrified vehicles with large traction batteries, it becomes increasingly important to (a) reduce the cost of the batteries and (b) improve battery life. This life challenge for the traction battery is quite different from that of most consumer electronics applications, which often require no more than a few years of life and a few hundred cycles of full charge and discharge. In this paper, we provide context for the automotive battery landscape and subsequently introduce a potential solution pathway to the cycle life problem associated with high capacity negative electrodes for lithium ion batteries. The approach is based on a solid (in the substantially lithiated state) to liquid (in the absence of significant lithium) transition for the gallium electrode. Because of gallium’s low melting point (29°C), heating the cell to just above ambient temperature transforms the electrode to a semi-liquid state, cracks vanish, to a large extent, and the electrode heals.
INTRODUCTION Global energy challenges have driven automotive manufactures to improve the fuel economy of personal transportation vehicles; at the same time, electrochemical energy storage technologies have continued to improve in terms of performance and cost
1-4
. Figure 1 below
Range
Energy (Watt-hr / kg) Maximum stored energy per unit of battery mass
EV EREV PHEV
Power (Watt / kg)
Acceleration
Maximum power per unit of battery mass
Figure 1. Ragone plot showing (a) various electrochemical energy storage technologies, (b) approximate vehicle requirements (EV, PHEV, and EREV refer to electric vehicle, plug-in hybrid electric vehicle, and extended range electric vehicle, respectively), and (c) the evolutionary trend over time, yielding increased power and energy density.
indicates the progress that has been made in recent years relative to battery technology. Figure 2 depicts a propulsion strategy commensurate with the increased use of electrified vehicles and renewable fuel sources. Existing primary concerns associated with lithium ion batteries and high-volume traction applications are associated with costs, life (cycle and calendar), and performance over a wide temperature range. Despite these concerns, it is well recognized that lithium ion batteries will soon be used in a variety of electrified vehicles, spanning from engine start/stop applications to hybrid electric vehicles to pure electric vehicles. Hence,
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