Researchers from Oak Ridge National Laboratory have demonstrated a solid-state high-voltage (5 V) lithium battery with an extremely long cycle life of more than 10,000 cycles, with 90% capacity retention. The solid electrolyte enables the use of high-voltage cathodes and Li anodes with minimum side reactions, leading to a high Coulombic efficiency of 99.98+%.
|ORNL solid-state Li-ion battery. Click to enlarge.
A paper on their work is published in the journal Advanced Energy Materials.
The energy stored in a battery of a given size is proportional to its voltage. Conventional lithium-ion batteries use organic liquid electrolytes that have a maximum operating voltage of 4.3 V; operation above this limit can cause short cycle life and serious safety concerns.
However, lithium-ion-conducting solid electrolytes could enable high-energy battery chemistries by circumventing safety issues of conventional lithium batteries with liquid electrolytes. Use of a solid electrolyte would simplify the use of a Li-metal anode with its high gravimetric energy density, for example.
Toyota, for one, is working on all-solid-state batteries as a mid-term advanced battery solution. (Earlier post.)
However, achieving the required combination of high ionic conductivity and a broad electrochemical window in solid electrolytes is a grand challenge for the synthesis of battery materials, members of the ORNL team noted in a paper published in the Journal of the American Chemical Society in 2013. (Earlier post.)
In this latest study, the Oak Ridge team replaced the conventional liquid electrolyte with a ceramic solid electrolyte of lithium phosphorus oxynitride (Lipon), and used a LiNi0.5Mn1.5O4 cathode and Li anode at a charge voltage to 5.1V. The solid state battery retained more than 90% of its original capacity after 10,000 cycles—equivalent to more than 27 years of life with a daily charge/discharge cycle.
|Voltage profiles of the (a) LiNi0.5Mn1.5O4 solid-state lithium battery and (b) a LiNi0.5Mn1.5O4 liquid battery discharged at different rates. The battery was charged at C/10 before each discharge measurement. Li et al.Click to enlarge.
Juchuan Li, Cheng Ma, Miaofang Chi, Chengdu Liang, and Nancy J. Dudney (2014) “Solid electrolyte: the key for high-voltage lithium batteries,” Advanced Energy Materials doi: 10.1002/aenm.201401408