Batteries power much of our modern day life – from our phones, laptop computers, cars and may other devices we use every day and take for granted.
Yet the lifespan of current battery technology is disappointingly short – at best giving us a few years of reliable service and at worst catching fire or even exploding. Apart from the obvious inconvenience of our devices running out of power, this short lifespan creates major environmental issues with the need to source increasingly large amounts of raw materials, and the disposal of growing mountains of defunct batteries.
Much of our current battery technology is based on lithium-ion technology. Electrochemical lithium insertion and extraction often severely alters the electrode crystal chemistry, and this contributes to degradation with electrochemical cycling. Moreover, electrodes do not act in isolation, and this can be difficult to manage, especially in all-solid-state batteries. Therefore, discovering materials that can reversibly insert and extract large quantities of the charge carrier (Li+), that is, high capacity, with inherent stability during electrochemical cycles is necessary.
In a recent paper published in Nature Materials (Konuma, I., Goonetilleke, D., Sharma, N. et al. A near dimensionally invariable high-capacity positive electrode material. Nat. Mater. (2022).) the authors examined lithium-excess vanadium oxides with a disordered rocksalt structure as high-capacity and long-life positive electrode materials.
Nanosized Li8/7Ti2/7V4/7O2 in optimized liquid electrolytes delivered a large reversible capacity of over 300 mAh g−1 with two-electron V3+/V5+ cationic redox, reaching 750 Wh kg−1 versus metallic lithium.
Critically, highly reversible Li storage and no capacity fading for 400 cycles were observed in all-solid-state batteries with a sulfide-based solid electrolyte. X-ray diffraction combined with high-precision dilatometry reveals excellent reversibility and a near dimensionally invariable character during electrochemical cycling, which is associated with reversible vanadium migration on lithiation and delithiation.
This work demonstrates an example of an electrode/electrolyte couple that produces high-capacity and long-life batteries enabled by multi-electron transition metal redox with a structure that is near invariant during cycling.
In plain English, in future batteries based on this technology could have an almost infinite life, extending the useful life of our devices and reducing the need to mine new materials or dispose of old worn-out batteries!