Designing the Charge Storage Properties of Li‐Exchanged Sodium Vanadium Fluorophosphate for Powering Implantable Biomedical Devices

Abstract

The growing demand for bioelectronics has generated widespread interest in implantable energy storage. These implantable bioelectronic devices, powered by a complementary battery/capacitor system, have faced difficulty in miniaturization without compromising their functionality. This paper reports on the development of a promising high‐rate cathode material for implantable power sources based on Li‐exchanged Na1.5VOPO4F0.5 anchored on reduced graphene oxide (LNVOPF‐rGO). LNVOPF is unique in that it offers dual charge storage mechanisms, which enable it to exhibit mixed battery/capacitor electrochemical behavior. In this work, electrochemical Li‐ion exchange of the LNVOPF structure is characterized by operando X‐ray diffraction. Through designed nanostructuring, the charge storage kinetics of LNVOPF are improved, as reflected in the stored capacity of 107 mAh g−1 at 20C. A practical full cell device composed of LNVOPF and T‐Nb2O5, which serves as a pseudocapacitive anode, is fabricated to demonstrate not only high energy/power density storage (100 Wh kg−1 at 4000 W kg−1) but also reliable pulse capability and biocompatibility, a desirable combination for applications in biostimulating devices. This work underscores the potential of miniaturizing biomedical devices by replacing a conventional battery/capacitor couple with a single power source.

Multiscale factors in designing alkali-ion (Li, Na, and K) transition metal inorganic compounds for next-generation rechargeable batteries

“…In Na 1.5 VOPO 4 F 0.5 system, (a) Rate performance of with different size of particle and (b) in situ XRD results of micronbrick and nanoparticle. 350 (c) in situ XRD measurement result of 40 nm particle size of LiFePO 4 during galvanostatic charge/discharge at C/40. 351 It shows solid solution structural variation.…”

“…host material for Na 350,355 and K 356 ) are also applied. In the case of Na 1.5 VOPO 4 F 0.5 system, for example, Lai et al 350 reported that among the various particle sizes including micronbrick, nanobrick, and nanoparticle, the smallest nanoparticle expectedly delivers superior rate performance with high capacity (Fig. 28a).…”

“…28b). 350 The micro-scale stress within the particles, which can be originated from the local ion concentration gradient change, is also a performance degradation factor similar to intergranular crack, 339 therefore, solid solution behavior can lessen the cyclic mechanical damages because it can avoid spatial heterogeneities. However, not all the materials show enhanced battery performance by lowering particle sizes, and to fully take advantages, several prerequisites have to be met, e.g., the particles must be in good contact through an effective connection network within the electrode, 224,360,361 side reactions should be inconspicuous or mitigated via adequate engineering, etc.…”

Recent Advances in High‐Performance Microbatteries: Construction, Application, and Perspective

“…As far as powering capability is concerned, MB for implantable bioelectronics is generally in pursuit of high volumetric energy density and stable cycling life, thus material design with biocompatibility being the key part. Recently, Dunn and co-workers [161] reported a promising cathode material with a mixed battery/capacitor electrochemical behavior. By anchoring Na 1.5 VOPO 4 F 0.5 on rGO, the cathode composed by nanoparticles exhibited a solid solution process during the charge storage behavior.…”

“…When the biocompatibility is concerned, an MTS assay is just a validation process while a living body implantation is needed to further Reproduced with permission. [161] Copyright 2019, Wiley-VCH. c) Schematic illustrations of MB implanted in the dorsal subcutaneous region of the SD rat.…”