4 research outputs found
Printed pH Sensors for Textile‐Based Wearables: A Conceptual and Experimental Study on Materials, Deposition Technology and Sensing Principles
Solution-gel-based surface modification of <tex>LiNi_{0.5}Mn_{1.5}O_{4-\u3b4}$</tex> with amorphous Li-Ti-O coating
Abstract: LNMO (LiNi0.5Mn1.5O4-delta) is a high-energy density positive electrode material for lithium ion batteries. Unfortunately, it suffers from capacity loss and impedance rise during cycling due to electrolyte oxidation and electrode/electrolyte interface instabilities at high operating voltages. Here, a solution-gel synthesis route was used to coat 0.5-2.5 mu m LNMO particles with amorphous Li-Ti-O (LTO) for improved Li conduction, surface structural stability and cyclability. High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) analysis coupled with energy dispersive X-ray (EDX) showed Ti-rich amorphous coatings/islands or Ti-rich spinel layers on many of the LTO-modified LNMO facets, with a thickness varying from about 1 to 10 nm. The surface modification in the form of amorphous islands was mostly possible on high-energy crystal facets. Physicochemical observations were used to propose a molecular mechanism for the surface modification, combining insights from metalorganic chemistry with the crystallographic properties of LNMO. The improvements in functional properties were investigated in half cells. The cell impedance increased faster for the bare LNMO compared to amorphous LTO modified LNMO, resulting in R-ct values as high as 1247 Omega (after 1000 cycles) for bare LNMO, against 216 Omega for the modified material. At 10C, the modified material boosted a 15% increase in average discharge capacity. The improvements in electrochemical performance were attributed to the increase in electrochemically active surface area, as well as to improved HF-scavenging, resulting in the formation of protective byproducts, generating a more stable interface during prolonged cycling
Polymeric Backbone Eutectogel Electrolytes for High-Energy Lithium-Ion Batteries
This work introduces a polymeric backbone eutectogel
(P-ETG) hybrid
solid-state electrolyte with an N-isopropylacrylamide
(NIPAM) backbone for high-energy lithium-ion batteries (LIBs). The
NIPAM-based P-ETG is (electro)chemically compatible with commercially
relevant positive electrode materials such as the nickel-rich layered
oxide LiNi0.6Mn0.2Co0.2O2 (NMC622). The chemical compatibility was demonstrated through (physico)chemical
characterization methods. The nonexistence (within detection limits)
of interfacial reactions between the electrolyte and the positive
electrode, the unchanged bulk crystallographic composition, and the
absence of transition metal ions leaching from the positive electrode
in contact with the electrolyte were demonstrated by Fourier transform
infrared spectroscopy, powder X-ray diffraction, and elemental analysis,
respectively. Moreover, the NIPAM-based P-ETG demonstrates a wide
electrochemical stability window (1.5–5.0 V vs Li+/Li) and a reasonably high ionic conductivity at room temperature
(0.82 mS cm–1). The electrochemical compatibility
of a high-potential NMC622-containing positive electrode and the P-ETG
is further demonstrated in Li|P-ETG|NMC622 cells, which deliver a
discharge capacity of 134, 110, and 97 mAh g–1 at
C/5, C/2, and 1C, respectively, after 90 cycles. The Coulombic efficiency
is >95% at C/5, C/2, and 1C. Hence, gaining scientific insights
into
the compatibility of the electrolytes with positive electrode materials
that are relevant to the commercial market, like NMC622, is important
because this requires going beyond the electrolyte design itself,
which is essential to their practical applications