Nongraphitic carbon microbeads were prepared by hydrothermal treatment o
f a glucose aqueous solutionat 180
![](/images/entities/deg.gi<font color=)
f">C. Impregnation o
f glucose-derived carbon microbeads with citric acid was used to control themicrobeads' sur
face and electrochemical properties. The microspherical sample thus obtained exhibiteda highly disordered nanocrystalline structure and a low BET sur
face area. The electrochemical per
formanceo
f carbon microbeads was evaluated
from discharge/charge experiments in lithium and sodium cells, aswell as
from electrochemical impedance spectroscopy measurements. The intercalation o
f Li and Na insur
face-modi
fied carbon microbeads was explored by EPR and NMR spectroscopy. It was shown thatsimilar mechanisms operate
for lithium and sodium insertion into disordered carbons. The observed Curie-like behavior and the change in intensity o
f the EPR signals as a
function o
f cell voltage agreed wellwith lithium insertion into di
fferent sites o
f disordered carbon structures
forming paramagnetic centers.Microspherical carbon samples with high reversible capacities in both Li and Na cells commonly exhibitlow concentrations o
f paramagnetic centers.