In this study, Li1.2Mn0.54Ni0.13Co0.13O2 as lithium-ion battery cathode active material was prepared by a sol–gel method. The effects of chelating agents including three different kinds of chelating agents (citric acid, glycolic acid, and polyvinyl pyrrolidone) on its performance were studied. X-ray diffraction tests were carried out to explore the samples’ structure, showing α-NaFeO2 structure with \(R - \bar 3m\) space group for all the samples. After various kinds of tests, the sample prepared with citric acid showed the worst properties among the three samples. The sample prepared with polyvinyl pyrrolidone has the smallest size (200–350 nm), with uniform distribution and smooth surfaces. Electrochemical tests show that it has the highest initial discharge capacity (231 mAh g−1) and initial charge/discharge efficiency (70.9%). Electrical impedance spectroscopy confirms that its low charge-transfer resistance is responsible for the superior discharge capacity and rate performance. Furthermore, the sample prepared with polyvinyl pyrrolidone could improve its cycle performance after coating with 3% graphene; its capacity retention is up to 89.8% after 100 cycles at 1 C rate. The sample prepared with glycolic acid achieved the best cycling stability. The discharge capacity was decreased from 150 to 138 mAh g−1, and the capacity retention rate was as high as 91.7% after 100th cycle under a current of 1 C.Open image in new window

LiNi0.9Co0.05Mn0.025Mg0.025O2 was prepared by a sol–gel method using citric acid as a chelating agent. Calcination temperature and calcination time played a critical role in the preparation of the materials, and their effects on the properties of the materials were discussed in detail. The optimal calcination temperature and time were determined to be 700 °C and 12 h, respectively. The sample prepared under the above optimal conditions had a well ordered hexagonal layered structure. The charge–discharge tests showed that the initial capacities of the sample were 201.0 mA h g−1 and 187.6 mA h g−1 at the discharge rate of 0.1 C and 1 C between 2.8 and 4.3 V, respectively. The capacity retention ratio was 99.3% at 0.1 C after 10 cycles and 91.86% at 1 C after 50 cycles. The excellent rate capability of the sample prepared at the optimal conditions was also observed.

Electrochemically active carbon (EAC) was modified with In and In(OH)3 respectively. Its properties were characterized by TEM, EDS and XRD, and its hydrogen evolution behaviour and effects on the cycle life of valve-regulated lead-acid (VRLA) batteries were investigated. The study found that the modification of EAC with In or In(OH)3 did not significantly influence the crystal structure and surface morphology of EAC, but it can effectively increase the overpotential of hydrogen evolution and decrease the evolution rate of hydrogen on EAC. It is also observed that the addition of EAC modified with an appropriate amount of In or In(OH)3 in the negative plates of VRLA batteries can remarkably decrease the evolution rate of hydrogen and prolong the cycle life of batteries under high-rate partial-state-of-charge conditions. Moreover, in comparison with EAC modified with In, EAC modified with In(OH)3 showed better performance in terms of the improved cycle life of batteries.

In order to inhibit sulfation and hydrogen evolution of the negative plates and to prolong the cycle life of valve-regulated lead-acid batteries for hybrid-electric vehicles, electrochemically active carbon (EAC) and Indium (III) oxide (In2O3) are added into negative active materials of valve-regulated lead-acid batteries. The influences of EAC and In2O3 on the cycle performance of valve-regulated lead-acid batteries are investigated under high-rate partial-state-of-charge conditions. Experiment results indicate that addition of EAC in negative active materials can prolong the high-rate partial-state-of-charge cycle performance of valve-regulated lead-acid batteries, whilst it results in the accelerated evolution rate of hydrogen during charge process. It is also observed that EAC with an appropriate amount of In2O3 can effectively increase the overpotential of hydrogen evolution, which can not only produce the decreased hydrogen evolution rate and promote conversion of PbSO4 to Pb in capacity recovery process, but also prolong the high-rate partial-state-of-charge cycle life of valve-regulated lead-acid batteries. The battery added with 0.5% EAC and 0.02% In2O3 in negative active materials exhibits at least four times longer cycle life than that without In2O3.Highlights► EAC in NAM prolongs the cycle life of VRLA batteries during HRPSoC operation. ► Appropriate addition of In2O3 in EAC can decrease the evolution rate of hydrogen. ► Appropriate addition of In2O3 and EAC in NAM can promote conversion of PbSO4 to Pb. ► 0.02% In2O3 in NAM significantly prolongs the cycle life of VRLA batteries.

A solid film was prepared by electrodepositing on a gold-film-coated quartz crystal electrode in Na2FeO4 solution, and characterized in 1 M LiClO4/propylene carbonate (PC) + 1, 2-dimethoxyethane (DME; 1:1 by volume) electrolyte using electrochemical quartz crystal microbalance (EQCM). The EQCM experimental and X-ray photoelectron spectroscopy results indicate that the composition of the electrodeposited solid film prepared in the potential range of 0.18 to −0.57 V vs. Ag/AgCl is FeOOH; and almost 1 mol lithium ions can be intercalated into and then extracted from 1 mol FeOOH film during discharge/charge process in 1 M LiClO4/PC + DME electrolyte. The discharge/charge experiment indicates that the specific capacity of FeOOH film stabilizes at a value close to its theoretical specific capacity after 20 cycles, and FeOOH film maintains a specific capacity of about 300 mAh g−1 at the end of 170 cycles. It is therefore concluded that the FeOOH film has a good electrochemical cycle ability in 1 M LiClO4/PC + DME electrolyte.