LiFePO₄ is considered to be one of the most promising cathode materials for lithium ion batteries for electric vehicle (EV) application. However, there are still a number of unsolved issues regarding the influence of Li and Fe-site substitution on the physicochemical properties of LiFePO₄. This is a review-type article, presenting results of our group, related to the possibility of the chemical modification of phosphoolivine by introduction of cation dopants in Li and Fe sublattices. Along with a synthetic review of previous papers, a large number of new results are included. The possibility of substitution of Li⁺ by Al³⁺, Zr⁴⁺, W⁶⁺ and its influence on the physicochemical properties of LiFePO₄ was investigated by means of XRD, SEM/EDS, electrical conductivity and Seebeck coefficient measurements. The range of solid solution formation in Li_1−3xAl_xFePO₄, Li_1−4xZr_xFePO₄ and Li_1−6xW_xFePO₄ materials was found to be very narrow. Transport properties of the synthesized materials were found to be rather weakly dependent on the chemical composition. The battery performance of selected olivines was tested by cyclic voltammetry (CV). In the case of LiFe_1−yM_yPO₄ (M = Mn, Co and Ni), solid solution formation was observed over a large range of y (0 < y ≤ 1). An increase of electrical conductivity for the substitution level y = 0.25 was observed. Electrons of 3d metals other than iron do not contribute to the electrical properties of LiFe_1−yM_yPO₄, and substitution level y > 0.25 leads to considerably lower values of σ. The activated character of electrical conductivity with a rather weak temperature dependence of the Seebeck coefficient suggests a small polaron-type conduction mechanism. The electrochemical properties of LiFe_1−yM_yPO₄ strongly depend on the Fe substitution level.

A 4.5 V “dual carbon” LIC device is constructed based on all nitrogen doped graphene nanostructures. It could achieve an ultrahigh energy density of 187.9 W h kg⁻¹ at a high power density of 2250 W kg⁻¹ due to the alleviating kinetic mismatch.

A new method of synthesis of stoichiometric Na₂FeM(SO₄)₃ (M = Fe, Mn, Ni) materials is developed.

Composite polymer electrolytes provide an emerging solution for new battery development by replacing liquid electrolytes, which are commonly complexes of polyethylene oxide (PEO) with ceramic fillers. However, the agglomeration of fillers and weak interaction restrict their conductivities. By contrast with the prevailing methods of blending preformed ceramic fillers within the polymer matrix, here we proposed an in situ synthesis method of SiO₂ nanoparticles in the PEO matrix. In this case, robust chemical interactions between SiO₂ nanoparticles, lithium salt and PEO chains were induced by the in situ non-hydrolytic sol gel process. The in situ synthesized nanocomposite polymer electrolyte delivered an impressive ionic conductivity of ~1.1 × 10⁻⁴ S cm⁻¹ at 30 °C, which is two orders of magnitude higher than that of the preformed synthesized composite polymer electrolyte. In addition, an extended electrochemical window of up to 5 V vs. Li/Li⁺ was achieved. The Li/nanocomposite polymer electrolyte/Li symmetric cell demonstrated a stable long-term cycling performance of over 700 h at 0.01–0.1 mA cm⁻² without short circuiting. The all-solid-state battery consisting of the nanocomposite polymer electrolyte, Li metal and LiFePO₄ provides a discharge capacity of 123.5 mAh g⁻¹, a Coulombic efficiency above 99% and a good capacity retention of 70% after 100 cycles.

New stoichiometric Li-rich layered oxides (xLi₂MnO₃·(1-x)LiMn_0.5Ni_0.25Co_0.25O₂ or Li[Li_yMn_1-y-2zNi_zCo_z]O₂) were proposed as high-energy density cathode materials for Li-ion batteries. The correlation between chemical composition of the materials and their structural as well as electrochemical performances is discussed. It was found that all synthesized materials crystalize within C2/m space group with existence of superstructure and possess nanometric spherical-shaped morphology. The analysis of the charge/discharge tests shows that Li[Li_0.2Mn_0.6Ni_0.1Co_0.1]O₂ electrode delivers nearly 350 mAh·g⁻¹ for the first discharge process and 250 mAh·g⁻¹ for following cycles. The investigation of the kinetics of the electrode reactions by means of CV and EIS methods confirmed that Li[Li_0.2Mn_0.6Ni_0.1Co_0.1]O₂ exhibits highest lithium diffusion coefficients, what with obtained electrochemical cycling tests suggest optimal chemical composition of this material ensuring high energy density along with long-term endurance.