Improved Electrochemical Performance of Li[sub 2]MnSiO[sub 4]/C Composite Synthesized by Combustion Technique

Abstract

Li 2 MnSiO 4 cathode powders were synthesized by a simple combustion technique using citric acid as a chelating agent. The as-synthesized powder was ballmilled with acetylene black ͑0-20 wt %͒ and heated at 700°C in argon atmosphere to form a Li 2 MnSiO 4 /C composite. X-ray powder diffraction indicated the formation of Li 2 MnSiO 4 possessing an orthorhombic crystal structure along with manganese oxide as a minor impurity phase. Field-emission-scanning electron microscopy showed that pristine Li 2 MnSiO 4 consists of large agglomerates of ϳ500 to 800 nm. The addition of acetylene black resulted in a drastic change in morphology for Li 2 MnSiO 4 /C composites consisting of uniform grains of ϳ50 nm. The electrochemical discharge capacity as well as the rate capability of Li 2 MnSiO 4 also improved dramatically with an increasing amount of conducting carbon ͑acetylene black͒ in the matrix, and a value as high as 164 mAh g −1 was obtained at a current density of 0.01 mA/cm 2 . Impedance spectroscopy showed that the addition of acetylene black decreases the charge-transfer impedance and checks the growth of cell impedance during cycling. Cyclic voltammetry showed two oxidation/reduction couples at 3.6/2.9 and 4.5/4.3 V with good reversibility. Rechargeable lithium-ion batteries are the most advanced battery systems among the contemporary energy storage technologies in terms of accessible energy density, reversibility, and cycle life. It is presently used in virtually all electronic devices and is projected as the power source for electric vehicles. However, the conventional cathode materials, namely, LiCoO 2 , LiMn 2 O 4 , and LiFePO 4 , suffer from one or more problems related to structural stability, rate capability, energy density, etc.

Charge/discharge characteristics of Jahn–Teller distorted nanostructured orthorhombic and monoclinic Li2MnSiO4cathode materials

“…LMS material has an advantage over LFS because of relatively easier deintercalation process and thus may provide higher specic capacity at higher cell voltage, and higher energy density than that of LFS material system. [11][12][13] With all these advantages, LMS system suffers from various disadvantages such as poor electronic conductivity, low lithium diffusion coefficient and poor electrochemical performance.…”

Fast sol–gel synthesis of mesoporous Li2MnSiO4/C nanocomposite with improved electrochemical performance for lithium-ion batteries

“…Thus the cycling performance of the material is also quite poor. To overcome the obstacles, particle size minimization and surface carbon coating were employed to accommodate the strains, buffer the particle expansions and improve the electronic conductivity of Li 2 MnSiO 4 [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26].…”

“…Till now, the preparation methods including sol-gel method [12,13,[15][16][17][18][19][20][21][22][23][24], solid-state reaction [25,26], and microwave-solvothermal process [14] have been employed to synthesize the nano-sized Li 2 MnSiO 4 /C composite. The electrochemical performances of the composites have been improved to some extent.…”

“…Due to homogenous mix of reactants and easy control of stoichiometry [27], the sol-gel synthesis is the most popular method for preparing Li 2 MnSiO 4 /C nanocomposite [12,13,[15][16][17][18][19][20][21][22][23][24]. Usually, two kinds of silicon sources, SiO 2 nanoparticle and tetraethyl orthosilicate (TEOS), are employed to prepare the gel precursor for Li 2 MnSiO 4 /C nanocomposite.…”

“…TEOS is also a kind of silicon source that can generate the precursor gel of SiO 2 for the preparation of Li 2 MnSiO 4 in situ. In this case, the reactant solution is normally heated over 60°C to accelerate the hydrolysis of TEOS to silanols and the condensation of silanols [13,[19][20][21][22][23][24]. The heating process is time-consuming and will possibly cause the unfavorable growth of the colloidal particles.…”