Study of the effect of different synthesis routes on Li extraction–insertion from LiCoPO4

Abstract

The electrochemical performance of LiCoPO 4 -based electrodes was studied in dependence on synthetic conditions. The role of particle size distribution is illustrated. Structural changes occurring at lithium extraction-insertion was explored by ex-situ and in-situ synchrotron XRD measurements. For the samples annealed at temperature lower than 600°C the amorphisation of the cathode material was identified. For a high-temperature sample the two-phase character of electrochemical reaction was confirmed. The character of structural changes observed at charge and discharge is different: the two-phase reaction LiCoPO 4 -"CoPO 4 " occurs during charging, while discharge induces a strong increase of the cell volume for the Li-poor phase. KeywordsPhospho-olivine, lithium batteries, in situ diffraction, synchrotron * Corresponding author of lithium deinsertion from LiMnPO 4 and LiCoPO 4 seems to take place also [9][10][11][12]. According to Li et al., the second phase arising by the lithium extraction from lithium manganese phosphate has a composition Li x MnPO 4 , where x is very close to zero [9]. Recently, Delacourt et al. showed that the electrochemical delithiation of LiMnPO 4 , prepared by a new precipitation route, leads to the disappearing of pristine LiMnPO 4 and to the formation of the new phase with the same structure, but with lower cell volume (302 Å 3 and 275 Å 3 , respectively) [10]. The authors suggest that the appearing phase is MnPO 4 .Previously, we have shown that LiCoPO 4 -samples prepared by solid-state reaction at high temperature demonstrate unsatisfactory electrochemical performance [13]. The reversibility of

Carbonate anion controlled growth of LiCoPO4/C nanorods and its improved electrochemical behavior

“…A c c e p t e d M a n u s c r i p t 4 studied LiMPO 4 (M = Fe, Co, Mn, Ni) cathodes [9][10][11][12]. Despite these advantages, there are challenges associated with the practical application of LiCoPO 4 [9,10,[13][14][15][16] such as poor conductivity and slow lithium transport kinetics.…”

“…Despite these advantages, there are challenges associated with the practical application of LiCoPO 4 [9,10,[13][14][15][16] such as poor conductivity and slow lithium transport kinetics. These must be improved if LiCoPO 4 is to be a suitable cathode material alternative.…”

“…While coating carbon on the pristine LiFePO 4 surface is quite straightforward, the same is not true for the LiCoPO 4 counterpart [17]; strong contact between the LiCoPO 4 particles is not created. Among the few reports of the preparation of LiCoPO 4 cathode [7,9,10,13,15,18,19], Wolfenstine et al [13] have observed the simultaneous formation of cobalt phosphide (Co 2 P) when LiCoPO 4 is produced in the inert heating environment. The highly conducting (~10 -1 S cm -1 ) Co 2 P phase formation yields better electrochemical performance of the LiCoPO 4 cathode [13].…”

Doping LiMnPO4 with Cobalt and Nickel: A First Principle Study

“…However, severe kinetic problems during cycling and low electronic and ionic conductivity have prevented its application so far [11]. Moreover, the other possible candidate materials-namely, LiNiPO 4 and LiCoPO 4 -suffer, respectively, from the lack of suitable electrolytes (as the redox potential of the Ni 2+ /Ni 3+ couple is 5.1 V [12]) and from low energy density and high capacity fading with the current electrolytes and organic solvents [13]. The substitution of cations like Mn, Fe, Ni, and Co in a single olivine structure is one of the most popular approaches to improving the ionic and electronic conductivity of the materials.…”

Electrochemical and Magnetic Studies of Li-Deficient Li1-xCo1-xFexPO4Olivine Cathode Compounds

“…23 However, this LiFePO 4 cathode is not suitable to attain the highenergy density batteries described above, because its voltage is insufficiently high. Many studies have been carried out on other olivine compounds such as LiMnPO 4 [33][34][35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52] and its utilization enables us to attain highenergy density batteries. Many strategies for the LiCoPO 4 cathode, similar to those of the LiFePO 4 cathode, have been proposed, because they present common problems that hinder their practical application: particle fining, [39][40][41] carbon coating of the particle surface, [42][43][44][45][46] and the cation substitution.…”