Fabrication of All-Solid-State Lithium Polymer Secondary Batteries Using Al₂O₃-Coated LiCoO₂

Abstract

Lithium secondary batteries are being researched and developed worldwide to realize ubiquitous energy storage devices from mobile phones to electric vehicles. 1 For cathode active materials, one of the most important components in such batteries, a high capacity and a high operation voltage are required for a high energy density. However, current commercially available batteries using a layered LiCoO 2 cathode material suffer from a relatively small capacity, because only half of the Li ions in LiCoO 2 can be extracted reversibly. 2 It was previously observed that, once more than half of the lithium ions were removed from a LiCoO 2 structure in a high-voltage region (>4.2 V), the cycle performance severely degenerated in a liquid organic system. Recently, Dahn et al. and Cho et al. reported an inorganic oxide (e.g., Al 2 O 3 , ZrO 2 ) coating of a cathode with a view to improve its reversibility at a high cathode potential for lithium secondary batteries using an organic electrolyte solution. [3][4][5][6][7][8] The charge-discharge performance in a highvoltage region can be improved by stabilizing the cathode surface. Moreover, for instance, in the case of using a LiCoO 2 cathode, because the number of mobile lithium ions increases with an increase in upper cutoff voltage, high-capacity batteries can be realized. However, to our knowledge, the mechanism of improvement still requires further investigation. For example, Cho et al. claimed that coating oxides serve as a mechanical constraint that prevents the Li x CoO 2 lattice from a large volume change during a chargedischarge reaction in a high-voltage region. On the other hand, Chen and Dahn suggested that the poor cycle performance of noncoated LiCoO 2 is caused by impedance growth due to some side reactions and that an inorganic oxide coating that modifies surface properties of cathode materials suppresses impedance growth.An all-solid-state lithium polymer secondary battery (LPB) that uses a polyether-based solid polymer electrolyte (SPE) as a fundamentally safe battery system has been investigated by many researchers. 9-14 As SPEs do not contain a volatile organic electrolyte solution, the fabrication of large-scaled

A Strategy to Make High Voltage LiCoO2Compatible with Polyethylene Oxide Electrolyte in All-Solid-State Lithium Ion Batteries

“…Some inorganic coating materials, such as Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 , Li 3 PO 4 , and Al 2 O 3 , acting as an oxidation barrier for PEO electrolyte, have displayed significant improvement to the LiCoO 2 /PEO interface z E-mail: cuigl@qibebt.ac.cn at high voltage above 4.4 V vs. Li/Li + . [10][11][12][13] But, element interdiffusion at the inorganic coating materials and LiCoO 2 interface is usually inevitable during high temperature sintering process. Moreover, the reported inorganic coating materials are feeble to remarkably improve the cycling stability of LiCoO 2 /PEO/Li all-solid-state batteries.…”

Vapor-assisted synthesis of Al2O3-coated LiCoO2 for high-voltage lithium ion batteries

“…On the one hand, there is doping with metal elements, for instance, Al [6], Mg [7][8][9], Cu [10], Zr [9], Ti [11], and La [12]. On the other hand, there is coating with oxides, such as MgO [3], CeO 2 [13], Fe 2 O 3 [14], ZrO 2 [15][16][17][18][19], TiO 2 [20,21], ZnO [22], and Al 2 O 3 [4,[23][24][25]. The coating layer can greatly improve the capacity retention during cycling by reducing changes in the lattice parameters and decreasing cobalt dissolution.…”

“…Hajime Miyashiro and his co-workers [25] improved the performance of LiCoO 2 by coating with Al 2 O 3 , but the capacity retention was only 68.0% after 100 cycles (voltage window: 4.4-3.0 V). Herein, we report a feasible method of coating the surface of LiCoO 2 with a homogeneous alumina membrane by vapor-assisted hydrolysis.…”

All solid-state lithium polymer secondary batteries using spinel Li4/3Ti5/3O4 as an active material

“…And among these studies, most of the efforts have been devoted to investigate the electrochemical performance with Li|SPE|cathode constructions where cathode indicates positive electrode with higher redox potential than roughly ∼3.0 V vs. Li + /Li. Miyashiro and Kobayashi et al reported the significant improvements of cycle performance of LPBs by using the techniques of ceramic coating onto cathode surface [5][6][7][8][9]. We recently reported the electrochemical properties of LPB with Li|SPE|LiFePO 4 construction in which ionic conductivity of SPE films was improved by adding plasticizers of tris(methoxy polyethylenglycol) borate ester (B-PEG) and tris(methoxy polyethylenglycol) aluminate ester (Al-PEG) [10][11][12][13].…”