title: Stabilized lithium-ion battery anode performance by calcium-bridging of two dimensional siloxene layers.
abstract: A Ca-bridged siloxene (Ca-siloxene) composed of two-dimensional siloxene planes with Ca bridging was synthesized via a solid state metathesis reaction using TaCl5to extract Ca from CaSi2. Three different Ca-siloxenes synthesized at Cl2/Ca molar ratios of 0.25, 1.25 and 2.5 (CS0.25, CS1.25 and CS2.5, respectively) were fabricated and investigated as anode active materials for lithium-ion batteries. Both secondary and primary Ca-siloxene particles, which serve to increase the contact interfaces with conductive materials and to generate accessible sites for lithium ions, respectively, were found to become smaller and to have increased pore volumes as the Cl2/Ca molar ratio was increased. These Ca-siloxenes exhibited stable charge/discharge performance as anode materials, with 69-99% capacity retention after 50 charge/discharge cycles (compared with 36% retention for a conventional Kautsky-type siloxene). The charge capacity also increased with increases in the Cl2/Ca molar ratio, such that the CS2.5 showed the highest capacity after 50 charge/discharge cycles. This may reflect the formation of Si6Li6rather than SiLi4.4and suggests the maintenance of layered Si planes for large capacity retention after charge/discharge cycling. The increase of contact interfaces between acetylene black (as a conductive material) and Ca-siloxenes was found to effectively increase the lithium-ion capacity of Ca-siloxene during high rate charge/discharge cycling.
authors.affiliation: Toyota Central R&D Labs., Inc., Nagakute, Aichi, 480-1192 Japan. e1152@mosk.tytlabs.co.jp.
authors.forename: Haruo
authors.identifier: http://orcid.org/0000-0002-8933-8301
authors.initials: H
authors.lastname: Imagawa
authors.affiliation: Toyota Central R&D Labs., Inc., Nagakute, Aichi, 480-1192 Japan. e1152@mosk.tytlabs.co.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Itahara