5 research outputs found
Enhanced Interfacial Kinetics and High-Voltage/High-Rate Performance of LiCoO<sub>2</sub> Cathode by Controlled Sputter-Coating with a Nanoscale Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> Ionic Conductor
The
selection and optimization of coating material/approach for
electrode materials have been under intensive pursuit to address the
high-voltage induced degradation of lithium ion batteries. Herein,
we demonstrate an efficient way to enhance the high-voltage electrochemical
performance of LiCoO<sub>2</sub> cathode by postcoating of its composite
electrode with Li<sub>4</sub>Ti<sub>5</sub>O<sub>12</sub> (LTO) via
magnetron sputtering. With a nanoscale (∼25 nm) LTO coating,
the reversible capacity of LiCoO<sub>2</sub> after 60 cycles is significantly
increased by 40% (to 170 mAh g<sup>–1</sup>) at room temperature
and by 118% (to 139 mAh g<sup>–1</sup>) at 55 °C. Meanwhile,
the electrode’s rate capability is also greatly improved, which
should be associated with the high Li<sup>+</sup> diffusivity of the
LTO surface layer, while the bulk electronic conductivity of the electrode
is unaffected. At 12 C, the capacity of the coated electrode reaches
113 mAh g<sup>–1</sup>, being 70% larger than that of the uncoated
one. The surface interaction between LTO and LiCoO<sub>2</sub> is
supposed to reduce the space-charge layer at the LiCoO<sub>2</sub>–electrolyte interface, which makes the Li<sup>+</sup> diffusion
much easier as evidenced by the largely enhanced diffusion coefficient
of the coated electrode (an order of magnitude improvement). In addition,
the LTO coating layer, which is electrochemically and structurally
stable in the applied potential range, plays the role of a passivation
layer or an artificial and friendly solid electrolyte interface (SEI)
layer on the electrode surface. Such protection is able to impede
propagation of the in situ formed irreversible SEI and thus guarantee
a high initial columbic efficiency and superior cycling stability
at high voltage
Multistep Lithiation of Tin Sulfide: An Investigation Using <i>in Situ</i> Electron Microscopy
Two-dimensional (2D) metal sulfides
have been widely explored as
promising electrodes for lithium-ion batteries since their two-dimensional
layered structure allows lithium ions to intercalate between layers.
For tin disulfide, the lithiation process proceeds <i>via</i> a sequence of three different types of reactions: intercalation,
conversion, and alloying, but the full scenario of reaction dynamics
remains nebulous. Here, we investigate the dynamical process of the
multistep reactions using <i>in situ</i> electron microscopy
and discover the formation of an intermediate rock-salt phase with
the disordering of Li and Sn cations after initial 2D intercalation.
The disordered cations occupy all the octahedral sites and block the
channels for intercalation, which alter the reaction pathways during
further lithiation. Our first-principles calculations of the nonequilibrium
lithiation of SnS<sub>2</sub> corroborate the energetic preference
of the disordered rock-salt structure over known layered polymorphs.
The <i>in situ</i> observations and calculations suggest
a two-phase reaction nature for intercalation, disordering, and following
conversion reactions. In addition, <i>in situ</i> delithiation
observation confirms that the alloying reaction is reversible, while
the conversion reaction is not, which is consistent with the <i>ex situ</i> analysis. This work reveals the full lithiation
characteristic of SnS<sub>2</sub> and sheds light on the understanding
of complex multistep reactions in 2D materials
Multistep Lithiation of Tin Sulfide: An Investigation Using <i>in Situ</i> Electron Microscopy
Two-dimensional (2D) metal sulfides
have been widely explored as
promising electrodes for lithium-ion batteries since their two-dimensional
layered structure allows lithium ions to intercalate between layers.
For tin disulfide, the lithiation process proceeds <i>via</i> a sequence of three different types of reactions: intercalation,
conversion, and alloying, but the full scenario of reaction dynamics
remains nebulous. Here, we investigate the dynamical process of the
multistep reactions using <i>in situ</i> electron microscopy
and discover the formation of an intermediate rock-salt phase with
the disordering of Li and Sn cations after initial 2D intercalation.
The disordered cations occupy all the octahedral sites and block the
channels for intercalation, which alter the reaction pathways during
further lithiation. Our first-principles calculations of the nonequilibrium
lithiation of SnS<sub>2</sub> corroborate the energetic preference
of the disordered rock-salt structure over known layered polymorphs.
The <i>in situ</i> observations and calculations suggest
a two-phase reaction nature for intercalation, disordering, and following
conversion reactions. In addition, <i>in situ</i> delithiation
observation confirms that the alloying reaction is reversible, while
the conversion reaction is not, which is consistent with the <i>ex situ</i> analysis. This work reveals the full lithiation
characteristic of SnS<sub>2</sub> and sheds light on the understanding
of complex multistep reactions in 2D materials
Multistep Lithiation of Tin Sulfide: An Investigation Using <i>in Situ</i> Electron Microscopy
Two-dimensional (2D) metal sulfides
have been widely explored as
promising electrodes for lithium-ion batteries since their two-dimensional
layered structure allows lithium ions to intercalate between layers.
For tin disulfide, the lithiation process proceeds <i>via</i> a sequence of three different types of reactions: intercalation,
conversion, and alloying, but the full scenario of reaction dynamics
remains nebulous. Here, we investigate the dynamical process of the
multistep reactions using <i>in situ</i> electron microscopy
and discover the formation of an intermediate rock-salt phase with
the disordering of Li and Sn cations after initial 2D intercalation.
The disordered cations occupy all the octahedral sites and block the
channels for intercalation, which alter the reaction pathways during
further lithiation. Our first-principles calculations of the nonequilibrium
lithiation of SnS<sub>2</sub> corroborate the energetic preference
of the disordered rock-salt structure over known layered polymorphs.
The <i>in situ</i> observations and calculations suggest
a two-phase reaction nature for intercalation, disordering, and following
conversion reactions. In addition, <i>in situ</i> delithiation
observation confirms that the alloying reaction is reversible, while
the conversion reaction is not, which is consistent with the <i>ex situ</i> analysis. This work reveals the full lithiation
characteristic of SnS<sub>2</sub> and sheds light on the understanding
of complex multistep reactions in 2D materials
Multistep Lithiation of Tin Sulfide: An Investigation Using <i>in Situ</i> Electron Microscopy
Two-dimensional (2D) metal sulfides
have been widely explored as
promising electrodes for lithium-ion batteries since their two-dimensional
layered structure allows lithium ions to intercalate between layers.
For tin disulfide, the lithiation process proceeds <i>via</i> a sequence of three different types of reactions: intercalation,
conversion, and alloying, but the full scenario of reaction dynamics
remains nebulous. Here, we investigate the dynamical process of the
multistep reactions using <i>in situ</i> electron microscopy
and discover the formation of an intermediate rock-salt phase with
the disordering of Li and Sn cations after initial 2D intercalation.
The disordered cations occupy all the octahedral sites and block the
channels for intercalation, which alter the reaction pathways during
further lithiation. Our first-principles calculations of the nonequilibrium
lithiation of SnS<sub>2</sub> corroborate the energetic preference
of the disordered rock-salt structure over known layered polymorphs.
The <i>in situ</i> observations and calculations suggest
a two-phase reaction nature for intercalation, disordering, and following
conversion reactions. In addition, <i>in situ</i> delithiation
observation confirms that the alloying reaction is reversible, while
the conversion reaction is not, which is consistent with the <i>ex situ</i> analysis. This work reveals the full lithiation
characteristic of SnS<sub>2</sub> and sheds light on the understanding
of complex multistep reactions in 2D materials