An Approach towards Synthesis of Nanoarchitectured LiNi1/3Co1/3Mn1/3O2Cathode Material for Lithium Ion Batteries

Tin dioxide-based nanomaterials as anodes for lithium-ion batteries

The development of new electrode materials for lithium-ion batteries (LIBs) has attracted significant attention because commercial anode materials in LIBs, like graphite, may not be able to meet the increasing energy demand of new electronic devices. Tin dioxide (SnO2) is considered as a promising alternative to graphite due to its high specific capacity. However, the large volume changes of SnO2 during the lithiation/delithiation process lead to capacity fading and poor cycling performance. In this review, we have summarized the synthesis of SnO2-based nanomaterials with various structures and chemical compositions, and their electrochemical performance as LIB anodes. This review addresses pure SnO2 nanomaterials, the composites of SnO2 and carbonaceous materials, the composites of SnO2 and transition metal oxides, and other hybrid SnO2-based materials. By providing a discussion on the synthesis methods and electrochemistry of some representative SnO2-based nanomaterials, we aim to demonstrate that electrochemical properties can be significantly improved by modifying chemical composition and morphology. By analyzing and summarizing the recent progress in SnO2 anode materials, we hope to show that there is still a long way to go for SnO2 to become a commercial LIB electrode and more research has to be focused on how to enhance the cycling stability.

Direct surface coating of high voltage LiCoO2 cathode with P(VDF-HFP) based gel polymer electrolyte

For high-voltage cycling of lithium-ion batteries, a gel polymer Li-ion conductor layer, P(VDF-HFP)/LiTFSI (PHL) with high electrochemical stability has been coated on the surfaces of as-formed LiCoO₂ (LCO) cathodes by a solution-casting technique at low temperature. An LCO cathode coated with around 3 μm thickness of the PHL ultrathin membrane, retains 88.4% of its original capacity (184.3 mA h g⁻¹) after 200 cycles in the 3.0–4.6 V range with a standard carbonate electrolyte, while the non-coated one retains only 80.4% of its original capacity (171.5 mA h g⁻¹). The reason for the better electrochemical behaviors and high-voltage cycling is related to the distinctive characteristics of the PHL coating layer that is compact, has highly-continuous surface coverage and penetrates the bulk of LCO, forming an integrated electrode. The PHL coating layer plays the role of an ion-conductive protection barrier to inhibit side reactions between the charged LCO surface and electrolyte, reduces the dissolution of cobalt ions and maintains the structural stability of LCO. Further, the PHL coated LCO cathode is well preserved, compared to the uncoated one which is severely cracked after 200 cycles at a charging cut-off voltage of 4.6 V.

For high-voltage cycling of lithium-ion batteries, a Li-ion conductor layer, P(VDF-HFP)/LiTFSI with high electrochemical stability has been coated on the surfaces of as-formed LiCoO₂ cathodes by a solution casting technique at low temperature.

High-Ni cathode material improved with Zr for stable cycling of Li-ion rechargeable batteries

The Zr solvent solution method, which allows primary and secondary particles of LiNi_0.90Co_0.05Mn_0.05O₂ (NCM) to be uniformly doped with Zr and simultaneously to be coated with an Li₂ZrO₃ layer, is introduced in this paper. For Zr doped NCM, which is formed using the Zr solvent solution method (L-NCM), most of the pinholes inside the precursor disappear owing to the diffusion of the Zr dopant solution compared with Zr-doped NCM, which is formed using the dry solid mixing method from the (Ni_0.90Co_0.05Mn_0.05)(OH)₂ precursor and the Zr source (S-NCM), and Li₂ZrO₃ is formed at the pinhole sites. The mechanical strength of the powder is enhanced by the removal of the pinholes by the formation of Li₂ZrO₃ resulting from diffusion of the solvent during the mixing process, which provides protection from cracking. The coating layer functions as a protective layer during the washing process for removing the residual Li. The electrochemical performance is improved by the synergetic effects of suitable coatings and the enhanced structural stability. The capacity-retentions for 2032 coin cells are 86.08%, 92.12%, and 96.85% at the 50^th cycle for pristine NCM, S-NCM, and L-NCM, respectively. The superiority of the liquid mixing method is demonstrated for 18 650 full cells. In the 300^th cycle in the voltage range of 2.8–4.35 V, the capacity-retentions for S-NCM and L-NCM are 77.72% and 81.95%, respectively.

The Zr solvent solution method, which allows primary and secondary particles of LiNi_0.90Co_0.05Mn_0.05O₂ (NCM) to be uniformly doped with Zr and simultaneously to be coated with an Li₂ZrO₃ layer, is introduced in this paper.