Crystal structural design of exposed planes: express channels, high-rate capability cathodes for lithium-ion batteries

Abstract

Developing high-performance lithium ion batteries (LIBs) requires optimization of every battery component. Currently, the main problems lie in the mismatch of electrode capacities, especially the excessively low capacity of cathodes compared with that of anodes. Due to the anisotropy of the crystal structure, different crystal planes play different roles in the transmission of lithium ions. Among these, the {010} facets of layered-structure materials, the (110) planes of spinel cathodes and the (010) planes of olivine cathodes can provide open surface structures, which furnish express channels for the rapid and efficient transmission of lithium ions, leading to enhanced rate performance. However, due to the high-energy surfaces of these crystal planes, they tend to disappear in the synthetic process, forming thermodynamic equilibrium products dominated by low-energy and electrochemically-inactive planes. From the structure design of the material itself, preparing functional materials with specific morphologies and crystal structures is considered to be the most effective way to improve the cyclability and rate performance of LIB cathodes. In this review, we highlight the latest developments in selectively exposing the crystal planes of LIB cathode materials. The synthetic method, the corresponding electrochemical performance, especially the rate capability, and the growth mechanism have been systematically summarized for layered-structure cathodes of LiCoO2, LiNixCoyMn1-x-yO2 and Li2MnO3·LiMO2, spinel cathodes of LiMn2O4 and LiNi0.5Mn1.5O4, and olivine cathodes of LiFePO4. This in-depth discussion and understanding is beneficial for the rational design of well-performing LIB cathodes and can provide direction and perspectives for future work.

Challenges and Strategies to Advance High‐Energy Nickel‐Rich Layered Lithium Transition Metal Oxide Cathodes for Harsh Operation

“…In addition to the phase structures and elemental composition, it has been found that the morphologies of Ni-rich cathodes especially the surface structures of the primary particles significantly affect the lithium intercalation kinetics. [126] The layered lithium transition metal oxide cathodes exhibited typical α-NaFeO 2 structure, in which lithium ions and TM cations occupy the octahedral sites of oxygen framework, forming a structure consisting of alternately stacked layers of MO 6 and LiO 6 octahedra. As shown in Figure 27, each layered perpendicular to the c axis is called (001) plane, which is electrochemically inactive due to the closely packed structure.…”

Experimental and Theoretical Study of LiMn2O4 Synthesized by the Solution Combustion Method Using Corn Starch as Fuel

“…The particle size and microstructure infer a better charge capacity of the sample treated at 500 °C in relation to the sample treated at 700 °C because the sample at 500 °C presents pores and less sintering (greater surface area), thus facilitating the interface process associated with lithium diffusion. 58,59,65 It should be noted that recent works 13,58,59 report the importance of the preparation of LiMn 2 O 4 with specific morphologies, such as high porosity. In these works, the preparations involve several steps to obtain materials with the desired properties.…”

“…The crystalline structure of LiMn 2 O 4 as well as the shape and size of the crystallites and grains are correlated with its electrochemical features. [11][12][13] The spinel LiMn 2 O 4 structure consists of compact cubic close packing composed by oxygen atoms that form 32 octahedral sites and 64 tetrahedral sites, as shown in Figure 1. 11 The Mn 3+ and Mn 4+ ions occupy the octahedral sites, whereas the Li + ion occupies the tetrahedral sites or the empty octahedral sites.…”

“…Additionally, the crystal structure also presents vacancies and interstices that allow the charge compensation through the oxidative state variation of the Mn cation. [11][12][13][14][15][16] These sites are important in the oxidation and reduction processes, due to the charge compensation of the Mn x+ cation (x = 3 or 4) in the channel. The Jahn-Teller effect, due to the insertion/removal lithium processes, is associated with low cycling current.…”

Multiscale factors in designing alkali-ion (Li, Na, and K) transition metal inorganic compounds for next-generation rechargeable batteries

“…open surface of {010} facets for layered, (110) planes for spinel, (010) planes for olivine facilitate the ion diffusion). 366 (ii) Surface area in the secondary particle: It has pros and cons. Large surface area leads to higher reaction rates, but can promote undesirable electrode/electrolyte reaction.…”