Optimizing Both Bulk and Surface Structure of Li‐Rich Layered Cathodes for Long‐Life and Safe Li‐Ion Batteries

Abstract

Although oxygen redox in Li‐rich layered cathodes can boost the available capacity over 250 mAh g−1, it also brings a rapid capacity fade upon long‐term cycling and serious safety issue during thermal abuse. To circumvent these problems, an integrated strategy via interlayer regulation at surface and the delocalization of Li2MnO3‐like domain on bulk is proposed. The controllable interlayer by atomic layer deposition can maximize the coating effects on elimination of the lattice mismatch to inhibit the structural degradation during cycling. And the delocalized Li2MnO3‐like domain through compositional control can fully prohibit lattice oxygen release from the bulk to improve the thermal stability of electrode. The optimized cathode material exhibits a capacity retention of 94.0% after 200 cycles. A 1.25 Ah multilayer pouch cell with the cathode and graphite anode delivers an outstanding cycling performance that retains 80.4% of its capacity at 0.5 C after 710 cycles. More importantly, the distinguished safety features derived from the method are verified after successfully passing practical‐level thermal safety and nail penetration test.

Dependence of Initial Capacity Irreversibility on Oxygen Framework Chemistry in Li‐Rich Layered Cathode Oxides

“…Despite inferior to dynamic limits, the irreversible reactions also need to be investigated comprehensively due to its important influence for cycling performance. [44,45] Generally, three factors are proposed to be responsible for the undesirable irreversible reactions: 1) generation of instable CEI layer; [9] 2) surface structural reconstruction due to TM migration; [6,46] 3) irreversible oxygen loss from cathode materials. [18] Although oxygen redox is believed to be a dominating contribution for the excessive capacity of Li-rich materials, the inevitable irreversible oxygen loss, which mainly exists in the form of O 2 gas and CO 2 gas release, can result in the capacity decay.…”

Improved Cycling Stability of Ni-Rich Cathode Material by In Situ Introduced TM-B-O Amorphous Surface Structure

“…Further improving energy density is the developing theme and trend of power batteries. − Lithium-ion batteries (LIBs) are currently the best power choice due to the comprehensive performances and will still be the mainstream in future for a long time. − The main route to significantly increase specific energy for power LIBs is through the development of new cathode materials with higher voltage and greater capacity. − Among the layered ternary cathode materials (LiNi x Co y Mn 1– x – y O 2 , NCM), the Ni-rich families with the component of Ni above 80% show obvious advantages in energy density. The energy density of the assembled batteries can be significantly enhanced using these materials matching with appropriate anodes and electrolytes.…”

Electrochemical In Situ Na Doping to Construct High-Performance Lithium-Rich Cathode

“…1 In order to achieve long-range and lightweight of new energy vehicles, LIBs need to develop toward high energy density and low cost, where the cathode material is an important factor limiting their development. 2 Currently, transition metal (TM) redox based layered cathode materials are approaching the energy density limits. TM redox (TAR) and oxygen anion redox (OAR) of lithium-rich layered oxides provide high specific capacities (>250 mA h g −1 ), but irreversible OAR reactions cause sluggish kinetics and persistent voltage decay under long cycles, severely hindering their commercial application.…”

“…The rapid development of electric vehicles and large energy storage grids has raised the demand for more advanced lithium-ion batteries (LIBs) . In order to achieve long-range and lightweight of new energy vehicles, LIBs need to develop toward high energy density and low cost, where the cathode material is an important factor limiting their development . Currently, transition metal (TM) redox based layered cathode materials are approaching the energy density limits.…”