Enhancing High-Voltage Performance of Ni-Rich Cathode by Surface Modification of Self-Assembled NASICON Fast Ionic Conductor LiZr₂(PO₄)₃

Abstract

Coating methodology is commonly employed in the enhancement of Ni-rich cathodes for Li-ion batteries as an efficient approach, while its strategy and effect are still great challenges to achieve success in surface modifications for comprehensive electrochemical properties. In this work, the surface of Ni-rich cathode LiNi0.82Co0.15Al0.03O2 (NCA) is modified by intimately coating NASICON-type solid electrolyte LiZr2(PO4)3 (LZP) via a facile approach involving electrostatic attraction. With well-designed architecture and a uniform NASICON-type LZP nanolayer wrapping over the NCA microsphere, the entire electrode demonstrates exceptional Li+ diffusion and conductivity and suppresses the side reaction between electrolyte and electroactive NCA, stabilizing the phase interface with less Li+/Ni2+ cation mixing. As a result, the NCA@LZP can deliver a high reversible capacity of 182 mAh g–1 at 1C in 2.7–4.3 V, maintaining the capacity retention of 84.6% after 100 cycles. More importantly, the structure stability of NCA is enhanced substantially by surface modification of LZP at high cutoff voltage. It achieves a reversible capacity of 204 mAh g–1 and keeps 100.4 mAh g–1 after 500 cycles at 1C in the potential range of 2.7–4.5 V. This effective strategy of using NASICON fast ionic conductor like LZP as a coating layer may provide a new insight to modify the surface of Ni-rich electrode, improving the rate capability and cyclic performance under high voltage.

In Situ Surface Modification for Improving the Electrochemical Performance of Ni‐Rich Cathode Materials by Using ZrP2O7

“…[34] Moreover,t he percentage of absorbed oxygen (89.76 %) after coating is lower than that of the pristine material( 91.30 %), determined by using Avantage software. It is provedt hat the contento fr esidual lithium salt is reduced: Li 4 P 2 O 7 [16] and LiZr 2 (PO 4 ) 3 [18] could be generatedd uring the process of ZrP 2 O 7 formation. The bond dissociation energies (DH f298 ,k J À1 mol À1 )o fe ach atom with Oa toms were reported to be CoÀO( 368.0), NiÀO( 391.6), MnÀO( 402), PÀO( 596.6), ZrÀO( 760.0), [35] and strong covalent bonds can increase the chemicals tabilityo ft he coating material andi nhibit the attack of HF in the electrolyte, whicht hen improves the electrochemical performance of the NCM811.…”

“…[11] Single layer or multilayer coatings are formed on the surface of the material, whichc an transfer electrons or ions and protect the cathode from electrolyte corrosion. [12] Metal oxides or other polyanion materials such as Al 2 O 3 , [13] LaPO 4 , [14] TiP 2 O 7 , [15] Li 4 P 2 O 7 , [16] Li 3 PO 4 /PPy, [17] LiZr 2 (PO 4 ) 3 , [18] Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 , [19,20] Al 2 O 3 /LiAlO 2 , [21] and MoS 2 [22] have been reported to be very effective coating materials. Li et al [23] reported Zr modificationh ad dual functions, one is that Zr 4 + can enter into the lattice of the transition metal plane or lithium plane, the other is that the remaining Zr 4 + floats on the surface of particles, formed aL i 2 ZrO 3 coating layer.…”

Surface/Interface Structure Degradation of Ni‐Rich Layered Oxide Cathodes toward Lithium‐Ion Batteries: Fundamental Mechanisms and Remedying Strategies

“…Now that the parasitic side reactions start from the interfaces between the solid cathodes and liquid electrolytes, the most effective method is to avoid their direct contact by introducing passive physical protection layer on the cathode surface . In general, the employed coating species can be categorized into i) the chemically and electrochemically inactive coatings, including metal oxides (Al 2 O 3 , TiO 2 , MgO, SiO 2 , ZrO 2 , V 2 O 5 , Nb 2 O 5 , ZnO, MoO 3 , and Y 2 O 3 ,) and phosphates (AlPO 4 , MnPO 4 , Mn 3 (PO 4 ) 2 , La(PO 4 ) 3 , Ni 3 (PO 4 ) 2 , Co 3 (PO 4 ) 2 , ZrP 2 O 7 , and FePO 4 ) as well as some fluorides (AlF 3 and LiF); ii) the Li + conductive coatings, mainly refer to the Li‐containing compounds such as LiAlO 2 , Li 2 ZrO 3 , Li 3 VO 4 , Li 2 MnO 3 , LiMn 2 O 4 , Li 3 PO 4 (LPO), LiFePO 4 (LFP), LiMnPO 4 , Li 2 TiO 3 , LiTiO 2 , Li 2 O‐2B 2 O 3 , LiTi 2 (PO 4 ) 3 , LiZr 2 (PO 4 ) 3 , Li 1.4 Al 0.4 Ti 1.6 (PO 4 ) 3 , Li 0.5 La 0.5 TiO 3 , LiTaO 3 , Li 4 SiO 4 , and LiAlF 4 as well as some heterostructured electrochemical active cathodes (Li 1.2 Ni 0.2 Mn 0.6 O 2 , Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O 2 and NCM333); and iii) the electron conducting coating, representatively, reduced graphene oxide (rGO), permeable poly (3,4‐ethylenedioxythiophene) (PEDOT),…”

Surface Modification Strategies for Improving the Cycling Performance of Ni‐Rich Cathode Materials

“…Residual lithium compounds (see section 4) have an adverse effect on the electrochemical performance because of their intrinsically low ionic conductivity and subsequent decomposition accompanied by gassing. Some coatings can convert these residuals into reasonably conductive lithium compounds, such as phosphates, and garnets, thereby improving the rate capability. It has been claimed that polymeric coatings, which generally achieve full surface coverage more readily, can prevent cracking by giving elastic support to the secondary particles , .…”