Nickel-Rich Cathode Doping and Coating for Interface Stability
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Solution Overview
Problem
The increase in nickel content in ternary positive electrode materials leads to decreased thermal stability, lattice oxygen evolution, internal cracks, electrolyte ingress, transition metal dissolution, and poor interface stability, affecting the performance and safety of lithium-ion batteries.
Innovation Solution
A positive electrode material with a chemical formula Li a Ni x Co y Mn 1-x-y M b O 2-c Q c, doped with high-valence cations (Mo 6+<, Sb 5+<, Zr 4+<, Ti 4+<, Nb 5+<, W 6+<, Y 5+<, Ta 5+< ) and anions (S 2-<, Se 2-<, Te 2-<, P 3-< ) to stabilize the bulk structure and interface, combined with a selenium-containing substance coating to react with residual lithium compounds and form a protective electrolyte interface, and a conductive polymer coating to inhibit side reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the nickel content in ternary positive electrode materials is increased to improve energy density, then the reversible capacity and energy density are improved, but the thermal stability of the materials decreases
Solution Approach 1:
The patent applies local quality by introducing high-valence cations (such as Mo6+, W6+, Nb5+) specifically at the surface region of the nickel-rich ternary positive electrode material particles. This creates a compositional gradient where the surface has different chemical characteristics than the bulk, providing localized thermal stability enhancement without compromising the high nickel content core that delivers high energy density. The surface-modified region acts as a protective layer while the interior maintains high capacity.
Solution Approach 2:
The patent creates a composite structure by combining nickel-rich ternary material (NCM or NCA) with high-valence cation-containing compounds (such as MoO3, WO3, Nb2O5) through a surface modification process. This composite approach integrates the high capacity benefits of nickel-rich materials with the thermal stability benefits of high-valence cation compounds, resolving the contradiction between energy density and thermal stability.
2Use of energy by moving object
If the nickel content is increased to improve energy density, then the reversible capacity is improved, but lattice oxygen evolution and internal cracks occur leading to electrolyte ingress and transition metal dissolution
Solution Approach 1:
The patent applies preliminary anti-action by pre-modifying the surface of nickel-rich positive electrode material with high-valence cations before the material is assembled into a battery. This pre-treatment creates a protective surface layer that prevents lattice oxygen evolution and suppresses internal crack formation during subsequent charge-discharge cycles. By addressing the harmful effects before they occur, the patent maintains reversible capacity while preventing oxygen release and associated degradation mechanisms.
Solution Approach 2:
The high-valence cation surface modification acts as a cushioning layer that absorbs and mitigates the harmful effects of lattice oxygen evolution and internal stress accumulation. This protective layer prevents direct contact between the electrolyte and the nickel-rich material surface, thereby preventing transition metal dissolution and electrolyte decomposition that would otherwise occur during high-voltage operation.
3Use of energy by moving object
If the nickel content is increased to improve energy density, then the capacity is improved, but surface residual lithium compounds form causing poor interface stability and side reactions
Solution Approach 1:
The patent applies preliminary action by performing surface modification with high-valence cations before the positive electrode material is assembled into a battery. This pre-modification step forms a stable surface layer that prevents the formation of residual lithium compounds (RLCs) during initial battery cycling. By addressing the surface chemistry beforehand, the patent eliminates the need for extended formation cycles and prevents interface instability issues that would otherwise develop during battery operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances the cycling stability, high-temperature storage performance, and rate capability of lithium-ion batteries by stabilizing the bulk structure, reducing side reactions, and preventing electrolyte oxidation, while maintaining electrochemical performance.
Implementation Method 1
a positive electrode material, the positive electrode material having the following chemical formula: Li a Ni x Co y Mn 1-x-y M b O 2-c Q c wherein 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M comprises a high-valence cation, Q comprises an anion
Implementation Method 2
The selenium-containing substance can react with residual lithium compounds (RLCs) on the surface of the nickel-rich positive electrode material to form a CEI such as lithium selenoselenate (Li 2 Se 2 O 3 ) and lithium selenate (Li 2 SeO 4 ) in situ
Implementation Method 3
a second coating layer which is coated on a surface of the first coating layer and comprises a conductive polymer
Data Source
Figure 1
AI summary
A positive electrode material. The positive electrode material has the following chemical formula: LiaNixCoyMn1-x-yMbO2-cQc, wherein 0.2≤a≤1.2, x≥0.6, y>0, b>0, c>0, M comprises a high-valence cation, and Q comprises an anion. By doping a high-valence cation and an anion in a nickel-rich ternary positive electrode material, the bulk structure of the nickel-rich ternary positive electrode material under lithium deintercalation is stabilized, side reactions, lattice oxygen evolution and transition metal dissolution are reduced, and the cycling stability, the high-temperature storage performance and the rate capability are improved. In addition, the outer surface of the positive electrode material can be further coated with a selenium-containing substance coating layer (2), a selenium-containing substance in the selenium-containing substance coating layer (2) can react with residual lithium compounds on the surface of the positive electrode material, and the remaining selenium-containing substances can be combined with lattice oxygen released in a high-delithiation state to prevent an electrolyte solution from being oxidized. Moreover, a conductive substance coating layer (3) can be further prepared on the outer surface of the selenium-containing substance coating layer (2), thereby preventing direct contact between the selenium-containing substance and the electrolyte solution, and inhibiting side reactions.