Li-Rich Mn-Ni Cathode Composition for Voltage Decay Control
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Solution Overview
Problem
Current Lithium Manganese Rich (LMR) positive electrode active materials face issues such as voltage decay during cycling, decreased rate capability, and poor cycle performance, which affect the overall efficiency and capacity of lithium-ion batteries.
Innovation Solution
Optimized LMR compositions with controlled lithium, manganese, nickel, and cobalt ratios, represented by formulas Li1.04 to 1.06Mn0.52 to 0.53Ni0.41 to 0.44-xMxO2, where M is Co, Cr, or a combination thereof, with 0<x≤0.1, to enhance electronic and ionic conductivity and improve cycle performance and rate capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional LMR compositions are used to achieve high gravimetric energy density, then energy density is improved, but voltage decay during cycling and poor cycle performance occur
Solution Approach 1:
The patent modifies the chemical composition parameters of LMR materials by precisely controlling the ratios of lithium, manganese, nickel, and dopant elements (x ranging from 0.01 to 0.05 in formula Li1+xMn0.5Ni0.4-yMxO2). This parameter optimization resolves the contradiction by achieving both high energy density and improved cycle performance through balanced oxidation states and enhanced structural stability.
Solution Approach 2:
The patent creates composite LMR materials by combining multiple elements (Li, Mn, Ni, Co, Cr, Al, or Ti) in specific ratios. This composite approach resolves the contradiction by synergistically combining the high capacity of Ni-rich phases with the structural stability of Mn-rich phases and the stabilizing effect of dopant elements, achieving both high energy density and good cycle performance.
2Quantity of substance
If LMR compositions are used to increase capacity, then specific capacity is improved, but rate capability decreases
Solution Approach 1:
The patent optimizes compositional parameters (x and y values in the formula) to balance capacity and rate capability. By controlling the dopant concentration and elemental ratios, the material achieves enhanced ionic and electronic conductivity, allowing high specific capacity (>200 mAh/g) to be maintained even at high discharge rates.
Solution Approach 2:
The patent introduces local compositional variations through doping with Co, Cr, Al, or Ti at specific sites within the crystal structure. This local quality modification creates regions with enhanced conductivity and structural stability that facilitate fast ion transport while maintaining high overall capacity, thus resolving the contradiction between capacity and rate capability.
3Use of energy by moving object
If LMR compositions are used to achieve high energy density, then energy density is improved, but voltage decay during cycling occurs
Solution Approach 1:
The patent creates a composite structure combining Ni-rich layers (providing high capacity) with Mn-rich and dopant-containing layers (providing structural stability). This composite architecture resolves the contradiction by spatially separating the functions of high capacity and voltage stability, allowing the material to maintain both high energy density and voltage stability during cycling.
Solution Approach 2:
The patent incorporates dopant elements (Co, Cr, Al, Ti) in advance to preemptively stabilize the crystal structure against degradation. This beforehand cushioning effect prevents Jahn-Teller distortion and structural collapse that would otherwise cause voltage decay, allowing the material to maintain stable voltage output throughout its cycle life while delivering high energy density.
Data Source
AI summary
A positive electrode active material may include a compound represented by the formula Li1.04 to 1.06Mn0.52 to 0.53Ni0.41 to 0.44-xMxO2, where M represents cobalt, chromium, or a combination thereof, and x ranges from 0 to 0.1. The average oxidation state of manganese is controlled between 3.8 and 4.0. The average oxidation state of nickel is controlled to be 2.0. A battery may contain the positive electrode.