Spinel Cathode Valence Control for High-Voltage Stability
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Solution Overview
Problem
Current secondary battery active materials face challenges in achieving both high charge and discharge capacity and extended battery life, particularly at high electromotive forces, due to issues with trivalent manganese instability and valence changes affecting discharge capacity and structural stability.
Innovation Solution
The development of an active material represented by the formula Li(a1)(Ni(x1)Mn(2-x1-y1-z1)O4), where 0.4 ≤ x1 ≤ 0.6, 0 < y1, 0 < z1, and x1 + y1 + z1 < 2, with M1 being Si or Ti and M2 being Li, B, Na, or Ca, which enhances crystallinity and life characteristics by controlling valence changes and improving energy density.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If trivalent Mn is replaced by another element to improve structural stability, then reliability is improved, but discharge capacity decreases
Solution Approach 1:
The patent changes the valence state parameter of manganese from trivalent to tetravalent in the spinel structure LiNi0.5Mn1.5O4, enabling operation at higher potentials (4.5V or more vs Li/Li+) while maintaining structural stability through the specific composition ratio that prevents Jahn-Teller distortion
Solution Approach 2:
The patent creates a composite spinel structure combining Ni, Mn, and Li in specific ratios (LiNi0.5Mn1.5O4) where Ni provides high potential through divalent-to-tetravalent valence change while Mn maintains structural stability, achieving both high capacity and reliability
2Use of energy by moving object
If part of Mn is replaced by Ni, Co, Fe, Cu, Cr to increase charge and discharge potential, then energy density increases, but life characteristics deteriorate
Solution Approach 1:
The patent optimizes the composition parameters within the spinel structure to achieve LiNi0.5Mn1.5O4 stoichiometry, where the specific Ni:Mn ratio enables high potential operation while the spinel crystal structure maintains stability during cycling, resolving the contradiction between energy density and battery life
Solution Approach 2:
The patent assigns specific functional roles to different elements in the spinel structure: Ni sites provide high potential through valence changes while Mn sites maintain structural stability, creating local functional differentiation that achieves both high energy density and long cycle life
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
This solution provides a secondary battery with improved life characteristics, high energy density, and the ability to operate at high voltage, reducing the number of series in assembled batteries and extending battery life while maintaining equivalent energy density.
Implementation Method 1
when the average valence of Mn ions changes between trivalent and tetravalent, Jahn-Teller distortion occurs in the crystal and the stability of the crystal structure decreases
Implementation Method 2
LiMn2O4 undergoes the valence change of Mn shown in the following formula with charge and discharge
Data Source
Figure 1
AI summary
An active material for a secondary battery with improved life characteristics is provided. An active material for a secondary battery according to this exemplary embodiment is an active material for a secondary battery represented by Lia1(Nix1Mn2-x1-y1-z1M1y1M2z1)O4 wherein 0 < x1, 0 < y1, 0 < z1, x1 + y1 + z1 < 2, and 0 ≤ a1 ≤ 2; M1 is at least one selected from Si and Ti; and M2 is at least one selected from Li, B, Mg, Na, K, and Ca. In addition, an active material for a secondary battery according to this exemplary embodiment is an active material for a secondary battery represented by Lia2(Nix2Mn2-x2-y2-z2M3y2M4z2)O4 wherein 0 < x2, 0 < y2, 0 < z2 < 0.03, x2 + y2 + z2 < 2, and 0 ≤ a2 ≤ 2; M3 is at least one selected from Si and Ti; and M4 is at least one selected from Li, B, Mg, Al, Na, K, and Ca, and includes at least Al.