Spinel Cathode Composition for High-Temperature Cycle Stability
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Solution Overview
Problem
Spinel-type lithium-manganese-containing composite oxides exhibit low cycle performance under high temperatures, limiting their application due to structural instability and side reactions, particularly with hydrofluoric acid in the electrolyte.
Innovation Solution
A positive active material is developed by doping spinel-type lithium-manganese-containing composite oxides with elements such as V, Nb, Ta, Mo, W, Ru, Te, or Tl, and combining them with elements like Si, S, or Cl to form a polyoxyanion, which stabilizes the structure and captures hydrofluoric acid, enhancing cycle performance and structural stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If spinel-type lithium-manganese-containing composite oxide is used as positive active material, then theoretical capacity is high, but cycle performance under high temperature is low
Solution Approach 1:
The patent modifies the chemical composition parameters of the spinel-type lithium-manganese-containing composite oxide by controlling the ratios of Li, Mn, and other metal elements (such as Ni, Co, Al, Mg, Ca, Sr, Ba) to optimize both capacity and stability. The molecular formula Li1+x-a-bMn2-a-bO4-t with controlled deviations in stoichiometry allows tuning of electrochemical properties to maintain high capacity while improving high-temperature cycle performance.
Solution Approach 2:
The patent creates a composite material system by incorporating multiple metal elements into the spinel structure. The positive active material comprises Li-Mn-O spinel phase combined with other metal oxides or hydroxides (Ni, Co, Al, Mg, Ca, Sr, Ba), forming a multi-element composite that synergistically improves both capacity characteristics and structural stability at elevated temperatures.
2Use of energy by moving object
If spinel-type lithium-manganese-containing composite oxide is used, then capacity characteristics are good, but structural stability under high temperature is poor
Solution Approach 1:
The patent adjusts compositional parameters including the Li excess parameter x, Mn deficiency parameters a and b, and oxygen deficiency parameter t to optimize the spinel structure. By controlling these parameters within specific ranges, the material achieves enhanced structural stability at high temperature while preserving good capacity characteristics through optimized lithium diffusion pathways and electronic structure.
Solution Approach 2:
The patent forms a composite structure where the spinel-type Li-Mn-O phase is combined with other metal oxides or hydroxides (Ni, Co, Al, Mg, Ca, Sr, Ba). This composite approach creates a more robust crystal structure with higher thermal stability, preventing Jahn-Teller distortion and phase transitions that occur in pure LiMn2O4 at elevated temperatures, while maintaining electrochemical activity.
3Use of energy by moving object
If spinel-type lithium-manganese-containing composite oxide is used, then theoretical capacity is high, but cycle life under high temperature is short
Solution Approach 1:
The patent optimizes stoichiometric parameters (x, a, b, t in Li1+x-a-bMn2-a-bO4-t) to enhance long-term stability during cycling. The controlled deviations from ideal stoichiometry create a more stable crystal structure that resists degradation during repeated charge-discharge cycles at high temperature, thereby extending cycle life while maintaining high capacity utilization.
Solution Approach 2:
The multi-element composite structure (Li-Mn-Ni-Co-Al-Mg-Ca-Sr-Ba-O) provides enhanced structural robustness during cycling. The presence of multiple stabilizing elements suppresses structural transformations and surface reactions that typically limit cycle life at elevated temperatures, enabling the material to maintain its capacity characteristics over extended cycling periods.
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 doped material improves the cycle storage performance and cycle life of secondary batteries under high temperatures by stabilizing the spinel structure and reducing side reactions, leading to enhanced structural stability and capacity characteristics.
Implementation Method 1
A is a doping element for a manganese site of the spinel-type lithium-manganese-containing composite oxide
Implementation Method 2
M is used for combining with O to form a second phase containing a polyoxylanion
Implementation Method 3
the positive active material can form a more stable oxyfluoride that contains elements A and M... protect the entire battery system
Implementation Method 4
The element X in this embodiment of this application can increase an average valence state of manganese and a manganese-site element in the spinel structure
Implementation Method 5
a positive active material provides lithium ions that shuttle between a positive electrode and a negative electrode during charging and discharging
Data Source
AI summary
A positive active material, a secondary battery, a battery module, a battery pack, and an electrical device are disclosed. The positive active material includes a spinel-type lithium-manganese-containing composite oxide with a molecular formula of Li1+xAaMbXcMn2−a−b−c−xO4−t. In the molecular formula: A is a doping element for a manganese site of the spinel-type lithium-manganese-containing composite oxide; M is used for combining with O to form a second phase containing a polyoxyanion, and M includes one or more of B, C, N, Si, P, S, or Cl; X includes one or more of Mg, Al, Si, Ca, Sc, Ti, Cr, Fe, Co, Ni, Cu, Zn, or Zr; and the molecular formula satisfies: −0.1≤x≤0.3, 0<a≤0.2, 0<b≤0.2, 0<c≤0.7, and 0≤t≤0.2.