Lithium-Sodium Manganese Cathode Doping for Stable High-Capacity Cycling
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Solution Overview
Problem
Lithium-rich manganese-based positive electrode materials suffer from low initial efficiency, low specific capacity, poor cycling performance, and high gas evolution, limiting their development and application in batteries.
Innovation Solution
A lithium-sodium composite manganese-based material is developed, where sodium is doped at lithium sites, transition metal elements are doped at manganese sites, and anions are doped at oxygen sites, creating a structure with abundant active sites for lithium accommodation and stabilizing the lattice, thereby improving initial efficiency, specific capacity, and suppressing gas evolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If lithium-rich manganese-based positive electrode materials are used, then high discharge specific capacity is achieved, but low initial efficiency, low specific capacity, poor cycling performance, and high gas evolution occur
Solution Approach 1:
The patent applies local quality by doping different elements at specific sites within the material structure: Na elements are doped at Li sites, M elements (such as V) are doped at Mn sites, and A elements (such as F) are doped at oxygen sites. This localized modification allows different regions of the material to have optimized properties for their specific functions, improving overall performance while maintaining high capacity.
Solution Approach 2:
The patent creates a composite material system with the formula LitNay[LixNiaCobMncMd]ApOq, combining multiple elements (Li, Na, Ni, Co, Mn, M, A, O) in a structured composite. This composite approach allows the material to benefit from the synergistic effects of different elements, achieving high capacity while improving cycling stability and reducing gas evolution through the combined properties of all components.
2Quantity of substance
If lithium-rich manganese-based positive electrode materials are used, then high discharge specific capacity is achieved, but low initial efficiency and high gas evolution occur
Solution Approach 1:
The patent converts the harmful anionic redox reactions that cause gas evolution into beneficial effects by doping A elements (such as F) at oxygen sites. This doping stabilizes the bonding between transition metals and oxygen, effectively suppressing oxygen release during charging at high voltages. The harmful gas evolution is thus converted into a controlled process that maintains high capacity while reducing harmful emissions.
3Quantity of substance
If Na element is doped at Li sites to increase Li active sites, then initial efficiency and specific capacity are improved, but structural stability may be compromised due to volume and stress changes
Solution Approach 1:
The patent applies beforehand cushioning by doping M elements (such as V) with high valence or large ionic radii into the bulk phase at Mn sites before electrochemical cycling begins. These doped elements act as pinning points that preemptively stabilize the lattice structure, preventing excessive volume changes and stress during subsequent Li/Na deintercalation and intercalation processes. This prior stabilization allows the material to accommodate increased Li active sites while maintaining structural integrity.
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 lithium-sodium composite manganese-based material enhances initial efficiency, specific capacity, and cycling performance while reducing gas evolution, making it suitable for high-capacity and long-lasting batteries.
Implementation Method 1
Na element is doped at Li sites with partial occupancy, and in addition to Ni and Co, an M element is doped at Mn sites, while an A element is doped at oxygen sites. A structure formed by Na element with transition metal elements such as Ni, Co, and Mn contains numerous vacant active sites capable of accommodating Li
Implementation Method 2
doping M elements, such as V, with high valence or large ionic radii, into the bulk phase as pinning points can stabilize the lattice after significant Li/Na element deintercalation
Implementation Method 3
doping A elements such as F in the bulk phase can stabilize bonding between transition metals such as Ni, Co, and Mn and oxygen, mitigating substantial oxygen release caused by anionic redox reactions in manganese-rich materials at high voltages
Data Source
AI summary
A lithium-sodium composite manganese-based material and a preparation method thereof, a positive electrode plate, a secondary battery, and an electric apparatus. The lithium-sodium composite manganese-based material includes LitNay[LixNiaCobMncMa]ApOg, where 0<y≤0.2, 0.68≤t+y≤1, x+a+b+c+d=1, x>0, a≥0.17, 0≤b<0.1, c≥0.4, 0≤d<0.04, 0≤p≤0.1, 0<q≤2; M includes one or more of V, Nb, Ta, Cr, Mo, B, Al, Ti, Zr, Mg, Ce, Fe, W, or Sn, and A includes one or more of F, S, N, or Cl.