Phosphate Silicate Olivine Material for Stable Battery Capacity
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Solution Overview
Problem
Current lithium-ion batteries face issues with the amorphization of Li2MnSiO4 silicate materials during charging, leading to gradual performance loss and instability of the olivine crystallographic structure, which affects their electrochemical performance and safety.
Innovation Solution
A material with the olivine crystallographic structure and the formula A(Mm)(SiO4)(1-x)(PO4)x, where A is lithium, sodium, or potassium, M is iron, nickel, or manganese, and x is a stoichiometric coefficient between 0 and 0.8, is developed, allowing for stable insertion and extraction of element A, enhancing electrochemical properties and maintaining the olivine structure during charge/discharge cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Li2MnSiO4 silicate material is used as cathode for lithium-ion battery, then high theoretical specific capacity (325-333 mAh/g) is achieved, but the material abruptly amorphizes from the first charge, resulting in gradual loss of performance
Solution Approach 1:
The patent modifies the chemical composition parameters of the Li2MnSiO4 material by substituting Mn2+ ions with a combination of Mn3+, Mn4+, and Fe3+ ions. This changes the oxidation states and charge distribution in the material, stabilizing the olivine crystal structure during lithium insertion/extraction cycles while maintaining high specific capacity. The specific parameter changes include the oxidation degree of element M (greater than or equal to 2 and less than 4) and the stoichiometric coefficients (a, z, m, x) that define the material's composition.
2Reliability
If polyanionic materials with silicate groups are used to ensure operating safety and reliability, then battery safety is improved by limiting oxygen release, but the crystallographic structure becomes unstable during charging cycles
Solution Approach 1:
The patent creates a composite material system that combines the safety benefits of polyanionic silicate materials with the structural stability of olivine crystal structure. The material Li a Z z M m (SiO 4) 1- x (PO 4) x integrates silicate groups (providing safety through oxygen release prevention) with a stabilized olivine framework (maintaining structural integrity). The composite nature allows simultaneous achievement of safety and structural stability during charge/discharge cycling.
3Quantity of substance
If Li2MnSiO4 material is used to achieve high theoretical specific capacity, then electrochemical performance is improved, but the olivine crystallographic structure abruptly amorphizes during charging
Solution Approach 1:
The patent applies local quality modification by introducing Fe3+ ions at specific lattice positions within the olivine structure to stabilize local regions that are prone to amorphization. The Fe substitution occurs at Mn sites with controlled stoichiometry (0 < a < 1), creating localized structural reinforcement that prevents global amorphization during lithium insertion. This local modification allows the bulk material to maintain its olivine crystal structure while achieving high capacity.
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 material exhibits improved specific capacity, up to 35% greater than comparable olivine materials, and maintains structural stability, with increased ionic conductivity due to enhanced mobility of ions within the olivine structure, leading to better battery performance and safety.
Implementation Method 1
the specific capacity of the material of formula (I) remains stable during a succession of charge/discharge cycles... the group PO4 results in an increase in the lattice parameters a and b of the olivine structure with respect to the material of formula (I'), the lattice parameter c remaining constant. Without being bound by any theory, they attribute the excellent electrical properties of the material of formula (I) to an increase in the ionic conductivity resulting from an increased mobility of the ions of the element Z
Implementation Method 2
a method of manufacturing said material, said method comprising at least the successive steps consisting in: a) having: a material with olivine crystallographic structure and formula (II)... B) mixing of the first solution with the second solution so as to form a sol, C) gelation of the sol so as to form a gel
Implementation Method 3
D) pyrolysis of the gel so as to form the material of formula (II)
Data Source
Figure 1a~5
Figure 2~3
Figure 4
AI summary
Material with the crystallographic structure of olivine and formula (II) Zz'Mm(SiO4)1-x(PO4)x in which: - Z is chosen from beryllium Be, magnesium Mg, calcium Ca, strontium Sr, barium Ba and mixtures thereof, - M is chosen from iron Fe, nickel Ni, cobalt Co, manganese Mn, chromium Cr and mixtures thereof, the oxidation state of element M being greater than or equal to 2 and less than 4, - z', m and x are the stoichiometric coefficients of the chemical elements Z, M and the PO43− group respectively, and satisfy the following conditions: ∘ 0 <x<0,8, ∘ 0<m, ∘ 0<zʹ≤1−x2.