Lithium-Ion Cathode Coating for High-Voltage Cycle Stability
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Solution Overview
Problem
Existing methods for producing cathode active materials for lithium ion secondary batteries face challenges such as high energy requirements for drying, agglomeration issues leading to coarse particles, excessive alkali content causing gas generation, and insufficient cycle and rate characteristics, particularly when charging at high voltages.
Innovation Solution
A cathode active material with a covering layer comprising a metal oxide containing elements from Groups 3 and 13 of the periodic table and lanthanoid elements, combined with a compound containing Li and P, is applied to lithium-containing composite oxide particles, using a process involving separate contact steps with specific aqueous solutions followed by heating to form a stable and efficient cathode active material.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a treated surface layer is formed using conventional methods, then cycle characteristics and rate characteristics are improved, but large amounts of water must be dried requiring high energy input
Solution Approach 1:
The invention changes the chemical composition parameters of the surface layer by incorporating specific metal elements (Al, Ga, In, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Ca, Sr, Ba, Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) in controlled amounts to achieve the desired surface properties without excessive water drying
Solution Approach 2:
The invention creates a composite surface layer combining lithium-containing composite oxide particles with specific metal compounds to achieve both improved cycle characteristics and reduced drying energy requirements through optimized material composition
2Reliability
If conventional surface treatment methods are used, then cycle characteristics are improved, but particle agglomeration occurs forming coarse particles
Solution Approach 1:
The invention controls the atomic ratio of metal elements to lithium in the surface layer within specific ranges (metal element: 0.01-0.5 mol/L, lithium: 0.5-2.0 mol/L) to prevent agglomeration while achieving desired surface properties
Solution Approach 2:
The invention applies surface treatment with specific metal compounds only to the surface region of lithium-containing composite oxide particles, creating a differentiated structure where the surface has improved stability while the core maintains its original properties
3Reliability
If lithium phosphate compound and Al2O3 are mixed, then lithium ion conductivity and thermal stability are improved, but excessive alkali causes gas generation
Solution Approach 1:
The invention optimizes the atomic ratio of phosphorus to metal elements in the surface layer (P/metal element: 0.1-0.5) to achieve improved lithium ion conductivity and thermal stability while preventing excessive alkali formation that would cause gas generation
Solution Approach 2:
The invention removes or neutralizes excess alkali components during the surface treatment process by controlling the chemical composition and ratios of reactants, preventing harmful gas generation while retaining beneficial effects
4Quantity of substance
If charging is conducted at high voltage, then discharge capacity per unit mass is improved, but cycle characteristics deteriorate
Solution Approach 1:
The invention applies a protective surface layer with specific metal element composition to the surface of cathode active material particles, creating a stable interface that protects against degradation during high-voltage charging while maintaining high discharge capacity
Solution Approach 2:
The invention creates a composite structure combining lithium-containing composite oxide core with metal element-containing surface layer, achieving both high discharge capacity and improved cycle characteristics through synergistic material combination
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 solution results in a cathode active material that exhibits excellent cycle and rate characteristics even at high voltage charging, with improved productivity and reduced risk of agglomeration, while minimizing alkali-related issues and maintaining high discharge capacity.
Implementation Method 1
a first contact step of contacting a powder of a lithium-containing composite oxide... and a first aqueous solution which contains a cation having at least one metal element... a second contact step of contacting said powder of the lithium-containing composite oxide, and a second aqueous solution which contains an anion having P
Implementation Method 2
a heating step of heating, after the first and second contact steps, the obtained treated powder of the lithium-containing composite oxide to a temperature of from 250 to 700° C.
Data Source
AI summary
To provide a cathode active material for a lithium ion secondary battery excellent in the cycle characteristics and rate characteristics even when charging is conducted at a high voltage. A cathode active material for a lithium ion secondary battery, which comprises particles (III) having a covering layer comprising a metal oxide (I) containing at least one metal element selected from the group consisting of elements in Groups 3 and 13 of the periodic table and lanthanoid elements, and a compound (II) containing Li and P, on the surface of a lithium-containing composite oxide comprising lithium and a transition metal element, wherein the atomic ratio of said P to said metal element (P/metal element) contained within 5 nm of the surface layer of the particles (III) is from 0.03 to 0.45.