Oxide-Coated Cathode Particles for Low-Resistance Battery Safety
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Solution Overview
Problem
Existing secondary battery technologies face challenges in suppressing the decomposition of nonaqueous liquid electrolyte and increasing resistance due to aluminum oxide deposits, while also needing improved safety against heat generation from internal short circuits.
Innovation Solution
A positive electrode with an oxide film covering active material particles, where the film thickness and element presence probability are controlled to maintain low resistance during normal operation and high safety during short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If aluminum oxide deposits are attached to the surface of conductive material to suppress electrolyte decomposition, then battery capacity is improved, but electrode resistance increases
Solution Approach 1:
The patent applies different types of oxide films to different locations on the active material particles. An aluminum oxide film is formed on the entire surface, but a silicon oxide film is selectively formed on specific regions. This local differentiation allows the aluminum oxide to provide overall electrolyte stability while the silicon oxide regions maintain lower resistance for electron transport, thus resolving the contradiction between electrolyte protection and resistance reduction.
Solution Approach 2:
The patent creates a composite oxide film structure by combining aluminum oxide and silicon oxide on the active material particle surfaces. The aluminum oxide component suppresses electrolyte decomposition, while the silicon oxide component reduces resistance. This composite approach allows both functions to coexist, resolving the technical contradiction between improving electrolyte stability and reducing electrode resistance.
2Quantity of substance
If active material particles are used to increase energy density, then battery capacity is improved, but heat generation from internal short circuits increases
Solution Approach 1:
The patent forms protective oxide films on the active material particle surfaces before assembling the battery. These pre-formed aluminum oxide and silicon oxide films act as protective barriers that prevent future internal short circuits and heat generation. By taking preventive action in advance, the patent allows the use of high-energy-density active materials while mitigating the safety risk of heat generation from internal short circuits.
Solution Approach 2:
The oxide films serve as a cushioning protective layer on the active material particles. This beforehand cushioning prevents direct contact and potential short circuits between particles, thereby preventing heat generation while maintaining the high energy density provided by the active material particles.
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 effectively suppresses resistance increases and enhances safety by maintaining electrical conductivity and preventing rapid resistance drops during internal short circuits.
Implementation Method 1
an oxide film covering at least part of surfaces of the active material particles, the active material particles include a lithium-containing transition metal oxide, the oxide film contains an oxide of a first element other than nonmetal elements
Implementation Method 2
When the temperature of the active material particles (particles of positive electrode active material) in the vicinity of the short-circuited point rises due to heat generation, the resistance of the active material particles tends to drop abruptly
Data Source
AI summary
A positive electrode for a secondary battery including a positive electrode current collector, and a positive electrode active material layer supported on the positive electrode current collector. The positive electrode active material layer includes active material particles and an oxide film covering at least part of surfaces of the active material particles. The active material particles include a lithium-containing transition metal oxide, and the oxide film contains an oxide of a first element other than nonmetal elements. When a thickness of the positive electrode active material layer is denoted by TA, Tb<Tt is satisfied, where the Tb and the Tt are thicknesses of the oxide film at a position of 0.10TA and at a position of 0.90TA, respectively, from a surface of the positive electrode current collector in the positive electrode active material layer.